SR20DET Wideband A/F Ratios

[RedOctober13]

Before I start, yes this topic is all over the place. But I can't seem to find any relevant info in my case. Please comment based on experience only.
14.7 is stoichiometric, the obvious.
S13 Blacktop SR20det
At idle I'm bouncing around at 14ish. Mostly close to 14.7. WOT I'm hitting 11-12 on my AEM UEGO wideband. BUT when I'm cruising, (mostly all gears) I'll hit 15 sometimes even 16 when I'm cruising around 3k rpm 10-25% throttle. Anybody experience this? Is this normal under cruising at different loads? Sometimes I see the spike hit to high 15's and 16's so I step on the throttle a bit to get it down to low 14's 13's. Other times when cruising I'll be at 14ish but around half the time I'll hit that 15/16 spike. A friend of mines says he sees 12 on the wideband anytime he hits that throttle. Only 15/16 when he lets off the gas
I don't have any exhaust leak (that I know of)
Here's the part list if it help-
Stock e5 ecu
Full Nissan oem gasket and seal reseal
Blitz intercooler type se
HKS bov (vented to atmosphere)
Tomei bottom mount turbo manifold
Tomei elbow
Stock t25 journal bearing
Megan downpipe (catless)
Megan test pipe (AEM wideband is mounted here)
Tomei full 3.15 in exhaust to the back

Oil pressure is good
Boost and vacuum is good, max boost is around 9ish psi
WIDEBAND A/F ratios while cruising is my problem.
Any input is appreciated. Thanks.

[anti tyler]

I think it's all in your head.

you don't want to be washing the cylinders with fuel while you're at a neutral load just "cruising" unless you have like an SAFC or some sort of live data display, I think your 10-25% throttle in reality is more like 5-15%. Which is why you're seeing that 15-16 offset on air/fuel mix.

I think you're in reality on the boarder line of not producing positive pressure, so you're nearing the peak where a boost gauge would start to take a sharp dive into a vacuum

As long as when you're getting into it they drop, raising fuel mix, then you don't technically have a problem.

[Kingtal0n]

Pressure drop because of large intercooler plumbing while using a maf sensor placed before the turbo is what causes the lean tip-in (if you are saying when you push down slightly on the throttle it goes to 15's and 16'). The solution is to use a map sensor, however I wouldn't worry about it, there won't be any harm.


On the other hand, if you are cruising along at 14.7 while using closed loop on the narrowband (does it have a narrowband closed loop control?) and it wanders into the 15's and 16's for a minute or stays there, that is a sign of a bad O2 sensor (narrowband).

On the other, other hand, if you are cruising along in OPEN LOOP and not using a narrowband, and the wideband wanders and stays in the 15's and 16's this is a sign of a leak between the maf and compressor inlet, or otherwise, a bad (dirty) maf reading, or filthy injectors, or low fuel pressure, or the engine needs tuning.

[TheRealSy90]

I'm sure the VTA bov could have some hand in it as well when in vacuum.


Honestly 15-16 is perfectly find at partial throttle if you aren't in boost and just cruising.

[carcrazee]

I think youre good man, 15-16 afr is pretty normal for light throttle/cruising, highway driving like 14.4-14.8, you want to be any where between 11-12.2 at full throttle, 16+ when youre off the gas

[hanzbrady]

Another thing that people still running stock ECU's forget to consider is the conservative timing map working along with their AFR's. From what you said you're fine. If you we're running a standalone with forged pistons running some kind of race fuel trying to make 1000HP I'd recommend some changes but like I said for the set up you have seeing the 15-16 AFR's, especially in parts of the map for low power cruising is perfectly fine.

[KAT-PWR]

I've spent 20k miles with a 16 cruise afr
Normal, most nissans can handle running lean on cruise for mileage. It's not a batch fire/wasted sparq car.

[RedOctober13]

Super helpful response coming in, thanks guys. I think you're all right. Not sure if Nissan's stock ecu switches between closed and open loop but like I said, the problem is only while cruising and I get that spike. Just really picky about how my car runs, but I never really thought about the positive pressure and vacuum while the car is doing that. I'll keep an eye out on my boost gauge that reads vacuum as well.
It's running a mostly stock setup with bolt ons, stock MAF and original o2 sensor btw.
I'll check sparkplugs soon and see how it's doing, last time I pulled it about a month ago it was fine. I'll keep on monitoring it based on the info here.
Thanks for all the feedback!