pcmhacking.net

Before anyone attacks me.
I know gm spent millions getting cold starts right etc.
And i have searched the forum and cant find much info
I know car has to be richer when cold and taper of at around 50 60c coolant temp but i want to try lean of the cold starts once started as i do lot of short trips (from stone cold) to try get bit better fuel economy
Like does it only use these tables below.
Can anyone explain these tables below to me?
My car is idling richer (measured with wideband) when cold
than what the 2 a/f ratio tables below in picture show.
I have (once car is warmed up) my cruise and idle mixtures set up pretty well in open loop hovers around 14.5 to 14.7 afr

In the crank settings circled in red do lower numbers in these cells mean less fuel injected on crank to start up?

Also is there a table in 11p for Intake manifold temp / timing retarding when the intake temp gets to a certain deg c it will pull out a certain amount of timing ?

For the ecotec/L67 (using the factory MAF based tunes) the PCM will go into closed loop mode once the ECT reaches 30° C IIRC.

I've not looked closely at the 11/12P closed loop parameters but this is where I would be looking to get the tune closer to how it was run from the factory.

Sorry I didn't reply to your PM about this, had a bit of a busy weekend.

Is there an actual problem with the way it starts up or just looking for a bit better economy?

No worries vx L67 getrag
Runs starts drives great
Just looking for better economy as is my daily driver

Immortality if it goes into closed loop at 30deg c coolant temp that would be good in 11p.

vp304 wrote:No worries vx L67 getrag
Runs starts drives great
Just looking for better economy as is my daily driver

Immortality if it goes into closed loop at 30deg c coolant temp that would be good in 11p.

I'm not sure TBH, it's something you would need to experiment with. The later style PCM was much more focussed on fuel economy and getting into closed loop mode sooner for that purpose.

The problem you have is trying to save a pittance during warmup which is really in the first 5 minutes. I would be looking at broadening the lean cruise area.

Thanks for the info immortality.

Just had a look 11p has it go to closed loop idle once 44deg c coolant temp
And closed loop for rest of the time once coolant temp is 30 deg c

Yeah in vr they didnt have to worry 2 much about fuel economy but by time vt come was 150kg heavier car and a lot more competition from other car makers.
So they had to try get the best fuel economy they could get.

Charlescrown most of my drives trips are 5 min 5km trips etc mostly short runs