S15 SR20DET JDM

[bachig24u]

Hi,
Calling for SR Expertise on this one.
I have an SR20DET with a preFP tune in it that has Z32MAF, 740cc injectors (possible upto 1000 I just found out).

Issue is, if run up at cruise, light throttle and very slow TPS movement, AFR's a little on lean side 17's.
as soon as you move throttle quickly, injector ms doubles and appears to stay there, afr hit 10's and engine miss fires.
if you come off throttle and feed in gently, you can reduce miss fire and engine runs a little leaner once again, but move the TPS just a fraction too fast at virtually any speed or gear and same happens, AFR's hit 10's missfire.

We can run car up, to almost any speed but add a little too much load to quick or almost everytime after 6psi, AFR's hit 10's again. the log shows inj ms wind right up real quick and this follow AFR's.

I tried updating to FP version, changed injectors size and to Z32MAF and same happens.
Its like a massive boost leak occurs everytime open throttle too fast.

I see knock DTC consult view, but can't image this causing problem. Then again, i can see negative ign timing values in logs on some TPS movements.

Any idea what could cause this?

Sorry no AFR in logs.

KR
Sime

[Matt]

I'll have to look into this at more detail later. However why were some of these maps changed? Try putting those to factory values and also resolve the knock sensor issue too before continuing (it shouldn't have an effect)

Throttle enrichment tables can be used to adjust for throttle opening enrichment during transients. You can try reducing the Async/Sync temperature factor tables to see if these reduce the overfueling and let me know

[bachig24u]

Yes some of the maps were changed in troubleshooting.
If you grab a stock 91f0f .. same happens.
The mechanic was insistent on tps issue but with dtc on knock being one problem, i just can't understand why the second the throttle movement takes engine outside of closed loop areas that it drops afr down so quickly.

I was hoping I missed a knock enrichment table but after reflashing to FP code knock fuelling is no longer there.
I monitored knock window but it didn't count any knock so assumed it wasn't a cause.

The other thing i noticed was reported ign spark timing was often 5 or 6 degs lower and falling negative at times.

I am making assumption that knock detection is cause of enrichment. Keep u posted. Might get back to it this arvo.

----- update -----
I still don't really have conclusive reason as to why enrichment was so excessive off closed loop.
But sorted it with VQ.. Possible remanufactured MAF??

Knock detection primary cause of issue during sudden throttle motion. New knock sensor more sensitive than factory giving false positives but no knock panel light illumination.

[Matt]

There is no knock count for these ECUs in the software. I haven't figured out the counting routines yet. You will notice it is greyed out

If spark timing is lower than actual, this can be an indication that the ECU 'thinks' there is knock - or if you have a knock fault code then it will pull a set amount of 'limp timing'. See our SR20 knock sensor technical note (Support > Documentation > Technical notes) which covers this in detail

[bachig24u]

yeah , I read the doco, it was for nonFP code but its still fairly relevant.

knock analysis, knock map "K'', and knock retard all modified. issue sorted.

The over fueling I'm fairly sure is a Z32MAF pegging at 5.11v at only 300hp at treads.

we originally though misfire caused from over fuelling, but it was knock instead.
The over fuelling just robbed a few ponies and made engine abit lazy.

all sorted.

Thanks for your assistance on this one.

KR
Sime

[Matt]

No probs. Normally once the MAF pegs, the TP will not increase further (flat line) and then the injection will not rise further. So you would actually get a lean limiting condition when hitting the maximum capacity of the MAF