I posted a few times in another thread so you may want to read it first. http://web.camaross.com/forums/showt...hreadid=238625


Reloaded my laptop with win2k today, xp kept crashing with my belkin usb to serial adapter including once in windows while programming my PCM, lesson learned, always program from dos if at all possible. I have a pc set up in my garage with a flat panel monitor in which I replaced the CCFL's "bulbs" and the inverter "only $90.00 for a $300.00 monitor". Very easy process I will gladly share if anyone has a flat panel that the screen won't turn on. I use it now with a dos boot disk to program my car with and the laptop to run datamaster.


After the car is warm it's getting a map reading of 57 to 62 at idle in park @1000rpm, and 72 to 77 at idle in drive @850rpm. Does this seem a little high to anyone or am I about right on these readings. I can't run the car in closed loop or it will start to stumble/backfire and return itself to open loop. I may need new O2's as they seem to stick sometimes on a reading for a couple of recording cycles in datamaster, not sure if this is normal/abnormal.


The car seems to make more power as soon as the timing advance reaches above 40 degrees, without any extra throttle advancement its a noticeable jolt, at part throttle. The motor has about 2k miles on the rebuild. I've always read that you don't need more than the stock timing on these cars since GM has them programmed pretty close to perfect. I have added around 2-3 degrees across the board so far and more to the lower rpms to try and make the idle better and low rpm driveability.

 

with the CC306 cam you definatly need more spark advance.

Before I offer any advice, Are you running a Ported MAF or a Stock MAF ?

 

It's the stock MAF with the screen removed, already read about all the pitfalls of porting your MAF.

 

In my opinion you need to increase the low RPM timing advance more that 2-3 degrees. and the closed throttle timing advance needs to be higher aswell.

Have you changed the INJECTOR CONSTANT to match your new injectors? IF its still set to the factory rating your killing your motor with way too much gas.


it seems like in OPEN LOOP mode when the PCM is ignoring the O2 sensors its ok. but once it goes into closed loop mode and makes correction from the O2 readings is when it goes astray.
This doesnt neccessarily mean the O2s are bad, but it is possible. I would put new ones in anyway. this may be an issue, buit also I would change the CLOSED THROTTLE spark advance to about 35 degrees at idle as well.


code 33 on a VIN P 94 5.7L means =
MAP sensor signal voltage was too high (low vacuum) for 1 second when throttle opening was under 20% and engine speed was above 1250 RPM.

This doesnt neccessarily mean there is an issue with your map sensor. I have a larger cam than you and less vacuum than you and never got this code. Its probably just a code that poping up because of the problem your having, not something thats causing the problem.

If u could send me a copy of your tune, email it to tripintaz@tripintaz.com I could take a look at it for you. see if i ould recomend anything to you

 

Well looking at the timing seems good at lower RPMS and closed throttle, altho 41 degrees of advance at WOT above 4000 rpms is a bit much in my opinion. Im glad that the timing increase helped.

Does it still sputter and stumble in closed loop ?

 

I changed the injector constant to 31.68 when I put them in. Changed the timing tables to what I read in some of your earlier posts about the subject and it made quite a bit of a difference. I seen a little bit of knock before the car was at normal operating temps but once it was warm I recorded no knock at all after 3 WOT passes "glad I live on the edge of town". The car surges at idle when its cold and this was happening previously also but once it gets warm it idles better than it ever has 57-60 MAP@1000rpm and it even sounds better too.

Overall the car seems to have a little more throttle response and it runs much stronger at WOT, of course I need to get it to the dyno soon and do some fine tuning there. I will play around with the timing tables some more to see where my limits are and I'll update this post when I figure that out. Thanks for the help tripintaz, its much appreciated.

 

Damn that was a fast response on that email


I'm programming that tune as we speak, the advance above 4000rpms was set to 38 degrees and I sent you my revised version. The only things I changed were the 95-100 MAP, so you are looking at the almost original tune on my previous data logging run.

EDIT: I haven't tried it in closed loop yet, I'll also update when I do that.

 

I run a completely OPEN LOOP tune. My cam is too extreme for closed loop operation. Joe Overton Told me this personally and suggested an aftermarket PCM. But he said a OPEN LOOP tune on a factory PCM would be ok if I was willing to sacrafice some HP.

the CC306 cam isnt too extreme for closed loop, but why it goes nuts when it goes into closed loop is strange. Are your MAF tables modified? I run stock MAF tables, I tried to lower them by up to 18% to lean out the idle and all it did was make the car want to stall at any low RPMs. YOu may have the MAF tables too low. Try the stock tables in closed loop mode. What I actually did was change my injector voltage offsets which made it leaner at an idle but didnt make it stall out by changing the MAF. In my experiences with tuning adjusting the MAF never gave me good results. Which I reiterate my 260/260 cam runs stock MAF tables. It is much better to adjust the injector constants and offsets for idle and part throttle tuning.

http://carprogrammer.com/Z28/PCM/Injector/injectors.htm

you might want to try setting your offsets to teh ones on the above table and using stock MAF sensor. and lower your part throttle timing to the lower 40's range and see if that helps it run better in closed loop. If you are still having problems I would have to say I think your O2s are trash and you need new ones. Infact I persoanlly would and DID use brand new O2s with a new engine.

 

My MAF calibration tables are stock, I take it you mean my AFR x 10, open loop vs. coolant temp vs. map? And how do I translate the numbers from that talbe into tunercat, do I just remove the decimal points and paste the numbers?

EDIT: By saying "that table" I mean the injector constants, don't want to cause any confusion for anyone who may be reading this.

 

the AFRx10 talbe will only change the fuel when in OPEN LOOP mode. what u do is multiply the number times 10. so a value of 1.4 would equal 14.0:1 AFR. Since I run an open loop tune only I use this table to fine tune part throttle driving for my car. If you plan on an a permanant open loop tune then this table will be very helpful. But the Injector OFFSET table should be set right 1st before you change the OPENLOOP AFR table.

injector Constant is the injector size you put in the PCM
injector Offset ( voltage) table is used to control the injector opening times at a certain voltage.

 

If you go to WOT in open loop, does this table completely control the AFR or does the % Enrichment @ WOT table also kick in?

 

Both tables would apply in open loop mode.

 

But how do I translate these #'s into tunercat http://carprogrammer.com/Z28/PCM/Injector/injectors.htm

For instance, tunercat says 305 @0.00 and this table shows 7.00 @0.00, so how do I input this into tunercat. Do I take out the decimals or is this table made for a different tune program as in LT1 edit. So do I input 700 in place of 305? Or am I just thinking too much into this and its much more simple than that.

I've also read that depending on which fuel trim cell you are in it gets calculated into the WOT tables.

 

Does anyone know the answer to this?? I don't want to plug these #'s in without knowing the proper format.

 

sorry, those tables are in the LT1 edit format. You want to move the decimal over 3 spots to the right for tunder cat.