Car is a 2002 with an fm2 turbo kit, mspnp-pro, and flowforce injectors.

The problem I am having is when I come to idle from say 4000 rpm with the ac on the car never catches itself it just plummets from 4000 rpm to 0, on the off-chance it does catch it catches at around 500 rpm and then closed loop idle kicks in and brings it up, I have attached my current tune and a data-log of this happening, the examples is at then end of the log starting around T=25s.

From what I see my car sets the idle valve to the given value from the initial value table as rpms fall (this is the correct value, I have verified) and the idle still plummets, I do notice that the afrs stay stuck at 18 why is the car not spraying fuel? This must be the problem since it has the proper air entering from the idle valve? Thanks for your help, I've tried my best, there must be something I am missing.

 

I can't look at your tune right now on this PC, but have recently had a similar issue, didn't happen when cold, only after driving for some time when the car was hot.

I solved it by double checking my CLI Initial Values table, and added an extra row for 90*C CLT (I know I should switch to AIT... I'm working on it!), and I increased my Fan Idle Up%. To find my Idle up I simply made the fan turn off and on to see what the difference in Idle PMW% was, then bumped the value.

Maybe you've got all of that sorted, but that's what helped me. Oh, and make sure your VE cells in and around idle and the overrun approach into idle are delivering a decent AFR.

 

Its not my initial values, I have those all sorted well and am using MAT for them so It should be fine even when hot. I think it must be something with my afrs according to the log, but i'm not sure.

 

Here is another datalog of it happening a few times, I tried increasing fuel but no matter what the afr coming from 4000 rpm clutch in to idle is always pegged at 18, could my wide band sensor be going out, or is the engine not moving enough air to give a reading? Very frustrating.

 

A few things:
- Why use MAT? Idle seems to depend more on coolant temp than MAT
- Why don't you have MATs below 100 degrees? Sometimes the air may be colder
- Your AFRs are running away from you, going all lean. This is presumably why the engine stalls
- Your idle valve shift value is closed above 1500rpm. Mine is closed above 5000rpm. Not sure if that has something to do with it, but I suspect it may. Increase that to 5000 and see what happens.
- Are you corresponding VE cells tuned properly?
- When the rpms drop, your idle valve opens to more than 50%, even though your initial value should be 30ish. So the CL is already trying to fight the drop in rpms. No idea why this is happening.
- Your closed loop sensitivity of 3250 seems fairly aggressive to me. Same with your proportinal gain. How were these values tuned?

 

1. I use MAT because that is where I saw real differences, when I used coolant I could be at 200* F but my mat could be anywhere from 100-160 at the same coolant temp so I used mat because it seemed to be the setting that mattered.

2. No MAT's below 100 degrees because the values at 100 degrees are nearly the same as the values for anything colder so I didn't see the need to use and table resolution there.

3. I agree that the AFR's are the problem but I I dont think its my ve table values I think for some reason it may not be spraying fuel there, even though I have overrun fuel cut off.

4. That actually makes sense because in the data log I always wondered why my idle valve didn't open to my initial value until around 1500, I will change this and see.

5. My ve table is tuned using veal and idle ve table by hand, if anything they are a little rich, but consistent.

6. I tuned the pid settings according to the manual, increasing I- value until I can meet my target, increasing P- until oscillations occur, D- to soften both of them, and increasing sensitivity slider for reaction time. I was just testing sensitivity there, I set it back to around 1000 now however I found even with sensitivity that high I didn't get oscillations but I dont think it was doing me any good so I set it lower again.

 

It turned out to be the shift settings, thanks for catching that. The car drives and idles like stock now. Crazy how one little thing can cause so many headaches.

 

I set mine to "0" (no closing) a long time ago. Everything works better, and I could not tell what it was accomplishing anyway.