Help with IAT issues in SD, Open Loop

[Draco]

Hi guys,

I've bitched in a couple of other threads about this problem and still havent found a way to solve it on my own. I have an 00 C5 M6, running a v3 OS (02030003) Cal version 7.76. I am running in open loop and Mafless, and my IAT sensor is working just fine. The C5 intake sits in the engine bay, so when my car sits at idle in traffic, the temps climb.

I have my VE table dialed in using a wideband for approx 30* IAT. Idling and cruising around near this temp and my commanded AFR matches the actual AFR perfectly. My problem is that as IATs rise, my mixture leans out compared to my commanded AFR. This makes perfect sense, but I need to find a way to correct for this. Right now all I can do is tune my VE to a warmer IAT, but then it goes RICH at lower IATs. I have tried different values in the Open Loop IAT multiplier table (A0014), even maxing out the 50*+ cells to 1.30 and these appeared to have absolutely no effect? I have also tried different blending values (B4901) and even turned the blending off entirely and this didnt help.

I read in somewhere in another thread that the PCM is dumb to the IAT in SD mode. I thought SD mode by definition relied on IAT, MAP, and VE to determine the airflow? How can a PCM calculate the airflow accurately without properly considering the incoming air temperature???

Anyhow, I will keep fiddling around with the aforementioned tables but would really appreciate some guidance. I'm so confused about why I can make huge changes to the A0014 and B4901 tables with zero difference in either direction.

Thanks for any help! :master:

Craig

[Tordne]

Looks like you are looking in the correct area in the B0014 table. I am surprised that you say that this has "no effect" even when maxing the table out to 1.3 multiplier :Eyecrazy:. I have (when previous experimenting) found that this definitely works....

So a couple of questions for you:

1) You are 100% certain that you are running in SD mode and not from MAF (assuming it has not been physically removed). Can you verify in the Scan Tool -> F7 (OBD II) tab, in the DTC Summary section that the P010x DTC code is set and that you are in SD?
2) You say you are running Open Loop, but what AFR are you commanding in the B3647 table (assuming that is in that Custom OS)? If you are commanding 14.63 you are in fact in Semi Open-Loop and fuel trimming will be occurring.

A number of guys are using this successfully so we should be able to add you to the list.

Cheers,

[GMPX]

Craig, can you please do me a favour.
Tell me the Checksum value of the Operating System segment.
Early Custom O.S #3 files did not have that table in the code.

Early O.S V3 = $CB59
New O.S V3 = $91D1

Cheers,
Ross

[Draco]

Craig, can you please do me a favour.
Tell me the Checksum value of the Operating System segment.
Early Custom O.S #3 files did not have that table in the code.

Early O.S V3 = $CB59
New O.S V3 = $91D1

Cheers,
Ross

my checksum is neither lol. its $429E.

Did I screw up choosing/flashing my custom OS?

My commanded AFR varies based on RPM and MAP. Scales down fairly linearly from 15.5 at idle, to 15 at cruise, to 12.8 at WOT. My MAF is disconnected and physically removed. I have turned off the MIL but not the actual DTCs.

THanks for the help so far guys! I'm going to log some high IATs, and do some hand calcs on the grams/cyl to compare with the PCMs grams/cyl to see if the IAT multipliers are being used.

[GMPX]

O.K, so that is strange!.
If you want to Email your file to me - ross at efilive dot com, I'll make sure you have the correct O.S.

Cheers,
Ross

[Draco]

Thanks for the great support Ross! It appears that the IAT multiplier is working now, just need to dial it in.

Cheers!

Craig

[BowlingSS]

Thanks for the great support Ross! It appears that the IAT multiplier is working now, just need to dial it in.

Cheers!
Craig

So what was your problem Craig?

Bill
:cheers: