E38 idle tuning

[Tre-Cool]

Nice update Joel.

I have the idle pretty well nailed in my own car, so i'll have a play around.

I had been setting the 1703 & 1704 to match the non dtc codes values for a while.

What I have found strange & makes me wonder how the min airflow values are truly calculated out/from. As different OS cals use different B1602 (Airflow Correction Coolant Multiplier) values along with under/over correction multipliers.

Example: Logging Dynair ecu says 14g/sec for 800rpm idle

so enter in 14 into the 800 rpm column, if the multiplier for 92c is .29 is the actual min value still 14 or lower? I think it's a lower value as I've found that if i change the multiplier to 1 the car will idle really high and want to pull timing out to get idle rpm down.

Put it back to the lower multiplier and it's bang on again for blade position and spark timing.

[hymey]

Nice update Joel.

I have the idle pretty well nailed in my own car, so i'll have a play around.

I had been setting the 1703 & 1704 to match the non dtc codes values for a while.

What I have found strange & makes me wonder how the min airflow values are truly calculated out/from. As different OS cals use different B1602 (Airflow Correction Coolant Multiplier) values along with under/over correction multipliers.

Example: Logging Dynair ecu says 14g/sec for 800rpm idle

so enter in 14 into the 800 rpm column, if the multiplier for 92c is .29 is the actual min value still 14 or lower? I think it's a lower value as I've found that if i change the multiplier to 1 the car will idle really high and want to pull timing out to get idle rpm down.

Put it back to the lower multiplier and it's bang on again for blade position and spark timing.

Trecool , yes I have found that, GMs weird way of doing things, the low value decimal multiplier has to stay.

A good give away is cranking idle air and corresponding TB percentage. Change the cranking idle air and watch the percentage change. Then while idle tuning you may have the limits set tight around 55 / 57 for say and notice you would have a certain idle air value. Take note of the idle airflow logging and also the percentages and then while logging cranking you can see what's happening. I find I usually have say about 1 g/s less in cranking idle air then min idle airflow but I like the PID to trim down a touch rather then up as it stops the idle dropping to fast as you pull up.

I have noticed more the way it works in HP and I can see it all builds from a min value and integrals add to that value.

A good experiment is logging cranking and playing with that then you know what is exactly what.

Once you have it close , with those limits , I find dropping min idle air value only 0.2 make A a big difference in the way the idle settles when you pull up or drive off. It helps a lot with drivability .

I have also seen statements on websites stating it has nothing to do with idle. This is untrue as you found from the multiplier .

The last 3 / 4 cars actually all had varied combos and all ended up the same values. One had a 227 239 114, 2 had small cams and the other was a high comp engine with a 229 240 109 . All had same values.

The trick is keeping those limits close. I've been doing it this way for a while too I just have not been online.

The PID can learn much faster and work better in its correct range.

Regards

Joel