Tuning closed loop idle

I've searched and searched, with no luck.

If we have a big cam, with overlap, how do we stop burning rich at idle in closed loop?

Facts:

1. Big cams have overlap, which scavenges raw air and throws it out the tail pipe.

2. The scavenged air is read by the o2's as unburned air, which is a false lean condition.

3. The PCM tries to correct the lean conditionby adding fuel.

4. The extra fuel added makes an overly rich condition, which continues to get worse until the blms and integrators are at 160, and maxed out.

5. The scavenging continues. o2's still reads lean.

I know that we can't stop the scavenging, cause our love for the cam will not let us go back to smaller shafts.

I've seen people say to use the VE tables (lower the numbers), which will tell the pcm that the we aren't using all the air for combustion. This is incorrect. The o2 sensor is still going to read that scavenged air and try to get the o2mv to 450.

I've seen to modify the MAF sensor, which is going to be incorrect. The sensor is still going to read that scavenged air and try to get the o2mv to 450.

I've seen this answer, which seems to be the most logical, we can't tune our cars for idle in closed loop. Make it open loop.

(I'm thinking) If there isn't a way to change the target o2 mv or stoich ratio in closed loop, then we're just like the dog who chases his tail and never catches it.

Any inputs?

I think someone out there knows this answer, but hasn't published it.

D Moss

I know exactly how to do it & figured it out all on my own, so I don't know if I should say it, I used common sense & might tell you how to modify your tune if your really nice to me LOL.

Or Maybe it should be a Sticky & my name to stand out loud & proud for once LOL but I did it & car runs awesome at idle, been running like this for over 2 month now, kinda had to think beyond the ussual when I got a big cam that ran crappy at idle.

I know exactly how to do it & figured it out all on my own, so I don't know if I should say it, I used common sense & might tell you how to modify your tune if your really nice to me LOL.

Or Maybe it should be a Sticky & my name to stand out loud & proud for once LOL but I did it & car runs awesome at idle, been running like this for over 2 month now, kinda had to think beyond the ussual when I got a big cam that ran crappy at idle.


hey are those dyno numbers at the bottom of your sig current. 405

I'm all ears if you say something.

I haven't begun tuning my car yet, all I did was rebuild this monster and busted it off to break in the cam (2000rpms for 10 minutes). I didn't let the car idle but for a second or two before I shut it down, I just noticed the fumes in the shop was horrible.

I was going to tackle this, and figure this thing out for everyone if hadn't already been done.

I guess the GM847 will be big enough for my wants. Now I have to finish the final touches, crank this baby up, and begin tuning.

D Moss

Yes those numbers are current through 4.10 gears, ZR1 11inch wheels & 11.7-12.1 A/F Range, I blew a header gasket on the dyno so I stopped going, next time I'm back on the dyno I"ll bring her to 12.8-13.0 A/F & I'm sertain I'll pick up some HP maybe 415-420rwhp or so :) my TQ & power was higher throughout the RPM range & started sooner then my 847. I'll post the fix tommorow, it's quite long to explain but its so simple & obvious just tired right now, I'll do it tommorow, you'll love me :)

Matt.

You generally want to increase timing advance at idle with big overlap cams.

Try 5* more and see how it affects things.

you should do an export of your map values and calculate an average and you will find which timing it likes best. the lower the map the merrier.

I busted it back off today, and I didn't have the fumes like i had, but I also had a couple of things that I had to take care of.

It sounds good, and I think it's going to be alright, but I'm still interested in this answer. It's killing me now.

D Moss

I have a large solid roller cam. Give up now on a closed loop tune wit hstock PCM. its not going to happen. You need to make the car stay in open loop and ignore the O2 sensors.

There is one other way, you can set the PE tables to negative amounts at idle RPMs and set teh WOT table to 0% throttle at idle RPMs. However I tried this, and due to teh long term fuel trims the car eventually idled rich at an idle.

bunkers right has the fix.

VERY interested in the fix!
Let's hear it bunker....

Must be a secret...

I ran my car in open loop at idle for a period of time. It smoothed out the idle and helped low end torque. I basically made it run richer at idle, and this gave it more vacuum, like around 16 in Hg. You can do it using LT1 edit.

If I remember correctly, you set the WOT table to 0 at the desired rpms. This will force it into open loop. You will need a scanner to verify this. My motor was running in open loop from idle to around 1700 rpm. Beyond 1700 rpm, it would run in closed loop.

But, I kept on damaging or destroying cat converters because it wasn't running at the target 14.7:1 air fuel.
The only way to run a cat is in closed loop.

The CAT also needs overtemp protection which will make the engine run a little richer... and you can always measure the mixture with a lambda meter with a wideband. It doesn't have to be in the range of 10-12:1 to use a wideband... anyways... you can set the blm boundaries a bit higher to avoid the PCM to correct the problem and run by tables.

I have the innovative tech's wideband o2 sensor, so I can program for open loop if I need too. I also have a CAT less car, so that doesn't bother me either.

Ok Bunker, You've gotten all the big dogs with their ears on you,,, me, tripintaz, shoebox, dan K, highlander, and I'd imagine several others looking on.....

Hey, most of the old posts that I dug up from the search had these names in them, so I know they are interested, just as much as I am.

Thanks

D Moss

Trying to piece another part of that puzzle together.

Alright I'll tell you.

We begin by logging the data in say datamaster, find out where your long term counts hang around, say ex. 123 BLM & lower, at idle say your at 122 or whatever for longer terms. Take the highest long term count & record it, you will need to know this to tune idle, say the highest long term count durring whatever condition was 129blm for example. No problem, what you will now do is set a barrier, you do this easily.

Say at idle your MAF afg's are registering 11 AFG's, ok, go to the MAF table & everything from 7 AFG's to 18 AFGs I'd lean out, Note the frequency the original 7-18 AFGs was cuz you'll change it now, now say multiply by 90%, tune your car now & watch in closed loop what the Long term counts are now, say they went to 135 BLM, note this, go back to the MAF table & multiply the same area (frequency) for idle MAF readings by say another 90% just an example, save this & tune the car. Observe the Long Term blms at idle, say they are now 145BLM, Note, I would say a 234/242 cam 145BLM LT is good, say 240/250 cam I'd go with 155blm being good.

Now what you will do is go back to your previous highest BLM which was 129BLM, You now know that no matter what driving conditions the max your Long terms went up to was 129BLM, but now at idle they are going to 145BLM, go back to the tune & Limit the Long Term BLM correction to 130 BLM.

By limiting the Long term to 130BLM you are within your driving condition corrections & now the PCM will not correct past 130 BLM, at idle your short terms will rise to 145 BLM & the Long Terms won't compensate, the short terms will remains at 145BLM & all the time at idle only because you set a limit to the Long Term correction & altered your MAF table to achieve this.

On my cam I'm running about 155 Short term BLM & car runs great. My max Long term is set to 132 because thats what I had to have to not interfer with off idle corrections & yet stop the pcm from compensating at idle.

so a 234/242 say 847 cam I liked 145 Short term, with my cam now I like 155 short terms because of more overlap.

There you go boys, I thought of this all on my own :)

If some of you need to know how to limit the long term blms, the newest tunercat tunner has the limit option. Not the KEEP ALIVE BLM but the regular MAX BLM number is what you alter in tunner cat. If someone doesn't have this, once you figure out where you want your BLM email me your tune & I'll put the limit on to whatever to help the few first guys out.

Matt.

Actually... i have done that before... but found that the PCM got all a bit crazy with the STFT resetting and starting again and it made the car not smooth at all at idle...

Did more or less the same thing, but dealing with the injector constant... Since i've been w/o my car, i thought i will try the blm boundaries and set them up over 1200rpm and see how it went...

Anyways guess i will try all this out again.

Shouldn't be resetting at all, are we talking about the same thing bud? If you're talking boundries thats a completely different thing bro, I'm taking max/min blm LIMIT not boundries.

LMK.

I understand that... the problem i had was that my STFT did something like this:

started at 128 when pegged to the 135 limit i had set to the LTFT... then ...the stft rised rised rised rised rised.. hit max.. went to 128.... start over... rised rised rised rised.. went to 128 start over... i was WTF?

The other thing is i do not know how to make my car go into close loop faster. It appears i have a timer or something similar.

I guess i will use a GM update bin from my SPS and start from there.

again bunker.. IM NOT sayiny you are wrong at all....

i agree its the best way if it works like you describe...

Just.. that it didn't work for me with my cal.. i will try with a newer gm cal...

The other thing is.. what you did with the blms to never go over 129 that is the best idea...

I wish there were a blm blocker for the idle like there is for the WOT.

Hehe thanx yeah it works just try a different revision of tune, mine is off a 94 F-body so try that, my long terms hit 135 & the short terms stay pegged at 155 & thats how it stays thruout, I can show you a log if you like aswell.

Been there, done that, worthless. The PCM will change the tune.

but if it works for you thats awesome

Been there, done that, worthless. The PCM will change the tune.

but if it works for you thats awesome



it works for a buddy of mine. when i did it.

how can the pcm change the tune. clarify

I had thought of that before, but never tried it.

I just wish I could figure out why my wideband won't give me accurate readings at idle...then I could use a pe idle for this.

it may not give accurate readings because there is not enough flow through the sensor or because of the same problem the stock sensors have.

it works for a buddy of mine. when i did it.

how can the pcm change the tune. clarify

the long term and short term fuel trims even when the BLM correction factors were limited still wouldnt stay put and my car would go from stalling lean at idle to running a touch rich. Back them down even more and it would just stall.

but then again my cam is larger than any of yours, It just wont work for me. I use speed density and a wideband.

As for the wideband not working at an idle question......There is a setting called sample rate in my LM1 wideband unit. At idle apparently the exhaust pulses are not moving fast enough to be accuratly measured. But you are supposed to be able to slow down the sample read rate of the wideband O2 sensor for this reason. However I have not tried to mess with this yet.

Ok I'll post a log off my car later on today so you can all see.

Matt.

As for the wideband not working at an idle question......There is a setting called sample rate in my LM1 wideband unit. At idle apparently the exhaust pulses are not moving fast enough to be accuratly measured. But you are supposed to be able to slow down the sample read rate of the wideband O2 sensor for this reason. However I have not tried to mess with this yet.

I was pretty sure that it was a problem with the exhaust not moving fast enough across the sensor. Looks like I'll have to read through the manual and find this.
Thanks!

Odd, I am running a 236/242 dur. cam and do not have any issues at idle. My blm's were slightly high at idle but adding a little fuel through the individual fuel trim at idle table solved that. My idle is bumped 50 rpm over stock and my maf table is stock.

The problem isn't that, with a big cam when your fuel trim is perfect it really is too rich, the extra oxygen that passes through the overlap fools the o2s into thinking its too lean, o2s compensate until everything for the o2s is perfect while the mixture is way too rich you just don't know it because of the fresh oxygen that flies through the overlap.

Bunker, in that case I too have the problem,I thought you guys were addressing a drivability concern, I thought the fumes were normal to a certain degree(no cat). But why did my blms stop rising after adding fuel?

I have a 260/260 solid roller cam....Joe Overton himself told me Closed Loop operation wasnt going to happen, but I tried anyway and failed. Altho I have heard cams as large as the 306 can run closed loop tunes but just smells rich at an idle.

I know for a fact my car smells almost of raw gas at its 1000 rpm idle and the Wideband says it has a 18:1 AFR.......lol dead wrong. Overlap sucks at an idle but is awesome at full throttle......especially on the spray

Do you want to try out my Closed loop tune? Maybe it'll work for you? I have a pretty nasty cam on a 109 LSA & no probs here.

Matt.

So either way that we run these, the o2's are still going to read wrong to actually what is going on in the cylinders, so the only thing that we can rely on is the ole spark plug reading method.

D Moss

Do you want to try out my Closed loop tune? Maybe it'll work for you? I have a pretty nasty cam on a 109 LSA & no probs here.

Matt.

thanks for the offer, but I have no MAF or O2's anymore :eek:

I know for a fact my car smells almost of raw gas at its 1000 rpm idle and the Wideband says it has a 18:1 AFR.......lol dead wrong. Overlap sucks at an idle but is awesome at full throttle......especially on the spray


What you smell is a very high hydrocarbon count from being too lean...
18:1 afr ....ouch

I have a 260/260 solid roller cam....Joe Overton himself told me Closed Loop operation wasnt going to happen, but I tried anyway and failed. Altho I have heard cams as large as the 306 can run closed loop tunes but just smells rich at an idle.

I know for a fact my car smells almost of raw gas at its 1000 rpm idle and the Wideband says it has a 18:1 AFR.......lol dead wrong. Overlap sucks at an idle but is awesome at full throttle......especially on the spray

OH NO... DEFINETELY NOT ON THE SPRAY.. you do not want your expensive N2O to get out of the chamber... when you have n2o you do not need air perse.

What you smell is a very high hydrocarbon count from being too lean...
18:1 afr ....ouch

I can assure you its RICH not LEAN. Please tell me you are joking........

it registers 18:1 + which basically means due to the sensor being unable to accuratly read AFR at idle ( slow exhaust pulses ) it kinda goes off chart. a tip in the throttle and the AFR comes down the the 14s'. The real AFR is NOT 18:1 at an idle.

OH NO... DEFINETELY NOT ON THE SPRAY.. you do not want your expensive N2O to get out of the chamber... when you have n2o you do not need air perse.

My lobe seperation is 112, not the BEST N/A cam and not the BEST N20 cam.....however I have dyno sheets that say it LOVES N20 :D

please , no more telling me what I am doing wrong. Thankyou.

Do yourself a favor and put a sniffer in the exhaust and check the hydrocarbon counts.
I'm not joking...>>>no smiley here<<<
It will burn your eyes smell like its running rich the block learns will be maxed out [160]
160 means the ecm is adding max correction to fueltrim >>> running way too lean
108 means its making max correction taking fuel out >>> running way too rich

No at idle & mostly only at idle & really low rpm with big cams, 18:1 is ussually pretty good. The best way to check to see if your running rich or lean is with a Emissions sniffer at a shop, put it up to the sniffer & check for CO, you should have 1% CO ussually a good reading for fuel injected cars, higher is richer then normal, smaller number is leaner, CO isn't effected by overlap, CO is produced in the combustion chamber only, so even if you have fuel/oxygen escaping through exhaust the CO doesn't change since its only a product of your cobustion. Hope this helps.

BTW after carefull logging my idea didn't work, reason my idle got lots better is because if you don't let LTFT learn your idle becomes more consistant, if LTFT is maxed out at say 135 well it won't learn past that & at times the idle is more consistant, but it still runs rich because the STFT still add fuel, I thought the STFT just show you were you're at & the LTFT correct it to get the STFT back to 128, well I was wrong, if the STFT goes to say 150, its still correcting fuel because you can see when you come to a stock the o2s read low 100's & then after 5 seconds they start jumping around, so its still learning, in OPEN LOOP I'm getting 18:1 A/F & 100 for o2 readings & its were she runs real nice because the ratio in the combustion is acctually proper at that.

You see for some that don't get it, with overlap lots of fresh oxygen is being thrown out past the valves while idling & so does fuel, unfortunetly our O2 sensors & every other O2 sensor is just THAT, it only reads the O2 comming out, the extra fuel thats dumped past the overlap isn't picked up by the O2 sensors but the fresh oxygen is, so it tells you its lean while in reallity its fine if not too rich in the Combustion Chamber (actual useful fuel mixture), with stock cams barely any unburnt (unused) oxygen passes through the overlap because the duration/overlap/lift is so small barely any oxygen gets past the valves that doesn't get to participate in the actual BURN, so after combustion occurs the oxygen content is consumed & the o2's are calibrated for that to read proper A/F, when big cam comes in this goes out the window, now the only way to know if you're running a proper mixture is with an emissions tester & check your CO readings, aim for 1% at idle.


Matt.

Do yourself a favor and put a sniffer in the exhaust and check the hydrocarbon counts.
I'm not joking...>>>no smiley here<<<
It will burn your eyes smell like its running rich the block learns will be maxed out [160]
160 means the ecm is adding max correction to fueltrim >>> running way too lean
108 means its making max correction taking fuel out >>> running way too rich

incase you missed it, I run Speed Density mode with a wideband 02 setup.:)

I have no MAF or stock 02 sensors.....which means I have an open loop tune and there is no Closed Loop or learning occuring in my PCM.

Sorry Bunker, I didnt wanna burst your bubble but I went down that road before trying to get a closed loop tune.....and you see where I ended up. :(
Its a pain getting speed density dialed in but the wideband makes it easy and once its done you will be kicking yourself for messing with a MAF sensor and Closed Loop for so long ;)

altho at the current moment I put my MAF back on because I wasnt done with my speed density tune and I blew a header gasket so the wideband is off. once I get my new headers from Jet Hot ( long story but its their fault i have blown 4 header gaskets in 8 months) I will be going back to finish up. :p


EDIT: I just thought of something bunker, what If you put the car in WOT mode at an idle ? This would disable your STFT's and editing the BLMs like u did would limit the LTFT's.

Another Idea is if you have the newest version of LT1 Edit you can lock your BLMS at 128 at WOT. by setting the PCM to see IDLE as a WOT mode you could actually disable all fuel learning this way, once the LTFTs are LOCKED at 128 and the STFTs are not used in WOT mode its not going to try and add/subtract fuel. and you can use the PE table to take out or add fueling at an idle.

Hehe Been there done that, I have the newest version of tunercat/LT1_edit version 2.2, tried the WOT PE table mode, fergot what it was but I coudn't get the car to run right, I think its cuz the PE table went in too big of RPM increments making it impossible to run right, I don't see why you didn't like the MAF though? I am definetly thinking of ditching the o2's but you need the MAF for a few things, see problem with running no MAF is atmospheric conditions will greatly affect your tune, its like in the old days people would tune their car but then in a month when it gets hot outside now they are running too rich, atleast with the MAF you don't run into this problem since if you get her tunned right the first time, & it gets hot outside the MAF will lean the mixture out, no need for o2s to take care of atmospheric changes, the hotter air causes the maf to register less AFGs leaning the mixture out, so you can get away without o2s & still be tuned near perfect durring all conditions.

Just a thought, why did you get rid of the maf?

matt.

well for couple of reasons
#1 its a restriction
#2 it doesnt allow me the fine tuning I can get by using the VE tables as the primary fuel controls.
#3 we believe its responsible for the choppy dyno graph and weird fueling issies at 6600-7000 RPM range.

Its also a myth that Speed Density mode cannot correct for weather differences. Granted its not as good as a MAF but it uses an equation with the IAT sensor to do some corrections. But I have a wideband setup and can do minor tuning for temp changes anyhow. A kid on here NASTY SS with a pretty hard core LT1 like my own turned me on to Speed Density and Wideband :) trust me, once you go Speed Density you never go back to the MAF.

I'm starting to think the same, care to share your VE tables with me :)? I think I'm about fed up aswell.

Matt.

If you have tunercat, send it to me too.

I was going to put my input on my desktop dyno, and it will tell me the VE for my combo, and I want to see how it corresponds with your's, of course it's gonna have differences due to cam and head flows, but a general idea.

Fellas, I didn't want to stir up a hornets nest when I began this post, but I'm glad to see the answer. I'm not glad for what the answer is, I'm just glad that I'm not going to try and chase down the goast that everyone else has found out that does not exist. Kinda like looking for that pot of gold at the end of the rainbow, or that cure for my fat old ladies stinking feet, which doesn't exist. :eek:

Though once we was told that water and vinegar will clean lots of things. ;)

D Moss

Yes, I have engine analizer which tells me the same thing

Lets see Tripaz :)

Yeah EAPro is a good program... i have it too, but i dont tune the VEs that way though...

Yeah lol hence why I'm asking Tripaz for his :)

You want to know the correct and only way to tune ve?

well my tables are not completely tuned yet, but i will show you what i got for now :)
Remember I didnt get a chance to make alot of tuning correction before I found my header gasket leak, but this will get you big cammed guys in the general area.

THIS TUNE ONLY SHOWS VE TABLE CHANGES, cant give you all my entire tune...hehh

http://www.tripintaz.com/file/TazVE.LT1

Must be LT1 edit. :(

<<<couldn't view it

Must be LT1 edit. :(

<<<couldn't view it

Here is the program to convert .LT1 files to .BIN, it also converts .BIN to .LT1 I think.

http://www.tripintaz.com/file/TuneConv.exe

:D

There is something wrong with the file, I tried opening it & its all corrupt in Edit, then converted it to bin & can't open it in tunercat either.

Maybe I should have mentioned that its an OBD2 .LT1 file. So tunercat cant view it and neither can OBD1 version on LT1 edit.

Ill have to make pictures of my tables and get them on here, i should get them up by tomorrow.

Hey Everyone,

I'm very tempted to stay quiet here, but I'll see if I can help a little bit.

David, you original post asked if there was a way to have a big cam idle in closed loop without adjusting the fueling way out of wack. The short answer you alluded to is correct, the closed loop feedback system isn't going to handle a big cam. This is due to the unburnt oxygen causing a false lean reporting from the O2 sensors, causing the downward spiral of the pcm dumping more fuel.

So since that answer isn't what anyone wants to hear, the real question is: "How can I get my car idling as smooth as possible with this large cam?" If the answer isn't closed loop, then it must be open loop (simple boolean logic there) Now that we've decided open loop, do we want open loop all the time or just some of time? Supposing the O2s report fine once the engine gets over 2000 rpm and you'd like the benefits of a closed loop system at that point, I'd say going open loop idle would be the way to go. The closest we have is Power Enrichement idle.

Side note: One thing that can help to smooth out lower rpm's is slightly advanced timing. I say slightly because too much timing can cause NOx emissions to spike. Really depends on the cam and the setup. Bigger displacement engines are more efficient at lower rpm's so a larger cam often behaves much nicer in those setups. I'd keep closed throttle spark below 28 degrees on a 350 LT1 for reference.
Back to open loop idle. Thought of this years ago and it's worked well for lots. Simply adjust you WOT vs TPS to 0 at the lower rpm range that you want to run open loop at. We'll get to PE vs. RPM adjustments in a sec. As Bunker mentioned the PCM will continue to try and learn, given enough time in WOT mode you will see the BLM's start to trim fuel. How can this be? Well, PE mode can exist in both open loop and closed loop (since they just state the preparedness of the O2's for feedback.) So, given this fact we need to lock the BLM's in PE mode. I wrote the BLM locker years ago, can be used on OBD1 .LT1 and .BIN files. here's the download location:

http://www.carprogrammer.com/WOT_BLM_Locker/

After applying the BLM locker, the BLM's won't move during PE Idle. Now the PE vs. RPM table can be used to fine tune AFR for idle. I can adjust WOT AFR by a tenth of a point using the PE vs RPM table, so nailing down idle will be possible. Bunker/ Matt was correct when he pointed out oxygen can't be used to meter combustion since it's not a byproduct. CO isn't a bad choice, but I'd recommend CO2 since maximum Carbon Dioxide indicates peak combustion efficiency, take a quick look here for a chart and brief explanation why:

http://www.carprogrammer.com/Z28/PCM/emissions/EMISSIONS%20h56.pdf

So if you've got access to an emissions place with an infrared 5 gas analyzer you're set, but if not like Matt said you can use a CO meter, which are much less expensive. Anyone remember the old gas analyzer that people used on motorcycles? They're under $100 and all over Ebay. I have a similar model pictured here:

http://www.carprogrammer.com/Z28/ExhaustAnalyzer/

Since it's measuring CO, and CO levels drop off past 14.7:1 (stoich) the best bet is to find where it's above 2%, then lean until it starts to drop down to .5 - 1%. That will be the best someone can do that doesn't have access to an emissions station. It doesn't really take that long, just a couple flashes should have you there.

Hope this helps,
-Christian

To add a couple things:
For the ODB2 crowd Ken made the BLM locker available as part of recent OBD2 LT1 edit releases, so you'll be able to get it there. Dunno if he's addressed the LS1 Edit crowd with that yet.

On an OBD1 car I recommend a factory MAF setup and factory MAF tables. misreporting airflow just causes more adjustments in other places, it doesn't change the feedback of the O2's. The pcm will adjust, or the user will need to in other places. Stock MAF's have been good on lots of 400-500+ rwhp NA setups and many 700+ Forced Induction setups, it's been proven by many people they don't present a restriction, but everyone is entitled to their own beliefs, just my experience. VE tables aren't used in 94-95 MAF setups if the MAF is reporting correctly, so don't waste any time there.
Hope this helps,
-Christian

Exactly, the VE table is only referenced to by the PCM is the MAF fails in 94-95 OBDI cars. As for PE idle tunning I figured I'd try that a while back but ran into a problem, I think it was getting it to work properly you needed to alter the WOT TPS table so your in PE mode at 0% TPS, prblem is if I'm ideling at 1000rpm the next WOT cell was 1200, then the next was 1600, so if my WOT table was set to 0 from 400-1200 RPM, between 1200-1600 rpm would be a problem because the car would get in & out of PE mode unexpectedly, cuz at say 1400 rpm at 0 % you would be out of PE mode but at 30% you would be in PE mode because 1200 being at 0 & 1600 being at 60% between the two the PCM would just average out a number, its not a problem if you idle at 800 rpm, but if you idle at 1000 the best bet was to set the 1200rpm mark at like 40% or so, dunno its that which messed me up but I'm sure there is a sweet number in there if you can figure how you drive.

Matt.

I believe I'd like running like this better.

I want to keep the closed loop function since it works great cruising.

Being in PE doesn't bother me at idle, as long as I can dial it in and not throw gas out of the tail pipe.

I'll try the PE version, and see what happens.

I'm still going to change my VE tables, cause I've seen on this site where if you change the VE to closely match your engine's effeciency, then when your car does need to use the speed densitiy mode, it will be right.

I also have to change my MAF tables since mine has been ported.

KEEP THIS GOING!!! This is one great educational post for everyone.

Thanks

D Moss

Life is too short to spend time tweaking VE tables that won't be referenced, but hey it's a free country :)

Ditched the ported MAF and get a nice stocker, it's one less thing to elliminate when you're trying to figure out why you AFR or BLMs are off.

Bunker/ Matt you've got a good understanding of the interpolation going on with values between table values, use it to your advantage. If you need to set 1600 to 0% TPS that's fine too. I can't see spending much time cruising below 2000 rpm in a big cam car anyway.

Give it a try, share your experiences.
-Christian

Well I am going to have to disagree, PE mode is not used in OPEN LOOP. I use an OPEN LOOP tune on my car and there are ZERO Long Term or Short Term fuel trims. Changing the PE tables on the dyno results in ZERO change of fueling at WOT.
And VE tables changes DO make a difference in OPEN LOOP tunes, but people are under the misconception that changing the VE is going to drastically change the fueling, but this is not the case. But I have experience in OBD2 tuning, not OBD1. However I am pretty sure PE is NOT used in OPEN LOOP on OBD1 either.

Life is too short to spend time tweaking VE tables that won't be referenced, but hey it's a free country :)

-Christian


if i change my ve tables with the maf pluged in, my blms will drasticly change. so why do people say that the ve tables are not used when the maf is fuctioning properly.

Simply adjust you WOT vs TPS to 0 at the lower rpm range


where is this table in tunercat. i have "kick down mode enable tps threshold" and "kick down mode disable tps threshold" in the constants tables.


i found the wot rpm table

Well I am going to have to disagree, PE mode is not used in OPEN LOOP. I use an OPEN LOOP tune on my car and there are ZERO Long Term or Short Term fuel trims.

Open/ Closed loop is a separate boolean variable from power enrichment/ non-power enrichment boolean variable. Closed loop indicates the O2 sensors are warmed and can be used for feedback adjustments. Power Enrichment causes target AFR to switch from Stoichiometric 14.7:1 in closed loop, or open loop table value to adding extra fuel as per the PE vs RPM and PE vs Coolant temp.

Changing the PE tables on the dyno results in ZERO change of fueling at WOT.

Changing the PE tables is exactly how you dynotune WOT. That's the purpose of having the tables there. Yes some people alter the MAF tables to misreport the airflow, but that's a bit of a rough hack to put it bluntly. Tune with the PE tables allows me to dial in WOT AFR dead on usually within three dyno spins. It allowed me to nail the AFR like this:

http://carprogrammer.com/Z28/dynos/ChristianNewMotorAFR20030801.gif

And VE tables changes DO make a difference in OPEN LOOP tunes, but people are under the misconception that changing the VE is going to drastically change the fueling, but this is not the case. But I have experience in OBD2 tuning, not OBD1. However I am pretty sure PE is NOT used in OPEN LOOP on OBD1 either.

Here's where it's inportant to know the differences between OBD1 and OBD2. OBD1 (94-95) doesn't use the VE tables unless the MAF fails tests. OBD2 includes the VE tables in the fuel calculation to verify MAF readings, both in Open Loop and Closed Loop operation. Again think of Closed loop as the O2 sensors being warmed up for a feedback system.

Hope this helps,
-Christian

if i change my ve tables with the maf pluged in, my blms will drasticly change. so why do people say that the ve tables are not used when the maf is fuctioning properly.

VE tables are used in the fueling calculation for OBD2 cars, that's all. What you've seen is normal.

Simply adjust you WOT vs TPS to 0 at the lower rpm range

where is this table in tunercat. i have "kick down mode enable tps threshold" and "kick down mode disable tps threshold" in the constants tables.

i found the wot rpm table

On the OBD1 $EE definition Tunercat calls this table: %TPS Threshold for WOT vs. RPM (low cool) - ( High cool isn't populated or used)
stock values are 66% TPS to enable PE all the way up to 3200 RPM.

Hope this helps,
-Christian

Open/ Closed loop is a separate boolean variable from power enrichment/ non-power enrichment boolean variable. Closed loop indicates the O2 sensors are warmed and can be used for feedback adjustments. Power Enrichment causes target AFR to switch from Stoichiometric 14.7:1 in closed loop, or open loop table value to adding extra fuel as per the PE vs RPM and PE vs Coolant temp.


on OBD2 cars, PE tables are not used in OPEN LOOP. Instead the pcm refers to the OPEN LOOP vs KPA vs TEMP AFR tables. I have data logs that even show the PCM refers to this table for target ARF under WOT as well as part throttle fuel while in OPEN LOOP.

I run an open loop OBD2 tune. There are no fuel trims happening, and the PE tables are not used at WOT. And the target AFR always matches the values I have set in my OPEN LOOP AFR table.

on OBD2 cars, PE tables are not used in OPEN LOOP. Instead the pcm refers to the OPEN LOOP vs KPA vs TEMP AFR tables. I have data logs that even show the PCM refers to this table for target ARF under WOT as well as part throttle fuel while in OPEN LOOP.

I run an open loop OBD2 tune. There are no fuel trims happening, and the PE tables are not used at WOT. And the target AFR always matches the values I have set in my OPEN LOOP AFR table.

Interesting, I have dynotuning experience with OBD2 LTx's and LSx's that has shown otherwise, that's all I'll say. If the PE vs. RPM table isn't referenced, then how do you control AFR at different RPMs? Yes, the open loop table is a starting point for fuel calculations, but hitting WOT in open loop does cause a lookup to the PE tables for calculation. Again, just my experience.

Here's a quick way to test if the PE vs RPM table is referenced. Max out the values in the table, forcing lots of fuel to be added at WOT. Take the car for a spin around the block, floor it and watch how pig rich it runs after the change.

Not saying what you've observed is wrong, just sharing my experience, that's all,
-Christian

I am still skeptical about the roughness when entering from open loop to closed loop, which was i have not used this method...

Christian, can you post your feedback on if you feel the car surge, kick or give ANY indication that has changed modes?

on 94-95 cars VE tables are not used if MAF is working correctly, VEMaster never worked for obdi with maf...

VE tables are used in the fueling calculation for OBD2 cars, that's all. What you've seen is normal.



but im running a obd1 conversion.




On the OBD1 $EE definition Tunercat calls this table: %TPS Threshold for WOT vs. RPM (low cool)


so udjust this table to 0% at what ever rpm i idle at. and this will set pe mode at idle, and when i go off idle it will do as normal. correct

correct, only problem is if you idle at 1000rpm, the next bracket is 1200rpm, if you set that to 0% then if you cruise between 1200-1600 you will be going in & out of PE mode depends on your TPS position which would kinda suck :)

correct, only problem is if you idle at 1000rpm, the next bracket is 1200rpm, if you set that to 0% then if you cruise between 1200-1600 you will be going in & out of PE mode depends on your TPS position which would kinda suck :)

Why not idle at 900rpm?? what kind of cam are you guys running to have such a high idle.. i just hope i dont have problems with my new cam

I am still skeptical about the roughness when entering from open loop to closed loop, which was i have not used this method...

Christian, can you post your feedback on if you feel the car surge, kick or give ANY indication that has changed modes?

on 94-95 cars VE tables are not used if MAF is working correctly, VEMaster never worked for obdi with maf...

Yes, other than datalogging, you can hear the engine sound change when closed loop is entered (depending on setup, cam, displacement, etc.)
Open loop tends to be a bit smoother sounding than closed loop, it's a slightly richer mixture, not as erratic as closed loop (again, depending the build, a hotcam sounds much different from a CC306)

-Christian

im over a cc306 already...

but im running a obd1 conversion.


Okay, then I have done the experiment for you (with my car even.) I can promise you PE mode can be enabled during open loop.


so udjust this table to 0% at what ever rpm i idle at. and this will set pe mode at idle, and when i go off idle it will do as normal. correct
[/QUOTE]

yes, and you might want to adjust the neighboring cells like bunker was saying. If you idle at 900 rpm (like most do) then set 800 and 1200 cells to zero.

It isn't a drastic change if you've calibrated the PE idle to a reasonable mixture (say 13.5 - 14.0:1) I did it for a long time with my Ultradyne cam, no problem whatsoever.

-Christian

Highlander, you are running your 383 which doesn't need to idle as high with a big cam, I like mine at 1000 cuz its smoothest there, my cam is bigger then the cc306 or 847 & its on a 350 stock LT1.

Cmillard, how did you experiment that PE mode is entered in Open Loop? I'm pretty sure its ignored, if you datalog with say TTS DATAMASTER you can see the PE mode is enabled in OPEN LOOP, but what you don't see is if its acctually doing anything, just so you know, when I was dynotunning my car here were my result:

PE table around 5 point A/F= 12.0
PE table around 0 points A/F = 12.0
PE table at -10 pionts A/F = 12.0
Said **** & and went PE table -30 points A/F=12.0

Even though TTS showed that PE mode was being enabled, those were my inputs from 5k+ RPM.

Hope this dyno experiment with open loop helps some :)

Interesting Matt. I forced open loop by setting closed loop enable temp to an impossible number. I added +30 to all the PE vs RPM values (to make sure I'd feel it.) Went down the road to a low traffic highway turnaround, then stomped it. Sure enough, ran rich enough for smoke out the back, injector duty cycles were much higher then same run with normal PE values. I posted my experiment several years ago on the LT1 edit list, and several people chimed in with similar experience. That's how we determined in concensus it was definitely affecting fueling. I can go look in the disassembly as well, I don't remember there being any exceptions to power enrichment (like jump out if in open loop mode.)

Just sharing my experience,
-Christian

Maybe in Open loop anything in the negative numbers is ignored?

Matt.

Also, when you did that, was BLM enabled? Cuz mine wasn't since my BLM enable was set to 74*. Maybe its not Closed Loop, maybe if it BLM isn't enabled the PE table is ignored?

chris i was refering to the use of the ve tables. i can change my ve tables and blms change drasticly. and yall are saying its not used on obd1 and it sure affects my cars blms and im runnign a obd1 pcm.

Interesting Matt. I forced open loop by setting closed loop enable temp to an impossible number. I added +30 to all the PE vs RPM values (to make sure I'd feel it.) Went down the road to a low traffic highway turnaround, then stomped it. Sure enough, ran rich enough for smoke out the back, injector duty cycles were much higher then same run with normal PE values. I posted my experiment several years ago on the LT1 edit list, and several people chimed in with similar experience. That's how we determined in concensus it was definitely affecting fueling. I can go look in the disassembly as well, I don't remember there being any exceptions to power enrichment (like jump out if in open loop mode.)

Just sharing my experience,
-Christian

Lets say you tuned your car in closed loop mode using the PE tables. Then you force your car into OPEN LOOP and now you say its pig rich. Well teh stock numbers in the 100 KPA table are at 12.5:1 target AFR instead of the 14.7 that closed loop targets. closed loop, When going WOT the pcm uses a 14.7:1 target fuel but then refers to teh PE tables to add/subract fuel for WOT operation.

I didnt want to come out and say it, but PE tables are NOT used in OPEN LOOP. I think you have overlooked or mistakenly taken the open loop 12.5 target AFR as going in to PE mode.

I have data logs that show during WOT ( since my target AFR @100 KPA in the OPEN LOOP fuel tables is 13.5 ) the PCM has a 13.5 target AFR, changing the PE tables did abosolutly NOTHING in OPEN LOOP mode. Again I hate to say you are wrong, but in this case I cannot just let if go when you are mis informing the other tuners that are trying ot get reliable information from this thread.

Listen to TaZ folks, PE tables are NOT USED in OPEN LOOP. If you still have any doubts call Carputing themselves or better yet call Joe Overton.

Thankyou,
TaZ

http://carprogrammer.com/Z28/PCM/Analysis/open_and_closed_loop_WOT_testing.txt

This is off Christian Millard's site on LT1_edit forum by Schube. He seems to agree with me.

if you use the pe tables for closed loop tuning at idle, well what about the wot pe use if you program the pcm for 12.8 to 1 at wot in the pe tables then isnt that what its going to shoot for at idle. thats not near 14.7. and you dont want to run 14.7 to 1 at wot.



EDIT:

nevermind

thats where the rpm pe table comes in. sorry.

Well at least in my car the VE table is NOT used and the PE table is NOT used in Open Loop...

I had to change the open loop table when we tried dynoing the car w/o an O2 sensor because we were using a wideband there.

Yeah same here, maybe different revisions have different ways of doing things but like TripinTaz says, in my car aswell, the PE tables are NOT used in OPEN LOOP, I tried it on the dyno, going from 0 to -30 & the A/F didn't change a bit, also my VE tables ARE NOT USED in closed/open loop unless the MAF is disconnected.

Matt.

http://carprogrammer.com/Z28/PCM/Analysis/open_and_closed_loop_WOT_testing.txt

This is off Christian Millard's site on LT1_edit forum by Schube. He seems to agree with me.

CMillard IS Christian Millard ;)

I have not tested it but it was my understanding that the PCM used the richer of either two values, the PE tables or the AFR table.

If I used WOT in open loop I'd almost be tempted to start testing :D

CMillard IS Christian Millard ;)

I have not tested it but it was my understanding that the PCM used the richer of either two values, the PE tables or the AFR table.

If I used WOT in open loop I'd almost be tempted to start testing :D

Hehe, I love it when the internet goes full circle. Gotta love it when you're corrected by your own test documents :^)

This is indeed the testing I did back in the days that I was talking about earlier. Looks like my brain isn't remembering things as well as it used to ;^) I should have known I would archieve somewhere on Carprogrammer.com man, I need to index that site.

My apologies for remembering things differently, now if I could just remember where I put down my crackpipe. ;^)

Have a good night guys, looks like this thread is done.

-Christian

lol CMillard, I didnt even know that was you're site !

But I knew you had avid knowledge of Lxx_Edit and couldnt figure out why you were saying what you were saying. But Im glad we can keep a friendly conversation and not make it into a flame war thread.

P.S...Crack is bad lol

Hehe yeah crack is bad. I'm tunning Open Loop now & like it a lot better, but I have a question now that everyone is on here, I friend my PCM today & borrowed my friend's PCM into which I uploaded my exact same tune into, now the problem I'm having is when I come to a stop the idle drops below preset idle & comes back up, also when I let off the pedal if I'm deceling at 2500rpm the rpm will drop like a rock if I put the clutch in. Now I never had this problem with my old pcm, I had it tuned so while I'm driving my idle was at 1400rpm or so & when i came to a stop it would go down to 1000rpm which is lovely cuz even if I'm deceling & pushed the clutch in the rpm wouldn't sky dive, it would just come down to 1400 where it would stay until I stopped. My last tune I did lots of IAC FOLLOWER vs.MPH table alteration but it seems like with this PCM it doesn't listen to anything I put into that table??? The PCM came out of a 95 Caprice LT1, it can't be different, I dont get it, it doesn't seem like the IAC is bad cuz it can keep an idle, I also tried turning up the idle screw but the PCM doesn't care, its almost like it tries to idle at any speed at 1000rpm which it shouldn't! Could frying the last PCM could have upset the IAC or something? I also noticed that with my old PCM while I"m moving NOT in gear & TPS at 0% my iac count was at 109 or so, now its at 86, so its got to be that the PCM is commanding to lower the idle, are some PCM's acctually different in that sense? I'm weired out, I bet anything its trying to stay at 1000rpm even while moving.

Matt.

When going into OPEN LOOP tune the car uses the OPEN LOOP AFR tables for all fueling. So your fueling has definatly changed from what you had in CLOSED LOOP mode. There are no fuel corrections made in OPEN LOOP mode so it takes more effort to tune correctly. This sound like the car is not getting enough gas making it want to stall out on decel with no load.

Are your MAF tables stock ?? This is highly recomended on an OPEN LOOP tune.

I would suggest data logging your car to pinpoint the KPA and engine temp this is happening in, then going to your OPEN LOOP AFR table and adding fuel in this area and see if it improves.

The only way to really tune the MAF, VE, Maf being stock or not is to have a wideband and make sure that what its displayed in the AFRx10 table is what you get in the wideband. Period. The injector and offsets are dead on and that you tune the MAF and or VE tables so that it gets where it should be. Later when you want to be a little richer or leaner you know exactly what to expect out of the car when you change the VE table and not just do some conversion. Granted it will take a lot more time but hey, this is not a race to who tunes faster.

But why would the PCM IAC counts be at 87 or so if its stalling out? I've tried playing around with the fueling, yes I altered my Open loop table a lot but at idle I try to run her leaner because I found she runs better this way, if I crack open the TB blades it seems the PCM keeps wanting to close the IAC even on decel even more, I ran her with the same open loop tune on the other PCM with no problems, on the other PCM my iac was at 109 on decel or so, so the PCM was trying to keep the car from stalling, but with this pcm on decel its at 87 & if I crack the blades open more she closes even more so its doing it on purpose. I finally put in "28" into all my IAC follower tables & she seems ok but I didnt' need those kind of settings with my other PCM, this is stupid.

BTW at cruise what AFR do you aim for? Like do you use a wideband or something to know for sure? like how would you know if your running lean to the point where the headers are glowing or something at cruise, I mean o2's are hard to read when its a bit lean, mine jump around at most, & at idle they stay at 80mv or so, but I find its fine at idle with that voltage since my cam is big & on a 109. What are you o2's reading at idle? It seems that if I run the o2's higher voltage then that at idle the car doesn't run as smooth.

Matt.
Matt.

I have never understood why you guys attribute a "she" to the car... a femenine car???

anyways... make sure your IAC counts are in the vecinity of 30-50. so the pcm will have room to adjust.

Bunker do you have Cat conv?

No cat-conv, the PCM can go all the way to 160 if she needed more air but she doesn't, its weird how the same tune in a different PCM is acting totally different, I mean all pcm's are the same!

BTW the "SHE" attribute is sweet :)

In all honesty, your stock O2 voltages are USELESS on a large cammed car in my opinion. I have never used these to tune, they only plug the holes in my headers. they are worthless.

Since you said u tried changing the fueling and it didnt work, are you sure that you copied your CLOSED THROTTLE SPARK ADVANCE table to the new PCM file ?

As far as the throttle blades go, you need to set them up so that when your car is in neutral at idle the IAC reads about 50, and with the A/C on the IAC should go to around 80. If you set the IAC too high or too low it wont have enough room on one side to maintain the idle.

I have more then enough room, at idle I'm at 70 or so, I can't crack the blades open anymore, I'm using the holley TB so it doesn't have any bypass holes, she ran perfect with the old PCM thats the thing & the IAC counts can go all the way to 160 if they felt like it but the pcm chooses to be stupid for some reason, & yes its the identical tune just uploaded into this pcm.

BTW I use the o2's just to see if I'm not too rich since if you rich on the o2's with a big cam then you're really rich IMO :) at idle my o2s are at 80mv which would be lean on a stock engine but seems fine with mine, I think that equates to something like 18:1 A/F.

What about if you go into closed loop mode ? does it do the same thing?

Did you try this same tune in your old PCM in open loop mode ? or just closed loop ?

The only way to really tune the MAF, VE, Maf being stock or not is to have a wideband and make sure that what its displayed in the AFRx10 table is what you get in the wideband. Period. The injector and offsets are dead on and that you tune the MAF and or VE tables so that it gets where it should be. Later when you want to be a little richer or leaner you know exactly what to expect out of the car when you change the VE table and not just do some conversion. Granted it will take a lot more time but hey, this is not a race to who tunes faster.

Well said. Experimentation does take time, and that's the only way to do it, ever setup is different. One component that is getting undermentioned is spark advance. This where an infrared exhaust gas analyzer is key, but most tuner shops don't have them (starting price range ~$3000) You can find them at emissions testing locations, but getting "tuning time" at an emissions station isn't going to happen at most location.

EGT's can also be very useful, but still aren't commonly used when tuning our cars (I'd love to see that change.). They lack instant response, but they can help greatly with tuning. For example if you add more timing and exhaust temperatures continue to decrease, then you know you're headed in the right direction. Unfortunately too much timing will cause NOx emissions to rapidly go up, and only a 5 gas analyzer is going to tell you that.

Hope this helps,
-Christian

(wish I had an 8 EGT setup, that would be fun to play with.)
(p.s. sadly cylinder balance tables aren't referenced at WOT, but that can be changed :^)

[QUOTE=bunker]I have more then enough room, at idle I'm at 70 or so, I can't crack the blades open anymore, I'm using the holley TB so it doesn't have any bypass holes, she ran perfect with the old PCM thats the thing & the IAC counts can go all the way to 160 if they felt like it but the pcm chooses to be stupid for some reason, & yes its the identical tune just uploaded into this pcm.
QUOTE]

Hey Matt,

I've been where you're at. I've blamed it on bad IAC learning in the past. It's really annoying when you throw in the clutch and the idle drops so fast it almost stalls. Do a search for IAC relearn procedure, that should help out. It's not the PCM, use the stock follower tables just to prove that point.

Disconnect the battery, resetting the pcm, make sure the throttle is closed when starting it the first time, give the IAC a chance to learn. The IAC could be kludged up with carbon, but I doubt it, since it was just fine.

Give it a try, let us know how it works out,
-Christian
(a.k.a Christian Millard ... a.k.a. Puff puff give)

(p.s. sadly cylinder balance tables aren't referenced at WOT, but that can be changed

and how do we do that if you care to share. :D

Wow I didn't know the off idle tables weren't referenced at WOT, learn somthing new everyday. Needless to say, I got it to run ok I just cranked the TB blades more & put 28 throughout the table, its running perfect again, but with different TB opening & different values in the IAC tables which weirds me out.

Glad to hear it's behaving now Matt. Damn irritating IAC's, sometimes no rhyme or reason to it.

I suspected the off cylinder balances weren't used when I couldn't get the AFR balanced between the two cylinder banks using dual widebands in the headers. One side is traditionally leaner than the other, I was just trying to correct for that. I altered tables to an extreme with no difference, so I asked a person very knowledge in disassembley to confirm my thinking and he did. He also altered the code to reference a new table - WOT cylinder balance, but I never tested it. Considering he's been working with embedded systems for over 20 years if he says it will work I trust his word.

Unfortunately, like most things, to do the job right would require an 8 EGT setup. The shop actually has the EGT's, but I don't believe they have an 8 channel card to accept the input from each of the EGT's. I see Dataq just came out with one though (only $895 w/o thermocouples - ouch)

http://www.dataq.com/products/hardware/di1000tc.htm

okay, back to your regular programming,
-Christian

ASk rskrause.. i believe he had the 8 egt setup some way.

Will do, I know John up at MBA had an 8 egt setup, not sure if he still does.
Would definitely be neat to tune with such a setup.

-Christian

No kidding, I"m definetly suffering from this effect, I think this one has lots to do with drivability since if you have a split & the o2's correct for it, they might be causing more problems then there already are.

I belive this is how mine is screwy:

IDLE: LEFT O2 Richer/ Right O2 leaner
ON DECEL(fuel shut off): LEFT O2 Richer/ Right O2 leaner
PART THROTTLE: LEFT O2 leaner/ Right O2 richer
Accelerating high MAP: BOTH O2's pretty much the same, at times reversing from cruise
WOT: LEFT O2 Richer/ Right o2 leaner (950/902)

So you can see how irritating this can be, I tried swapping the injectors side to side with no difference what so ever, next is swapping the o2's around, hardly doubt it'll fix the problem, I think its the effects of a big cam & reversion is the problem, but then what about WOT runs? LOL, I notice that when I get my A/F within acceptable limits IE. 12.6-13.0 at WOT, I see this split, if I'm running rich IE. 11.7-12.2 I see not much of a split at all, this become very irritating when you try to perfect everything in your car ie. get your valve train geometry all perfect, make sure your installed heights are all the same, pushrods perfect length, use lash caps, set rockers while engine is up to temp & idling etc... I do all this to prevent such things, but what the heck.

At one time with my old setup everything started looking good one day IE both left/right bank were pretty even, but i was down on power, turns out one of the lifters poped a plunger, so a mechanically unsound setup showed up real nice on the scanner :mad:

Matt.

Yeah, chasing the perfect numbers in an imperfect situation can be an endless chore. Been there, spent too many hours of my life doing it.

Since we've got a single manifold intake plenum and short runners cylinder distribution will always be a problem. Simesed ports and our firing order doesn't help either, but hey considering the LT1 is just a late 80's version of a regular small block chevy it does a surprising good job. notice the LS1's corrected a lot of the issued addressed, but remember we easy make the same power with just a couple mods on our LT1s.

Just on a note, I've noticed over the years dynotuning that as the car gets closer to ideal timing the AFR split between the two cylinder banks is minimalized (notice my AFR above.) I assume it's no small coincedence, but thought I'd share that. Most places don't bother to install dual widebands, which is what's necessary, but I consider myself lucky to tune at Woodbridge Dynotech.

Wow cool I didn't know this, I'm going to look at a bunch of my logs & see what the timing was LOL :)

Matt.

Wow, I've been gone a week and all kind of things are happening in here.

So, If you're running a big cam and you want to run closed loop, then you're gonna be rich at idle.

Open loop is the only way to really correct the overrich problem with the big cam.

???

D Moss

Wow, I've been gone a week and all kind of things are happening in here.

So, If you're running a big cam and you want to run closed loop, then you're gonna be rich at idle.

Open loop is the only way to really correct the overrich problem with the big cam.

???

D Moss

i tried what chris said about enabling pe mode at idle and tuning that way and works like a champ. killed all the horible gas smell and idles better. and the pcm still works fine. once the car goes above 1200 rpms its back to normal.

Open loop is the only way to really correct the overrich problem with the big cam.

???
D Moss

In not so many words, yes. The second critical thing is spark advance. Bump up your closed throttle spark advance at idle rpm range from stock (20 degrees) to 26 degrees, should really clean the idle up a bit. I find vacuum will continue to increase with advance, but beyond 30 degrees the NOx smell will get to you, eyes may burn as well. Varies with size of cam of course.

Hope this helps,
-Christian

I have 36* of advance at idle & she seems fine :) don't know how I ended up with so much advance but I did, helps keep the headers cool incase I run lean at idle with open loop aswell, just trying to smooth things out, I think I'm going to go with closed PE once again & see.

BTW just wondering, what do you guys with big cams end up for numbers in the PE table for idle for reference?

Matt.

well I cant say much for the PE tables other than when you tell the PCM that closed throttle IDLE is in PE mode, the PCM assumes 12.6 as the target fuel ratio so its almost a given you will have to set the table to about -10% or so to get the PCM target AFR to 14.7 at idle. If you have a scan tool this can be verified by looking at the TARGET AFR line in your scan tool, just keep subtracting till you see it show 14.7 when you are idling. From this point you will want to either add or remove fuel depending how its running, but 1st get the PCM to make the target AFR 14.7 at idle.
Another note, if at 14.7 target AFR the car is too lean try backing the timing down a little at closed throttle idle, it all depends on your setup what works best.

I use 38 degrees of timing at closed throttle idle

Wouldnt you want it leaner than 14.7 reading off of the O2's? I thought this was the whole problem, that what the PCM saw at 14.7 was lean when it really isn't. If the PCM shoots for 14.7, o2 hits the sensor, and it throws more gas too the equation, resulting in rich mixture again. I thought it was more like 18.1. (I saw that somewhere)

BTW....I have the LM-1, so I can see what is really happening in the tailpipe, just have to know where to fix this.

Plus I thought that the PCM didn't use the o2 sensors in PE mode. If this is correct, then PE is in open loop, and there should be some tables that I can find to use to subtract the fuel during PE. (not the MAF) It's the O2's that are killing us during this time, we just have to get them out of the equation and be ignored during idle.

D Moss

Wouldnt you want it leaner than 14.7 reading off of the O2's? I thought this was the whole problem, that what the PCM saw at 14.7 was lean when it really isn't. If the PCM shoots for 14.7, o2 hits the sensor, and it throws more gas too the equation, resulting in rich mixture again. I thought it was more like 18.1. (I saw that somewhere)

BTW....I have the LM-1, so I can see what is really happening in the tailpipe, just have to know where to fix this.

Plus I thought that the PCM didn't use the o2 sensors in PE mode. If this is correct, then PE is in open loop, and there should be some tables that I can find to use to subtract the fuel during PE. (not the MAF) It's the O2's that are killing us during this time, we just have to get them out of the equation and be ignored during idle.

D Moss

Im not talking about reading the O2 sensors. or what the O2's are doing, they are worthless.

What Im talking about is the PCM's TARGET air fuel ratio. When the PCM goes into PE mode it ignores the O2 sensors and uses the MAF, Injector size, displacement, etc.... Information to TARGET to 12.5 Air Fuel Ratio. There is a reading on scan tools that have the F BODY specific codes that tells you what the PCM's target AFR is. Altho this has nothing to do with what the real AFR is, just what the PCM is trying to get by way of its sensors. In closed loop mode the target AFR is 14.7 and the PCM uses the O2's, MAF, etc. to maintain a 14.7:1 AFR. When in PE mode the PCM has a RICHER target AFR and I was simply stating that you would have better luck getting the PCM to target 14.7:1 at idle as a STARTING point.

;)

Thanks for the clarity.

D Moss

The best way would be to use an EGT.

BTW just wondering, what do you guys with big cams end up for numbers in the PE table for idle for reference?

Matt.

Not sure how much it's going to help you since every car is going to be different, and that static fuel pressure, injector constant, maf table values, and ve table values are going to affect it.
But on the Joe O. big-cammed car I did this spring, I want to say I'm right around 0 in the idle range and 12 for the entire rpm range to get a 13:1 a/f ratio at wot.
Idle is still a bit stinky, but once the car is road worth again I'm thinking that I'm going to need to pull quite a bit more fuel out to lean it out. Probably somewhere around -10 to -15. I think that should get me around 16:1 at idle. Only thing is the wideband isn't helping me much at idle. I might need to use an EGT gauge...I just need to find out what temp range I should shoot for.

Hmm.. I"m thinking of pulling -19 or so at idle since PE is just that, by putting in "0" you are adding 16 points to the 128 setting, this is because in your PE vs. TEMP field you have the thing adding 16 points, this is 16 points ontop of your closed loop parameters say being 128, so to get 128 blm & not have the PCM add anything past 128 blm you need to set idle at -16 in the pe vs.rpm range to not add anything. I have the big Joe O' cam in my car & in open loop at idle I have the o2's reading NOTHING as in "4" for o2 readings LOL & I have a laser temp reader & my primaries are showing around 110-130* C which is not too hot at all so go figure, at this point the o2's are thinking the car is completely turned off LOL & the car idles real smooth so I guess the duration/overlap is throwing A LOT of oxygen because on a stock cammed car if the o2's read 300mv at idle you start to see headers glowing at that point while my cam is reaiding "nothing" at the o2s & the primaries are still only 110-130*C which I think is perfectly cool. Also note that closed throttle timing makes a difference, by running more advance you will run cooler, so if you end up running on the lean side at idle, by upping the timing advance you will cool the primaries off, I noticed that aswell, less timing = hotter primaries.

I think to be on the safe side I'm going to shoot for 100-150mv on the o2's at idle which is about 17:1 A/F at idle with a wideband, the last time I hooked up a wideband to my car it read 18:1 A/F at idle, & I think its cuz the wideband couldn't read anything past 18:1 A/F LOL.

I think a very good way to check would be to put a new spark plug in say cylinder #1, run the car at idle for about 5 mins & take the plug out & see if your running rich/lean, then you'll know what to shoot for on the o2s :) again every cam is different, thats why I was looking for a base figure of what to put into the PE table at idle, I personally put in -19 points, which is taking out 3 points from the 128blm, I'll see what that yields at idle for me.

Also, every car is different because Heck I ended up with -9 almost throught my whole rpm range in the PE table to get 12.6 A/F, but i bet if I put a screened MAF back in that would be too lean.

My highest AFG readings to date were 398 AFG's at WOT & 6300+rpm.

WIDEBAND cant measure at idle, the LM1 unit has the ability to adjust pulse width monitoring but I havent messed with it yet to see if it works for idle. the exhaust pulses are too slow to be correctly monitiored at regular monitoring speeds. EGT is the best way to do get the idle tune down. But even if you run a tad lean on the idle its not going to damage anything.

AS far as timing goes, INCREASING timing will make the car run HOTTER because it has a LEANING effect on the AFR.

DECREASING timing has a RICHENING effect on AFR and therefore the exhaust temps will be lower

No, decreasing timing will make the combustion chamber temps lower but increase header primary temp, trust me, try putting in 0* of advance & see how hot your headers will get, they'll start to glow because now when the exhaust valve opens the cumbstion is not yet over & will continue to burn in your exhaust because you fired the spark plug too late in the event.

Now, as for widebands, if I'm in closed loop & let the o2s do their job my LM1 will read 14.7 at idle, so I'm sure it has no problems reading my exhaust at idle, then again my idle is also at 1000rpm & I have an o2 bung welded after the Y-pipe where the LM1 o2 goes in, & when I run it in open loop & o2s are at 100mv or so then LM1 reads 18:1 A/F so I can go by that.

The other thing, I keep running into these problems if I want to tune idle for PE:

To me it doens't work, reason being is even though my BLM's are locked to 128 for WOT, at idle the STFT still work for some weird reason & they compensate, I can easily tell this because when I come to a stop my o2's will read 100mv for a bit & then all of the sudden they start jumping around again, I can see why because the STFT are correcting event though the LTFT is locked at 128, its easy to see cuz when I come to a stop the injector duty cycle hangs around 1.6 & the o2s at 100mv where I want them, then all of the sudden the o2s start jumping around & the injector duty cycle is back to 2.1 where it would hang out in normal closed loop aswell, & if I lean the PE table out more within a few seconds of comming to a stop the injector duty cycle will come back to 2.1 again, if I returne just normal closed loop & disable PE the injector cycle now no longer goes to 1.6 when I come to a stop & then 2.1 but it just goes to 2.1 right away & stays there, so no matter what, for me in closed loop I still get the darn correction taking place.

The other problem? this one is funny, when I come to a stop, for those few seconds that the injector duty cycle is at 1.6 & the o2s are at 100mv I get a DTC (fuel system lean) & engine light comes on, then injectors go to 2.1 & engine light goes away. My STFT go to 150 at that same time while the LTFT stay at 128.

Matt.

Sorry Bunker, i misunderstood.

As far as the troubles you are having with using PE at idle is the same reason I gave up on it. No matter what I did the darm STFT's still compensated. The LTFTs that were learned while in NON PE mode were effecting the STFT's at idle in PE. OFcourse this could be eliminated by using the BLM locker but even then the STFT's in PE mode still screwed up the idle fueling :(

Yep, ok so far I think the only one that works & this is cuz my friend tried it on his car & I looked at his log but have yet to try on mine, he's using the revision "B" flash & on his log in PE both STFT & LTFT are both locked at 128, I've tried revision C/E with no luck, I need to now try the revision B version but its going to take forever to copy all the F*CKING tables over to the revision B flash & try it, if that does work I don't know then, Open loop is very annoying aswell, my right side runs too rich at parts of cruise compared to my left bank so only closed loop to can get right since the cylinder balance wont' work for someone that only gets a split only a sertain part throttles.

Matt.

in open loop mode how can one side run leaner then the other? both sides of the injector bank all fire the same. This is what I am trying to tell you that going by the stock O2 readings is dead wrong and throwing you on a wild goose chase.

You know what you're probably right, why do you think that is, reversion from the cam at sertain RPMs causing 1 cylinder to run a bit leaner making the one side go wild?

matt.

The cam reversion definatly has something to do with it. I have also heard cracked throttle bades can increase the variance in the O2's as well. But as far an a cylinder running lean due to reversion, this is highly unlikely. In open loop mode, no 02 learning is enabled and if you watch your scan tool you will see both injector banks firing the the same pulswidth. now there are the cylinder balance tables ( you should not touch these without an EGT setup) in LT1_edit that specifies the % change in fuel for each individual cylinder, but the stock amounts not only are not great enough to be detectable but have the same variences on both banks.

If you are seeing opposite O2 readings in OPEN LOOP you could have an exhaust leak somewhere causing this. IT could be a lazy O2 sensor. In open loop mode my left bank O2 goes from about .200mv to .960mv and my right bank goes from .120mv to .940mv and both O2s are brand new. There is a difference , but not a big one but I have learned to not even go by the O2 readings long ago. If you think the numbers on the O2s were good, well think about this. With those O2 readings the car was slightly lean on the wideband at partial throttle ( 15.5:1) and rich as a pig at WOT (11:1). but according to my scan tool and data logs the stock O2s were telling me the cars running great.

Large Cammed cars cannot rely on stock O2 Sensors, they are worthless. I cant see how you could possibly be lean on one cylinder with fuel injection, and I dont see how you could be lean/rich on one BANK in OPEN LOOP mode since all O2 feedback is ignored.

LArged Cam guys, take my advice and get yourself a LM1 wideband kit for $350 and stop chasing your tail with the stock O2s. :) You will thank me later.

except at parts of cruise I get 80 on left side & 900 on the right side, both cylinders firing the same & I have no header leaks at all I don't think, then again maybe the header is cracked somewhere or something I don't know, I switched my injectors from left to right with no difference & tried swapping o2s left to right with no difference, I've had this issue since day one, at other part throttle cruises I get the same readings on both sides, at idle I also get the same reading, its only at sertain map/rpm readings that it will show different & others not, I could be at 1500rpm & at say 60 map & it'll be split like 80/900 & 1500rpm & 70 map it'll be same on both. Both banks are firing the same, I also figured if its a header leak the difference would be varied by rpm, in this case I think its more MAP related then RPM.

Matt.

On a quick side note not to take this off topic....

By no means do I know everything but I have been working on f-bodies for about four years now and I thought I had a pretty good handle on these car until I recently started learning about tuning them(havent even done my first reprogram) and realized I've only scratched the surface when a topic like this one comes along. Just wanted to say thanks to everyone for "learning" the rest of us and sharing your experiences. Its posts like this one that keeps our hobby exciting and thriving

We now continue with your regularly scheduled program...... :D

Interesting new addition guys...

I have the latest $EE version from tunercat...

Now whoever sends me an email with the attached older version i will gladly send you this version to not flood Tunercats email

highlander@cartechpr.com is my email

The interesting thing is:

The new definition has a few NICE additions to it that will help tune this cam:
1) Minimum Keep Alive BLM
2) Maximum Keep Alive BLM (don't know what it does yet, but im sure it helps)

most importantly
3) Minimum integrator value
4) maximum integrator value

It gives us a little bit more control on the BLMs w/o making the pcm go crazy....

5) Closed Loop Idle enable Vehicle Speed...

Cool about the vehicle speed closed loop enable.

& what is BLM integrator value?

Keep alive BLM is just that, its the BLM the PCM will retain in memory & start off from when you start the car in the morning, at 128/160, in the morning the car will start off from 128+ in open loop, so if in closed loop you ran past 128 say 130, it'll remember that the next morning, by lowring the 128 value to 120, it'll start off from 120 & remember everything from 120+. So if you ran at 125blm in closed loop, the next morning it'll remember the 125blm in open loop.

Matt.

BLM integrator is also known as Strim or Short trims in current terminology. The INT's are the fine tune for the Ltrims. The INT/Strim's count towards a richer or leaner fuel trimming from 128 to whatever their min/ max is set to then the Ltrimis decreased/ increased by one. The INTs then goes back to 128 and starts trimming again. The INTs move very quickly and can basically be thought of like a fraction of the BLMs.

I wouldn't alter their Min/ Maxes for any reason that I can think of since they're so small on the scale of fuel trimming.

Hope that makes sense,
-Christian

The one i didn't know is the keep alive... there are quite a few things...like startup tables and such.. didn't know that PCM was that "powerful".

Now, if we had a closed loop BLM idle table or something it would be totally cool.

I still don't see the blm blocker.. so i will add it and send you guys the changes...

Well I explained the keep alive BLM above, but anywho, now we need a closed loop disable MPH or open loop enable mph lol :)

Matt.

I bet its there ;)

So are you getting flooded with emails yet Highlander. I know I emailed you as soon as I saw the post.

Not really.. i thought i was going to get a lot more emails...

TC has been doing obd2 work so... i guess... a little help i can give is not bad.

Not really.. i thought i was going to get a lot more emails...

TC has been doing obd2 work so... i guess... a little help i can give is not bad.


if you look in the new ee$ def file and then look at the calibration help and in the drop down box for the constants tables you will see a table there called "Openloop% change fuel/air ratio at idle" but its not in the table itself its only it the help menu

The table is there...

its one of the important tables there.

The table is there...

its one of the important tables there.


its not i my constant tables nowhere, but all the other new stuff is there.

how far down the costants table is it.

Hey Highlander, did you get my email? I sent it a few hours after your posting.

I sent my current ee.tdf, haven't heard from you. Perhaps a spamblocker blocked the email?

Thanks,
-Christian

Hey Highlander, did you get my email? I sent it a few hours after your posting.

I sent my current ee.tdf, haven't heard from you. Perhaps a spamblocker blocked the email?

Thanks,
-Christian

Hey chris.. I did send you your file very very quickly!!!!!

Email me again.. or post on my forum where you have access and i will put it up there if you wish....

highlander@cartechpr.com

Sorry if I sounded accusatory, not my intention, but after re-reading my post I can see how it would be interpreted that way.

I appreciate you taking the time to help everyone out here. Futhermore if my mail server blocks an email from you then it's certainly not your fault. :^)

I'll send you an email from another address where I can definitely receive files.

Thanks again for you help, Cool looking forum BTW, I appreciate the invite.
-Christian

Hey chris.. I did send you your file very very quickly!!!!!

Email me again.. or post on my forum where you have access and i will put it up there if you wish....

highlander@cartechpr.com
:) :)

Never accusatory comming from you...

FYI.. i just sent that mail twice right now.. to the reply address AND to the address you sent me.. the address you sent me doesn't accept emails...

My forum is very liberal... and we can have attachments and such which is a LOT easier to help people out...

http://www.cartechpr.com/forums/index.php?showtopic=331

Thanks Chris, Got the update, I appreciate it.

I'm researching the Gmail issue now, I might have been inactive for too long.

Thanks again,
-Christian

Ok this sucks ones again, I finally had some time to try out the new features of tunercat IE. Intergrator values (STFT) max/min values, I needed to make the max around 135 with maf table altered for idle & min trim to 120 because at times the PCM pulls too much fuel & big cams running at 14.7 AFR tend to surge, I noticed by richening her up a bit she gets better in open loop, these new intergrator values would allow me to trim in closed loop as in make the PCM trim to say maybe 14.0 instead of 14.7 at cruise, & lean her out at idle cuz of the overlap to make the idle smoother.

Anywho! I tried the stupid integrators & they don't seem to work, I set the min to 120 to start off & the STFT still went to 113 & 108 or whatever they used to before but they seem to not want to stay there for long now so they still go lower then the MIN value but they keep resetting more often. What the heck is this, the min before was 64 & max was 192, I set the min to 120 & max to 130 & they overshoot & undershoot.

I'm kinda pissed off cuz I thought the STFT wouldn't go lower then 120 & higher then 130 on my test.

Is there something else in the PCM that allows the PCM to maybe overshoot those values for a split second or something? like to make slight adjustments that don't last long or something?

Anywho thought i'd share my experiences.

Matt.

Well... it could be that the integrators have an incorrect scale...

but do you see any changes in the max and mins when you change them?

No none, stock they were 64/192 now they are 120/130 just for a test, they still go below & above that, my STFT still hit 108 if they feel like it, what is going on?

Weird.

I really don't know.. i would have to check a bit on it... really.. since i don't have my car, i can't try it out... but will let you know what i find out...

well I mean I check it out & did save the changes, I even set the LTFT to 120/130 just to make sure aswell as the integrators with no luck!

Well hope someone else can chime in.

Matt.

http://www.tunercat.com/pdfs/pcm_$85.pdf

check that out

there are a few parameters that if supported by the LT1 would solve this problem once and for all..

Like the FORCE OPEN LOOP vs TPS and Speed mph?? hehe

Yeah I know I"ve already seen this kind of stuff, makes me so jelous :(, that one is for a 91 - 93 C/K Truck, Van, 5.7L & 7.4L (HD)


NO!!!!!!!!!!

Let me see if i can get some help elsewhere... if i do get the info i will modify the $EE Definition and send it to you, TC and a few others... lets just HOPE!.

Try changing the closed loop variable idle to see if it goes into open loop when you get to idle... hmm...

I don't have that option, are you disassembling the code? If you make changes let me try them out. Thanx so much.

Matt.

ON the constants menu

Closed Loop Idle enable vehicle speed.

Ohh thats nothing, thats just to get into closed loop faster, before if most didn't notice, if your car is warmed up but off & you start the car up, it would take some time to get into closed loop? Well thats cuz there is a timer, but another variable that adds to the timing is vehicle speed, if most didn't notice, if you move your car it gets into closed loop faster then if you seat there & wait, thats all. Once its in though thats it.

Matt.

Ohh thats nothing, thats just to get into closed loop faster, before if most didn't notice, if your car is warmed up but off & you start the car up, it would take some time to get into closed loop? Well thats cuz there is a timer, but another variable that adds to the timing is vehicle speed, if most didn't notice, if you move your car it gets into closed loop faster then if you seat there & wait, thats all. Once its in though thats it.

Matt.


stock setting is .9 mph should you set it to 0 and that way it wouldnt matter if your moving or sitting still right.

What im wondering is that it sets IDLE closed loop... so.. hmm.... i guess its the MPH thresshols for idle BLM cells...

like mentioned, it just speeds up getting into closed loop thats all :(

Matt.

:(.

Any progress in getting short terms to behave in PE idle? I was dorking around this weekend with my CC306 flash and I'm sort of at the same place you guys are. Trims head toward the moon in PE idle and the eyes start burning. I'm running WB's in both sides and watching Datamaster as well. For some reason I always thought learning was totaly disabled while in PE. Oh yea I'm running BLM blocker also. We need a Short term blocker also


Steve

BLM integrator is also known as Strim or Short trims in current terminology. The INT's are the fine tune for the Ltrims. The INT/Strim's count towards a richer or leaner fuel trimming from 128 to whatever their min/ max is set to then the Ltrimis decreased/ increased by one. The INTs then goes back to 128 and starts trimming again. The INTs move very quickly and can basically be thought of like a fraction of the BLMs.

I wouldn't alter their Min/ Maxes for any reason that I can think of since they're so small on the scale of fuel trimming.

Hope that makes sense,
-Christian


My WB and Datamaster tests show that the STFT's are not just small corrections or fractions of a BLM at all. It seems that a 150 STFT increases injector PW by a full 17% just like the math would suggest. IE STFTs are not really "small on the scale of fuel trimming" Anybody else see the same thing?

Steve

Any progress in getting short terms to behave in PE idle? I was dorking around this weekend with my CC306 flash and I'm sort of at the same place you guys are. Trims head toward the moon in PE idle and the eyes start burning. I'm running WB's in both sides and watching Datamaster as well. For some reason I always thought learning was totaly disabled while in PE. Oh yea I'm running BLM blocker also. We need a Short term blocker also


Steve


you can not run wide band o2s on your car, for the computer to use, it wont know what to do with them, you need to put the stockers back in. your pcm has no idea what its doing with those wide band o2s in there.

theres a way to lock your short term but thats not your problem your o2s are

Trims head toward the moon in PE idle

so you have set the car to run in pe mode at idle then.

you have to remember that the o2s are always going to respond, anytime the cars on even on start up. in open loop but the pcm ignores them, just as it does in pe mode they are reading the o2 in the exhaust but they are drop out of the loop and there values are ignored.

Sorry, I must not have been clear in my post. I'm still running stock O2's and feeding the stock NB voltage to the PCM. I am monitoring AFR on both banks via my TE Widebands. I am running a closed loop program, but have the PE RPM Vs TPS table set to force PE at idle RPM. I also have WOT BLM locker in my file as well. The locker is working and holding LTFTs at 128. But, since my MAF calibration file and PE table is set to force a leaner idle than 14.7 AFR according to the the stock O2's, the STFTs head skyward. I am watching all this unfold on my WB's and Datamaster. If I run 17 or 18 AFR at idle on the WBs the rich smell cleans up. As said before, NB and WB readings are really kinda garbage at idle on high overlap cammed cars. Just need to figure out a way to either control the maximum STFTs to about 132 or better yet figure out a way to force OL at idle.

Hope that makes a little more sense

Steve

I've got a question I've been thinking about for a while now. How would a waste spark ignition setup similar to the delteq change the false lean at idle with big cams?

Sorry, I must not have been clear in my post. I'm still running stock O2's and feeding the stock NB voltage to the PCM. I am monitoring AFR on both banks via my TE Widebands. I am running a closed loop program, but have the PE RPM Vs TPS table set to force PE at idle RPM. I also have WOT BLM locker in my file as well. The locker is working and holding LTFTs at 128. But, since my MAF calibration file and PE table is set to force a leaner idle than 14.7 AFR according to the the stock O2's, the STFTs head skyward. I am watching all this unfold on my WB's and Datamaster. If I run 17 or 18 AFR at idle on the WBs the rich smell cleans up. As said before, NB and WB readings are really kinda garbage at idle on high overlap cammed cars. Just need to figure out a way to either control the maximum STFTs to about 132 or better yet figure out a way to force OL at idle.

Hope that makes a little more sense

Steve

unfortunalty PE table mode still allows the use of long term fuel trims which will eventually cause the idle to go way rich again regaurdless of the BLM locker. IF you have a big cam running an open loop tune is your best bet, sicne you have a wideband like I do tuning should be easy. I have a big cam and use open loop mode only, I

THere has got to be a calibration for force open loop...

Ok guys, I had some success today. Thanks Highlander for the latest version of the EE def file. After receiving the def file, I set the STFTs to max out at 132 and fired her up. Ureeka. the STFTs rose quickly to 132 and held there. BLM locker held BLM at 128 and a combination of MAF calibrate and PE fueling table allows me to run about 18 AFR on the wideband. I can make the car PE idle so lean that I start to get surge. The only side affect is that the PCM will throw a engine lean code after a timer times out. This takes about 60 seconds or so of lean idle. When the code is thrown, is jumps to Open loop idle. This does not really pose much of a problem if the MAF table is tuned pretty well. As soon as you blip the throttle and go out of PE, and the code clears and SES light goes away. Seems to work like a charm. Now I need to figure out IAC follower stuff since I'm close to stall when I come to a stop and it takes about 10seconds for IAC system to kick in and bring idle back to my programmed 950. So for me the STFT's in the latest revision of TC EE TDF file seems to work fine.

Steve

i understand now my appoligies

you can limit the short term with tuner cat. you can give them a paramiter say nothing lower than 125 and nothing higher than 135 and you can do the same with long term.

yes you can

ooo, ooo, please, send it to me!!! (tunercat upgrade)

Also, if you don't mind, send me your tunercat file for the cc306 cam also. I know I have to tune it to the car, but this will give me a starting point. I have 2 cars (one cc306, the other GM 847) and these will be my first cars to tune in open loop idle.

God I love this post

D Moss

dmoss69@yahoo.com

I can't just send you the TC latest revision. You'll have to get it from TC. Highlander was kind enough to Email me the files after Emailed him my old EE def file as proof of ownership. Thanks Highlander! Maybe he would do the same for you.

Also,

I'll gladly send you my CC306 file. It runs pretty well in my car, except the IAC follower stuff. That being said, I always issue a disclaimer. Be friggen careful! Every car is different. What works in mine, may run like crap in yours. I take no responsibility for damage or other problems that may be caused by running my file.

Steve

Great!

I'll contact tunercat for the upgrade. He knows that I have purchased his program.

Send me your file at dmoss69@yahoo.com

Thanks

D Moss

Well I just got around to trying this method of idle tuning and I must say it definitely made a difference. I no longer smell of gas when I exit my car BUT sitting in the drive-thru to give it the real test, I noticed there was still a smell but an odd smell. Idle timing is around 26-28 and previous BLMs were in the 135 range so now locked at 128 Im assuming the afr is considerably leaner. so my question is...

Now how can I ensure im not running dangerously lean now that I will be going from open loop.. VE calcs to PE calcs instead of basic closed loop? To be honest there are so many variables Im almost afraid to let it idle for too long. I really dont even know where to begin w/o $$$ instruments like what Christian was talking about.

On a side note I now realize I made a mistake dyno tuning my car because I ran it RIGHT after reflashing the pcm so I cant see any possible way the PE table was being used during the run... damn.

EDIT: after driving around some more I have realized the car definitely idles better... probably just b/c of even fueling. Also, It will pull in 1st gear off idle by itself(no foot on the gas) with less surging than I have ever experienced! Only problem is that it does unfortunately smell pretty rich still. I am aware it will never be like it was back in the stock cam era but i think there is still a lot of room for improvement. Like I said the only problem is that even though closed loop blms were 136ish before... now that the car is locked at 128 in PE mode.. that doesnt mean there is less fuel being supplied. Would it be a good idea to unlock the BLMs in PE mode and then try to aim for a little above 128 before I decide to lock them at 128? For all i know they could bottom out at 108 if i let them.

Well i just tried to turn off the blm blocker but had no luck so i started with a new file and just moved all my changes over to it... still no luck. I cant seem to get cell 16 to move off of 128/128 now. :confused: I thought given enough time there is learning in PE mode however I see absolutely no change going on. what gives? what am i missing here?

BLM locker should lock your LTFT (left & right) at 128 while PE is enabled. STFT's will be controlled by the Tunercat STFT limit settings. STFTs will adjust while in PE. Do you have Datamaster set up to verify that PE is enabled at idle? IMO it's unlikely that you can get too lean at idle and hurt your motor. When you start getting way lean it'll start to surge an you've gone too far. If your PE TPS vs RPM table is set up right, it'll kick out of PE and into normal closed loop learning as soon as you touch the throttle. Then it'll go back into PE if you really stab the throttle. Mine still smells a bit like fuel as well. With large overlap cam thats probably a fact of life. I'm gonna start workling on the timing table to try to get peak vacuum at idle. Then back to the PE (idle) table to go way lean and then add fuel as i watch vacuum.

Good luck guys

Steve

I've got a question I've been thinking about for a while now. How would a waste spark ignition setup similar to the delteq change the false lean at idle with big cams?

Anyone care to comment or do I misunderstand something. Would enough fuel be in the overlap to ignite the extra air

Where's the BLM locker? I have tunnercat.

D Moss

P.S. Oh yeah, I just got the newly updated tunnercat EE file also!

Actually for those wondering I dunno, but leaning out idle in closed loop is now possible with new tunercat, I've been running it for a few month now, I have my idle running leaner, I need to go to a shop and have read my CO to determine if I need to go leaner or richer as CO shouldn't be affected by extra oxygen/fuel comming out, cuz CO is a byproduct of combustion.

Whats funny though now in closed loop when I come to a stop, if I hang around about 1-2 minutes idleing I throw a lean code cuz the o2's are reading lean LOL since my idle is leaned out, then the pcm goes into open loop, but I have my open loop tuned to lean aswell, I have both my closed loop and open loop reading 200mv on the o2's, i think she likes it there, so even when I'm ideling for a while in closed loop and throw a lean code having the PCM go into open loop its still running the same, then as soon as I start moving and press the gas she gets back into closed loop. Works great. I can prolly log it and post it so everyone can see my lean idle in closed loop :) causing the car to be forced into open loop at idle lol.

I'd like to see that log. What are your cam specs if you dont mind sharing? Is it solid or hydraulic? Are you using the VE tables to tune for closed loop?

bunker what did you change in order to make that open loop idle?? PE?

what I did is altered the MAF table first in the idle stages so actualy 9-18 AFGs I brought them down by about 5%, this made the BLMs go to 147 or so kinda like what I did before, but this time I put the BLM block at 140blm and the intergrator value (stft) to 138 because it adds about 2 on its own, so the LTFT and the STFT can't go over 140 and you can see the o2's are reading low while both trims max out at 140, the computer sees its lean and can't compensate and throws lean code and goes to open loop, as soon as you start moving, in 2 seconds it immediately goes to closed loop and the ses light disappears, I'll show you all my scans later today or early tommorow its awesome :)

Is it safe to assume that cams with larger LSA's would suffer less from the false lean at idle?

Bunker,

I have had mine set up exactly the same as yours and it works pretty darned good. You just have to kinda ignore the SES light if you idle too long. Also. make sure that the MAF table is in good shape up in the higher Flow area. Since we're limiting BLM corrections on the top end we want to make sure all BLMs outside the idle area are 128 or below. We don't want lean cruise or WOT.

Steve

No because the reason you lean out between 9-18 AFGS is so you don't run into any WOT issues, you also do this to make sure the BLM within that range is scaled way off so that anything after 18 afg's doesn't get effected by the 140BLM limit, make sure you never hit that before you do it. The SES light yeah you just lear to ignore it who cares, kinda reminds me that its too much traffic and to find another way to get to work LOL.

On mine at cruise anything about 1% throttle already goes past the 18 afg's at anyting about 2k RPM.


Also, yes, the narrower the LSA the more problems with lean idle, same with durration, the more durration the more o2 at idle.


Did you just lean out your whole MAF table? Make sure you only lean out the idle areas depending on cam size say a GM847 I'd have 8-14 AFGS I'd subtract 5% or so and limit BLM, I'd also get the Integrator set where the o2's would show 300mv on an 847 and anything bigger 100-200 I'd say. But until you put her on a gas analyzer you can't tell, I'm going to go to my buddies shop and make sure I'm idling at 1% CO which should be around perfect.

Yes correct. I just reduced the MAF in the idle area (about 12GPS) and let the rest of the table alone. What I was saying is that the rest of the table has to be in good shape ie BLM's 128 or so. If someones running a different table or ported MAF, they have to be sure that "off-idle" areas of the table are good so that they don't accidently peg the BLM at 138 and start to go lean in those areas also. I'll be very interested in your CO tests. Did you start to get surge at idle when you got too lean? I'm idling at about 17:1 AFR on the wideband but as we know, those numbers become a bit meaningless.

Steve

Sorry to dredge this up, but I'm exploring the option (or rather fact) that my car isn't going to closed loop idle.

When you guys are saying "large cam" what would large be?? FYI, I'm running a mid 23X low 24X Joe O cam in a 355, speed density 93 car.

After reading this thread end to end, what was the final outcome?? Did the PE Idle setting work, or was an open loop idle the only way???

When you guys are saying "large cam" what would large be?? FYI, I'm running a mid 23X low 24X Joe O cam in a 355, speed density 93 car.



As for large cams, I believe they are referring to cams in the 24X/25X area. I know my big Joe O. hyd. roller cam is in that area ;)

As for large cams, I believe they are referring to cams in the 24X/25X area. I know my big Joe O. hyd. roller cam is in that area ;)

:eek: And I thought MY Joe O Hydraulic Roller was big.

My CC306 is only a 230/244 on a 112LSA and there's a ton of reversion and smelly idle problems associated with it. So this problem isn't necessarily for the huge cam guys only. At the end of the day, PE idle works. You can lean your idle out as far as you want and not affect a good 14.7 cruise AFR or a 13 WOT AFR. The only downside that I can see is an intermittant Low O2 code being thrown during longer idle periods. Tap the throttle and the code clears right away. All that being said, Going leaner at idle with my CC306 didn't necessarily clean up all of the nasty smells at idle. I think it improved things somewhat but it still doesn't smell like a stocker.

Hope I've helped some,

Steve

I hate to bring an old post up, but im going through this right now, and Im just about done pulling all my hair out. Thanks to TurboZ, I have gotten my STerms limited to about 135, and the LTerms are pegged at 128 at idle due to the IDLE PE. However, when the car is warming up(open loop), the IDLE AF is great. Once it goes into closed loop, it richens up, and stays at about 12.8. This is with -19.1 in the PE vs RPM table. It seems that no matter how much I pull, the AF goes right back. PLEASE SOMEONE HELP ME! im begging...

WOW. I can only read so much. I've skimmed over this some and it appears the best way to lean the idle out some is add some timing and disable closed loop at idle only. I have OBDI and LT1 Edit, can somone summarize how to disable the closed loop at idle only and how to tune it for open loop (or power enrichment ...not sure I understand how PE can be used to tune idle though)? Man, the things you all went through to try to force closed loop to do what you want ....just crazy!

and Bunker, for God's sake ....it's tuning, not "tunning" lol ;)

Well, if anyone can summarize what I need to do I'd greatly appreciate it, the timing is easy but not sure on the closed loop being disabled only at idle ....raise the "minimum map for blm update"? ..shoot I don't know....I'm at work right now, maybe I can use common sense and just figure it out when I'm actually looking at it :o

I just wanted to add that I've tried forcing the computer into open loop at idle in order to be able to manipulate the air-fuel ratio. Well, the end results were pretty good, a smoother idle (due to running it richer) but it burned out my cat converter. If you don't run cats or have to pass emissions, this would be ideal. Otherwise, forget it.

Also I would like to mention that my CC 224/236 blower cam has given me zero problems with emissions or weird smells. I haven't even tuned it yet either, very impressive cam IMO.

I just wanted to add that I've tried forcing the computer into open loop at idle in order to be able to manipulate the air-fuel ratio. Well, the end results were pretty good, a smoother idle (due to running it richer) but it burned out my cat converter. If you don't run cats or have to pass emissions, this would be ideal. Otherwise, forget it.

Also I would like to mention that my CC 224/236 blower cam has given me zero problems with emissions or weird smells. I haven't even tuned it yet either, very impressive cam IMO.

So what you tried was with another cam? (since you said you haven't even tuned the 224/236)

My cam is milder than yours @ 220/226/112+6/.544 w/1.6 and idles rich, but not to the extent of causing any real problems. Should I leave it alone or is it worthwhile to disable the closed loop (still not clear on how to do this on my OBDI LT1-Edit, the more I've read the more I'm lost in a way) at idle only? I think my timing is already bumped at idle, maybe that's why it runs decent. Still, if I could get it a little leaner it would be nice. I have no cat so no worries there.

Actually I tried that trick several years ago (running the engine in open loop at idle). My tuning now is just stock, with the exception of increased idle speed and an adjusted injector constant for the bigger 42 lb injectors.

I would like to eventually get the LM air-fuel meter with the Bosch wide-band 02 sensor to monitor the air-fuel ratio (which is so important on a boosted engine).

guys, any update to this? My car is basically at, where we all left off!!

Hey don't feel bad. I've been messing with the same problem for a year and a half myself. The best solution I have found yet is to max out the BLMs at 128 in the ECM Constants table. That way the motor can pull fuel if it needs to but can't add any more. Like other guys have said, extended idle, like when in traffic, will make the check engine light come on. But it will reset itself when you start driving again. As long as the O2s show the motor doesn't need more fuel above idle then there's no harm in maxing out the BLM value at 128. After all, a carburator can't adjust at all and they work pretty well. I've also got some spark knock which I am trying to get rid of by manipulating the VE tables, that's an ongoing thing. In fact I'm going to load a new program in the car for the ride homefrom work. My cam has 230/236 @112 and I didn't think it would be a problem to tune; wrong! Ya know it's painful, but I have to admit that I'm learning some good stuff from having to play with the programming. My set-up is pretty close to yours so if one of us ever gets it right we should share the file. Good luck.