Feature request: ignition advance rate of change limiter

[sd1nl]

Here's something that might be useful for car engines aswell as motorbikes:

When you go from an overrun situation to drive and you hit the throttle too fast you sometimes get a nasty jerk. The ignition advance in these situations goes from slightly retarded to fairly advanced very fast, resulting in an unpleasant torque jump.

Solution might be to limit the rate of change of ignition advance.

I remember Rover did more or less the same thing in their 3.9 v8 engines by fitting a kind of dashpot like device in the vacuum line to the distributor. This dashpot device worked only one way: limiting advance rate, but not the retard rate.

VEMS seems to have ghe same feauture: http://www.vems.hu/wiki/index.php?page= ... unAndTipIn

Maybe something to think about.

[dontz125]

Not sure which version of MS3 you're running, but the current code allows progressive spark return over some settable number of seconds.

[sd1nl]

Not sure which version of MS3 you're running, but the current code allows progressive spark return over some settable number of seconds.

My version only supports gradual spark change when entering fuel cut.

What I mean is a limiter to the rate of change of the spark advance. This mainy applies when hitting the throttle upon returning to drive after fuel cut.

I use pre1.4beta15. Did anything change?

[nathaninwa]

For some reason I think it's there too. I'll look when I get home but your firmware should have it. I remember testing it in my manual car to stop the gear box noise on the tip in trantion from fuel cut

[sd1nl]

I think there is only a spark advance transition when the fuel returns at low rpm when coasting. As soon as you hit the throttle the advance goes to the value commanded bij the spark table immediately.

Would be nice to make the advance change-rate smoother. Doesn't really matter if you come from a fuel cut or if you are coasting with the fuel on.

[nathaninwa]

I see where the problem lies. There is a timed from decel to full advance that is user adjustable, but if you read the ? It says the timed limit is ignored of tps gos above the set threshold

Try playing with the tps engagement and let rpm and map have more control. I like the bypass as I can get into boost quickly and like that feature versus waiting for the timing to come in

[sd1nl]

Try playing with the tps engagement and let rpm and map have more control. I like the bypass as I can get into boost quickly and like that feature versus waiting for the timing to come in

Not much to play with the tps engagement, you really ought to set the treshold as low as possible, or there will be a massive jerk when touching the throttle after overrun fuel cut.

[Boshnakov]

Am I missing something but why not just change your ignition table in the lower regions? Simple as that. My car also had this jump after fuel cut, but as soon as I changed the table it went good.


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[sd1nl]

Am I missing something but why not just change your ignition table in the lower regions? Simple as that. My car also had this jump after fuel cut, but as soon as I changed the table it went good.


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You got me thinking here. I tried today to "bake" a transition from high to lower advance in de table, by advancing more on overrun.

The result is not bad.

[suberimakuri]

So at like 15 or 20kpa you reduced timing from 30 something to a lower number? Or the reverse?
Can't say I've noticed an issue but curious.

[sd1nl]

Overrun is now at close to 48 at 3000rpm, and 30 ish at 1500, but retarding quickly as map load goes up. Drives quite smooth. Less engine braking though, but I don't mind.

[Boshnakov]

You could also change the Decel Fuel Amount setting. Make sure that Accel TPSdot Threshold is not too big.


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