We are having a strange commanded afr issue on my buddy's car. We did some logging and tuning via LTFT last night.
Car - 2005 sunfire automatic
Mods - LE5 intake manifold, K&N cold air intake, magnaflow cat back, autotrans interceptor.
That's it as far as performance as far as I know.
The issue occurred with the stock tune as well as with two subsequent flashes.
The commanded afr immediately drops to 12.9:1 if he goes full throttle from a dead stop and stays there until he lets off. It will also do it in park if he floors the throttle and lets off. If he floors it from a roll, it does drop the AFR CMD. If he rolls into full throttle from a dead stop, it does not drop the AFR CMD The fuel trims are locked when this happens (open loop). It happens whether the interceptor is on/off.
We did NOT change any of the PE engagement or commanded AFR settings because he does not have a wide band yet. We changed the high and low RPM VE tables based on the LTFTs we saw in the first log, and smoothed/tweaked the timing tables.
Is this an automatic transmission thing? The immedate fuel seems to bog the car at low RPMs and it would be nice to tune it out. We tried disabling abuse mode and that did not correct the problem. Suggestions?
It has nothing to do with it being an auto or manual... This is simply due to the lack of tables and commanded stoich. Myself and a few other tuners feel it is somewhat related to the PE commanded ECT values and their modifiers, but when testing this for factual data, the data is never consistant enough to prove this theory... It may have something to d with COT also, but as you know, lack of tables to look at to verify.. I was going to over this in the "How To" I am making, but I will give you some food for thought now... These are the only cars I have ever had to do this on, but sometimes I litterally have to tune the driveability in closed loop. Its not the best approach, and in fact I hate doing it this way, but when you are getting a commanded AFR of 12.2-13.2, what other choice do you have..... I b!tched and moaned to HPT about this, but you know what answer I got from them... I would love to have access to the Stoich table, and ECT/IAT modifers for fueling...
P&P Tuning
420.5whp / 359.8wtq
Not what i wanted to hear, but I had a feeling the answer would be along those lines. In all the logs i've seen though, this is a strange occurrence. It doesn't happen if you roll on and then immediately floor it, just if you floor it quickly from 0% tps to 100% tps. P, N, D doesn't matter.
x2 on ECT/IAT modifiers for fueling, but this seems to be a closed loop -> open loop thing based on delta TPS.
If it's not an automatic thing, i see no way to tune around it. Simply a matter of a missing table.
I'll be damned! It WAS going into PE mode - we adjusted the multi vs RPM table to stoich in the low rpm cells, and tapered it down to a mulitplier of 1 and it affected this off the line enrichment event. It now stays stoich until 2800rpm! WTF is GM doing here?
oldskool wrote:I'll be damned! It WAS going into PE mode - we adjusted the multi vs RPM table to stoich in the low rpm cells, and tapered it down to a mulitplier of 1 and it affected this off the line enrichment event. It now stays stoich until 2800rpm! WTF is GM doing here?
No idea, but don't get me started.... Keep an eye on it Ryan... Like I said above, this is my theory, but after looking at many logs, its just not 100% consistant to prove this...
P&P Tuning
420.5whp / 359.8wtq
Good Find! I think I could use that information to supplement my boost onset tune.
heavyclutch wrote:Good Find! I think I could use that information to supplement my boost onset tune.
just be careful. QWK may have seen more of this occurrence, but this is the first time i've seen it. It only happens right off the line - goes immediately to PE. If you're rolling, the delay tables/values still apply
oldskool wrote:heavyclutch wrote:Good Find! I think I could use that information to supplement my boost onset tune.
just be careful. QWK may have seen more of this occurrence, but this is the first time i've seen it. It only happens right off the line - goes immediately to PE. If you're rolling, the delay tables/values still apply
Forgot to mention, log a status bit on PE and close loop enabled.... You will see what I mean by the inaccurate data.....
P&P Tuning
420.5whp / 359.8wtq
QWK LN2 (needs an @ss whoopin) wrote:oldskool wrote:heavyclutch wrote:Good Find! I think I could use that information to supplement my boost onset tune.
just be careful. QWK may have seen more of this occurrence, but this is the first time i've seen it. It only happens right off the line - goes immediately to PE. If you're rolling, the delay tables/values still apply
Forgot to mention, log a status bit on PE and close loop enabled.... You will see what I mean by the inaccurate data.....
I just meant using the fuel multiplier vs. rpm to help more quickly add fuel in that region of onset where knock retard likes to appear.
What's a "status bit" ?
