Tuning issues SR20DET

[Thilo]

Hi,
I've got two major problems with stetting correct lamba/ve.

1) I allways get lean readings from lambda sensor at fully closed throttle, but I allready disabled overrun fuelcut and decel enleanment. Is it just a sensor reading error and why does it do that? Also autotuner allways try to set VE to brutal high values. I just put values in, which seemed more realistic to me.

2) I allways get a very low ve in mid range RPM. My VE table just doesn't look right. And also, when I tune VE to correct lambda and change lamda target table after that, lambda readings are not as they should be. Another issue i found, when IAT values rise, my lambda values go lean.

I allready thought, that my Injectors are probaply not set right? I've got 750cc five-o-motorsport injectors (flowtestet by five-o-motorsport, actually 755cc) and injector dead times are also set right. I allready checkt fuel pressure, it's correct.

Engine is a SR20DET, bored to 87mm, 9:1 CR, BC Stage 3 Cams 272°/272° without VTC, stock s15 ball bearing turbo, bosch 2x2 wasted spark, NGK 2668 (BKR8EIX) regapped to 0,4mm.

Somebody got an idea?

[derOJ]

Did you try another Lambda Sensor?

Checked the wiring to the Lambdacontroller?

Lean reading could also come from unburned fuel/air mixture. Maybe your ignition timing is much too late? just an idea...

[Thilo]

No, but the bosch 4.2 isn't that old. But I also do not have another one to try.

Wireing is ok. I've got the Lambda controlled by the EMU.

Timing isn't late in low pressure area. I attached my Tuning file, maby you could give it a quick look?

[ihiryu]

Are you using the onboard wideband or an external controller? Did you check for exhaust leaks?

If you're using the onboard make sure you click "Enable Lambda Filter"

[Thilo]

Controlled by the EMU.

I think, i've got a tiny leak in my exsaust manifold, because of the EGT sensor. Does this influence Lambda readings that hard?

[ihiryu]

Any air leaking could do it. Do you have the lambda filter enabled?

[Thilo]

Yes, I have. Ok so I will try to get it all leakproof and then post a reply. Thanks here

[A.Dutsov]

I dont have any leak, and my car wants same VE, its same engine, so maybe this engine wants that VE shape to run in the desired afr ...

[Sm887]

If you could post a log file, it would have been easier to help.

[nickbmw]

Injector linearity will affect the VE numbers needed. I wouldn't pay any attention to the lower ve numbers needed at the midrange.

Regarding the issue you have with lean afr when iat is rising, read here :
viewtopic.php?f=19&t=8817

[Thilo]

Hi,
just to give you a quick update:

I've got a complete new exhaust (which doesn't leak) and lambda readings are still bad at overrun, but hey, dont give a fuck, i think the fuel is just not burning right at overrun. My timing isn't late at overrun (something between 35 and 40 degree btdc). I really don't care, engine is running good, but just for my interest in engine physics, does anybody know, what's causing that phenomenon?

I also got my problem with the weird looking VE table under control, I just manualy flatend out the table and voila, engine is running at desired lambda. I think autotuner just pics too much transient data and has a problem with this rpm/map area.

The engine heat soaking problem has also almost gone since I managed my IAT to be heat shielded and vented my engine bay. The rest does the EGO correction

Thanks for helping
Thilo

[PSI-Motor]

You know that you shouldn't give the engine any fuel during overrun?
Of course your lambda won't show realistic numbers during overrun, no air into the engine + exesive fuel = kaoz for the lambdasensor.
Your sparkplugs, oil, lambdasensor, cylinder walls hatching will take a beating.

[nickbmw]

You have to set the fuel cut options correct. In this case, the fuel under (kpa). 17-20kpa is fine. It's not good for your engine to inject fuel at overrun, like mentioned already, plus you are raising your fuel consumption.

[Thilo]

Yes I know that, I was just hoping for some sort of popping noise and overrun flames