o2 sensors and fuel trims

[Greg E]

Kinda on topic, but how much a variance in fuel trims is allowable between the 2 banks of cylinders? I'm talking about the lo and mid trims...

I'd see wonky trims on my stock 98. +6% front low, +2% Front Mid then turn around and see -7% Rear Low and +5% Rear Mid.

Got me why this is... Car runs butter smooth so it doesn't bother me.

[iceorphen]

finally getting around to tinkering with trims.. is it normal for the trims to remain a steady number..with 0 change? I have been driving for a few weeks and they are set at 12.5%. (both o2s cycle fine) front+rear mid+low are at 12.5% with the rear low at 12.3xxx. Just wondering before I go and mess with the VE if this is normal to have such "steady" numbers?

Thanks

[Greg E]

Your trims are max rich that's why they are steady. Better track down your vac leaks.

What injectors are you running?

[iceorphen]

Rc 660s

[DG]

I'd see wonky trims on my stock 98. +6% front low, +2% Front Mid then turn around and see -7% Rear Low and +5% Rear Mid.

Got me why this is

Small exhaust leak letting fresh air in at idle.

DG

[Greg E]

Small exhaust leak letting fresh air in at idle.

DG

I thought that at first too. But normally you can hear those little leaks. Even after removing the heat shields and inspecting them closely, I found no evidence of a leak.

Always figured it was a dirty injector or something trivial like that.

[DG]

Put a little Seafoam in and watch the fun.

I'm going through this right now trying to get my car to pass emissions. New injectors, fuel pump, and plugs but rear bank is reading way lean at idle and the O2 correction on that bank is huge. Back three cylinders full of carbon so poured a little Seafoam directly into those holes while I had the plugs out to help clean it a little. Fired car up and a steady column of smoke pours out from underneath the back turbo.

No audio indication of leak, but oh yes it is there - and the light goes on as to why the O2 correction at idle is so friggin' wonky.

DG

[iceorphen]

Upped my entire VE table +5 clicks (]x5) went for a longggggggggggggggg drive, and let it idle a ton. The rear mid began at ~10% and eventually settled on 12.5 again :|

Im going to reflash with +15 clicks and see where it gets me. Anyone care to share their injectors/pump and how much of an adjustment was needed? Curious to compare my results.

rc660s
hw wally400

[Greg E]

Hmm... Where did you get your injector from?

Can you post your injector scaling and latency values?

[iceorphen]

Injectors from maximal, scaling is @661
V mS
4.69 3.315
7.03 2.100
9.38 1.065
11.72 .630
14.06 .360
16.41 .180
18.68 .045