Granularity of throttle control

[gnutz2]

I use ignition to control my idle and had the exact same problem as you, like many people have noted, and yourself, the granularity or on/off effect is the ignition jumping from a very small amount up to a large amount exactly when the ignition control turns off and starts running in the main map.

First thing I did was to turn off closed loop idle control, I did this because with small throttle movements (but still within 2%, idle control on) the revs would start to rise but the idle control has other ideas and pulls all the timing it can because its in closed loop and wants the revs to drop, but when the throttle is pressed a little more or the revs rise above the idle switch off point there is a big jump onto the main map which could me 20-30-40 deg btdc.

For the reason above I use the 20x14 table for idle ignition values, this allows me to gradually bring the timing back in by a few degrees (maybe 10-15) at the bottom of the table just before idle would switch off, this makes for a smoother transition onto the main map

Another way to stop this big jump is by reducing the ignition numbers in the main map just above where the idle turns off (typically1-2% throttle and 1500-200rpm), this makes a smoother transition onto the main map.

HTH Baz

[rjwooll]

Thanks - interesting.

However I think if I set it up correctly, there will be little correction to the idle speed at normal idle. When stationary in drive, the ignition would tend to advance to increase revs to compensate for the load on the engine. (Hang on, thinking aloud, why don't I set the idle speed with the butterfly to 850rpm at hot idle in drive, and allow the ignition control to correct idle in neutral/park?) Therefore I'm hopeful that there won't be the kind of jump to main map timings that you and I have both experienced.

Needs some experimentation! I'm happier now about adjusting the butterfly, as the fuel and ignition settings don't vary hugely between 0% and 2% throttle. I can use the narrowband lambda reading to help correct any fuelling deficiencies at idle.

Richard

[ignitionautosport]

Correct, ideally it should be close to the values already in your ignition map at those points, but the wide range it needs to operate under may have made that difficult.

I've used it before and it worked awesome, but was on a manual where no load was ever present at idle position.