Hunting for Idle - AFM issues?

[kostjazz]

Hi guys,

I'm getting this issue on the video here: https://www.youtube.com/watch?v=1mGYS6f8ZN8

Starting from about 1 minute in the video. It idles somewhat fine. A bit rich but fine, then if you rev it quickly it dies.

I've noticed that when it was idling MAF reading was around 1.1 - 1.2, but after revving (~1:50 in the video) MAF reading was all over the place - 1.5 and even higher when it was about to stall.

Do you think my AFM is cooked?

S15 with sr20DET, 1000cc, z32AFM, Poncams, 3071 high mount.


Also: my BOV plumbing is not ideal, but I guess it shouldn't make it that bad, right(picture attached)?

Fuel pressure seems fine. Question. Is there anything I can check before ordering R35 GTR afm?

[Matt]

Post a screenshot of the log (MAF, TP and injection time) and then we can tell you for sure what is going on

[kostjazz]

Logs and bin files attached.

[kostjazz]

Also one very important piece of info:
Before it started doing so the car has been sitting on stands for about a year. In that time I’ve installed this turbo, exhaust and intake.

Checked for vacuum leaks - didn’t find anything too bad.

[kostjazz]

Also screenshot of the logs of the car dying after quick rev is below

Thanks a lot for your help

[Matt]

Thanks for that. What you can see is the blue (airflow meter) is still reading airflow whilst the red (RPMs) are dropping

Probably your turbo is still spinning and sucking through airflow

This causes your green (injection time) to increase and cause the problem

Normally longer pipe between the turbo and MAF can help with a bend, or putting the MAF in the pipe on the boost side

However there is new firmware FP1.1/FP2.1 has an antistall TP limit table, in there to now reduce the impact of this

It is not available for S15 just yet, but I've started updating the patch code this week to cover the SR20DE/SR20DET models so should have that available soon. Will require a board remove + reflash

[kostjazz]

Thanks for the explanation Matt.

Would you consider it normal for AFR to lean out as the result of it?

[Matt]

No. That part is strange

Light purple (injection time) shows it adding a ton more fuel after its initial decel fuel cut (downto about 2000rpm)

The dark purple (AFR) shows it totally going lean even when that injection time is adding a bunch more fuel. Either it is not reading properly (turbulence or otherwise), or something else weird going on there. What does the narrowband O2 sensor show?

[kostjazz]

Looks like My Wideband is really laggy comparing to narrow band

It actually gets really rich before stalling.

[kostjazz]

Ok, quick update.

It was indeed my intake. Just tried to make it longer and the problem went away

[Matt]

Good work. Yeah we could see narrowband read rich as you said firstly before wideband. The bends in the pipe help with stopping continous suck through of airflow