xhomm02

Hi, I noticed an interesting thing:

In my stock maps idle ignition advance is 10 degrees. With this I run 750 RPM idling and, +-0 LTFT and 2,03 ms fuel injection.

When I modified them to 15 degrees ingnition advance, I am still running smooth 750 RPM, but injection time DECREASED to 1,79 ms and LTFT jumped to + 10% !!!!

It means that with increasing timing we can get much more fuel efficient idle, but can anyone explain the +10% LTFT????

Golden

iTrader: (1)

The 10% ltft explains the leaner IPW.

I think the real question is, "What caused the LTFT to go up to 10%?" Is it because of the increased Timing? Or something else?

xhomm02

I do not think so. AFR in close loop must be the same, so it is not leaner. But shorter IPW (with increased timing) is sufficient for stable idle while maintaining AFR.

If the common IPS was 2ms (with 0 fuel trims), when it decreases to 1,8ms, LTFT should be negative 10%, not positive, or am I missing something?

The only thing that I changed is the idle timing (0-30 load, 0-1000 rpm cells)

fostytou

iTrader: (15)

Is it possible that is the closest it can get with the smallest increment it can use to adjust? Maybe with that amount of timing its just tossing up between the two values.

Isn't there an IPW resolution patch? I can't remember if it just allows lower pulse width or higher resolution of pulse, but that could help you out.

In any case, I say if it runs right screw it. If you really wanted to try to get the LTFT in check you could adjust MAF Comp, but that isn't ideal if that is set properly.

xhomm02

I am afraid there is no patch for Cobb ATR :-).

It keeps the lower and value of IPW (in a different map there i can see IPW jumping from 1,8 to 2 ms all the time, but in this case the lower value is kept permanently)

I just wanted to try the higher idle timing like in 2011 maps and I got really surprised with the much lower IPW. I will keep it, as low LTFT does not influence anything during common driving.