2.2 PE Delay
2.2 PE Delay
I learned something new today with my FIC. After installing my wideband, i had thought that the stock PE delay on the cobalts gave out after about 4200RPMs where the AFR dropped from 14.5 to about 12.8 (it continued to lower as the RPMs increased all the way to the low 11's at 6500RPMs) Throughout all my full throttle runs, starting at any RPM, the car would stay near stoich until this RPM of 4200RPMs
Anyway, I made a general change to the MAP fuel map to add fuel at all MAP values over 2500RPMs. After doing this, I madew another series of full throttle runs. and the results? AFR dropped to 13.0ish:1 after 3000RPMs This would mean that between 3000RPMs and 4200RPMs, the car is actually not in PE delay, but is instead just tuned from the factory to run 14.5:1 AFRs through this range.
I thought this was an interesting note, and an odd choice by GM to help the cars fuel economy....
while it is still not ideal for boosted applications, this DOES mean that any programs that adjust fuel but cannot change things like PE delay (such as the AEM F/IC, although the FIC can compensate through O2 sensor tuning) will allow your car to run a safe AFR value from 3kRPMs instead of the low 4kRPM range
Anyway, I made a general change to the MAP fuel map to add fuel at all MAP values over 2500RPMs. After doing this, I madew another series of full throttle runs. and the results? AFR dropped to 13.0ish:1 after 3000RPMs This would mean that between 3000RPMs and 4200RPMs, the car is actually not in PE delay, but is instead just tuned from the factory to run 14.5:1 AFRs through this range.
I thought this was an interesting note, and an odd choice by GM to help the cars fuel economy....
while it is still not ideal for boosted applications, this DOES mean that any programs that adjust fuel but cannot change things like PE delay (such as the AEM F/IC, although the FIC can compensate through O2 sensor tuning) will allow your car to run a safe AFR value from 3kRPMs instead of the low 4kRPM range
currently, its not sending a MAF voltage at all, and i also have a MAF voltage CEL, so im unsure whether or not it was wired wrong, or if maybe my MAF sensor is just failing, but that is my only complaint with my whole tuning situation.
my only suggestion is to get it professionally wired.
my only suggestion is to get it professionally wired.
Senior Member
Joined: 03-03-06
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From: Pittsburgh, PA
currently, its not sending a MAF voltage at all, and i also have a MAF voltage CEL, so im unsure whether or not it was wired wrong, or if maybe my MAF sensor is just failing, but that is my only complaint with my whole tuning situation.
my only suggestion is to get it professionally wired.
my only suggestion is to get it professionally wired.
New Member
Joined: 06-01-08
Posts: 3
Likes: 0
From: Columbus, MS
I learned something new today with my FIC. After installing my wideband, i had thought that the stock PE delay on the cobalts gave out after about 4200RPMs where the AFR dropped from 14.5 to about 12.8 (it continued to lower as the RPMs increased all the way to the low 11's at 6500RPMs) Throughout all my full throttle runs, starting at any RPM, the car would stay near stoich until this RPM of 4200RPMs
Anyway, I made a general change to the MAP fuel map to add fuel at all MAP values over 2500RPMs. After doing this, I madew another series of full throttle runs. and the results? AFR dropped to 13.0ish:1 after 3000RPMs This would mean that between 3000RPMs and 4200RPMs, the car is actually not in PE delay, but is instead just tuned from the factory to run 14.5:1 AFRs through this range.
I thought this was an interesting note, and an odd choice by GM to help the cars fuel economy....
while it is still not ideal for boosted applications, this DOES mean that any programs that adjust fuel but cannot change things like PE delay (such as the AEM F/IC, although the FIC can compensate through O2 sensor tuning) will allow your car to run a safe AFR value from 3kRPMs instead of the low 4kRPM range
Anyway, I made a general change to the MAP fuel map to add fuel at all MAP values over 2500RPMs. After doing this, I madew another series of full throttle runs. and the results? AFR dropped to 13.0ish:1 after 3000RPMs This would mean that between 3000RPMs and 4200RPMs, the car is actually not in PE delay, but is instead just tuned from the factory to run 14.5:1 AFRs through this range.
I thought this was an interesting note, and an odd choice by GM to help the cars fuel economy....
while it is still not ideal for boosted applications, this DOES mean that any programs that adjust fuel but cannot change things like PE delay (such as the AEM F/IC, although the FIC can compensate through O2 sensor tuning) will allow your car to run a safe AFR value from 3kRPMs instead of the low 4kRPM range
1. You aren't starting your WOT run until the 3000rpm range where you are still below the PE Delay RPM which results in you seeing a stoich AFR
2. You aren't in PE mode
Another thing to note with the Cobalt is that the PE enrichment rate is on the slow side, which means it's going to not be an instant switch to PE fueling.
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