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.

 

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/Ana...OT_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.

 

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

 

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.