MS3x Fuel cut when IdlePWM > 38%?
 

Hi

I got a second problem with my MS3x
I tried to find out the max. Idle open Duty for Closed-Loop-Idle and therefore set it to warmup mode and changed the values untill the rpm changed no more.

At least that was the plan.
When setting IdlePWM higher than 38%, rpms start hunting, AFRs going very lean while rpm is falling even though PW and Spark are still there (according to log)

Have I reached the non-linear part of the Idle Valve? Would that explain this behaviour?

I attached a datalog. Everything is fine till I turned up IdlePWM to 40% (326sec in the log)

did you add a flyback diode to 12v on your idle out?

your idle valve should be working between ~25-65%

without it, the valve has an effect range of like 10% from open to closed.

Yes, I did
directly on the Tyco ECU Connector

At Idle I am at about 26%, less does not give me faults but rpm is too low to be usable

CrankingPWM is set to 51%, so it should work fine at those PWM, I guess
But it just doesn't

I'm such a noob
Yesterday night, I found out that when %PWM where above 40, it caused the rpm going uptop 1500-1600 which lowered MAP to about 25kPA (TPS closed)

Those low kPA at idle caused the overrun fuel cutoff to activate very shortly, rpm sank again, rised because of high PWM, then again fuel cutoff, ... and so on and so on

What's strange though is, that the fuelcut-light did not light up and also in the logs it didn't show any PW changes.
I guess thats because I have set it to progressive fuelcut, so only a few Zylinders caused the rpm drop, but PW stayed where they use to be at normal running
But then again, the fuelcut-light still should have come on...

weird. I wouldn't think overrun would activate during CL idle. But I could never get idle to happen anywhere close to 25kPa, even at that RPM.

I had my overrun set to 28kPa, IIRC, and I typically idled at 31-33kPa. So overrun would only activate if I surpassed my typically idle load and it'd return fuel before that point for a smooth transition to idle without dips.

I set it back to warmup mode to try out the different IdlePWM's (recognized to late that there is a test mode for such things :facepalm:)
I set fuel overrun to activate above 1500rpm and below 30kPa or so, can't remember

Normally the rpms are never that high (or kPa that low) with closed throttle, so it was an uncommon situation, but still...
Maybe I will change back the settings where they were to find out why the light did not come on.

But first I have to eliminate those nasty sync losses :vash:

I'd just completely disable overrun and try to same again to really rule it out.

Yeah, I already did that and it worked fine then.
My IdlePWM range is 22%-70%, so everything fine

I then turned overrun-cutoff back on and changed it to only come on above 22kPa.
Bingo, IdlePWM still can be set to 50% or whatever without getting those rpm fluctuations.

Now that I know that was the problem, I switched overrun fuelcutoff on again and set it back to 28kPa, because in reality I won't get those high rpms at idle anyways