EFI University

[AndrisV]

I have a problem with one particular engine, standstill, idle rpm, if I sharply kick throttle wide open, it does rev up with a slight detonation at the beginning. Idle ign. 8-10deg., half load nearby rpm/load about 12-15 degrees, 1000-1500 rpm/ high load - around 5. Alltogether - nothing fancy at all. I could decrease ignition even more, but then again, driveability suffers. Apart from fooling around with throttle, everything is as it should be.

My ECU has an igniton advance (or retard if req.) 2D curve for fast throttle movements facility (works like accel pump), usually I use zeros allover, here, I even got to extremes from 0 to -3 degrees in fastest throttle movement state. Feels and "hears" about same. Maybe I should try to extend that to 5, but I don't see any reason to do that.

It is a NA streetcar with quite high CR (11:1) and very heavy flywheel + narrow OEM cams. So I figure, maybe it's ignition increase rate to blame?

I can change that, at the moment it's set at 0.6 degrees per rev. for advance and 12 degrees per rev. for retard. I have not seen a lot of management systems, that even allows to change this, maybe someone could shed a light, what is common figures for this? Especially on OEM managements...

[Johnny_9]

i think u need tip in retard and increased rate of change

[AndrisV]

Naah, I will sort that one out with more tip in retard as I said, I already have that in place.

This situation just got me thinking about ignition angle increse speed per revolution and what is general rule of the thumb for that.