Feature request - electronic overrun valve

[Marek]

I'd quite like to experiment with an overrun valve which can be controlled electronically. When I snap the throttle shut, MAP drops very fast and not all cylinders are able to breathe enough air. What appears to be happening for a short period is that they are robbing each other of air and then engine rpm oscillates slightly.

I'd quite like to have a table or curve where one axis for MAP drop in "A" amount of time and the other axis is seconds (mSec) of time for "B" amount of idle valve opening to momentarily inject some air into the plenum, whenever TPS < "C" (where "C" is probably 1% or lower) but was previously higher than the threshold.

Occasionally, I find that this resonance or shunting or momentary charge robbing happens in specific parts of the map and it'd be nice to have a second feature requested to pulse some air into the plenum if rpm oscillates and exceeds a certain value when TPS is open and am running steady state conditions, i.e. TPSdot is low but rpmdot suddenly isn't following its usual correlation it it.

Again, it seems that running this through an idle valve ought to have the dersired result.

kind regards
Marek

[elaw]

That's interesting!

The OE ECU in my Saab has a feature that I suspect may be to accomplish the same thing. Basically during overrun, the idle valve is held open a bit to prevent MAP from dropping too low. The amount it's open varies with RPM and MAP... I've never been able to figure out if it's open- or closed-loop control.

[DaveEFI]

My very early EFI RV8 had a mechanical valve which opens under high vacuum. Other versions had an electric one. With MS, I've managed to do the same by cutting the fuel on the over-run. Surely that is going to react as quickly as a mechanical valve?

[piledriver]

Keeping the MAP up a bit on decel also reduces sucking oil into the intake/past the rings etc.

I think there's an option to keep the IAC open, I have forgotten how the logic works.