Stock AFR ratio

Z_ealot

Anyone know what the stock AFR ratios for our cars are at WOT? I'm getting conflicting information from two sources and would like a definite answer if anyone can provide one. Thanks!

ByThaBay

3.7L stock fuel targetsstockFuelTargets.jpg

These are set intentionally rich from the factory because there is no fuel control on this ecu during open loop. You can add an open loop fuel control strategy by installing ecutek on the ecu.

Z_ealot

Thanks man, appreciate it very much... just needed it to confirm I'm tuned properly cause i have a nissan "tech" telling me that factory afr at WOT is 13.5 to 13.8 and i had my tuner telling me that stock afr at WOT from factory is 11.5, looks like I'll trust my tuner over the tech

ByThaBay

The targets vs what the car actually will do vary from vehicle to vehicle. It’s entirely possible that because your tech doesn’t have access to the afr target info he’s only looking at the resulting exhaust and seeing what he sees. Tuning the car should fix this and allow the vehicle to hit targets. Can’t really blame the guy in some cases he’s probably right.

ByThaBay

To confirm you’re tuned correctly plot the afr target against the actual afr for each bank and the lines should follow each other relatively close. As far as the targets themselves, that becomes tuning preference based and each tuner can have his own targets that he wants your car to hit.

Z_ealot

Already done and they follow each other exactly like they're supposed to, only reason this came up is because I've been burning oil and did a compression test to check the piston rings, all cylinders were good with the exception of 3 and 5 which were leaking, both tested at 210psi hot and 260psi hot/wet but lost about 20psi over the course of 1 minute with the leak becoming slower as pressure went down, tech suggested that afr was to rich and was fouling the oil and causing it to burn but the readings and targets refute that so I'm trying to get a leak down test scheduled at the dealership to see exactly what's going on

SonicVQ

What was the compression pressure for each cylinder?
For reference, the factory spec is:
•*Standard: 242-341 PSI
• Minimum: 178 PSI
•*Maximum cylinder to cylinder difference of 14 psi

How much oil does it burn?

Z_ealot

210 across all cylinders hot and dry, between about 250-260 hot and wet across all cylinders. The only exception is cylinder 3 and 5 which start out at the same psi as all other cylinders but then lose about 20 psi over the course of a minute. As for how much oil is burning, keeping track of it since this last oil change i did it had burned a half quart in just under 1500 miles. Also threw a vacuum gauge on it just to test out and vacuum gauge reads a steady 16 in/Hg which seems like something's up there but talked to my tuner and he insisted it's fine. Also checked cylinders 3 and 5 with a borescope and they show no obvious signs of head gasket failure, still have a nice thin coat of carbon on each of the piston tops so not sure what's going on. Only thing i don't have available to me and I'm not capable of doing where i live is a leak down test which I'm trying to get scheduled at the dealership

SonicVQ

Was the accelerator pedal pushed to the floor?

Compression gauges have a check valve so the pressure doesn't drop to zero after cranking has stopped (where a intake/exhaust valve may be open)
IF after your test, the pressure dropped, that is a gauge issue, not a cylinder issue.

1 quart in 3,000 miles is in the normal range and you don't need to worry.
Start to worry when it burns a quart in 1,000 miles.

Assuming the gauge is accurate, my stock VQ37 has an intake vacuum at hot idle of around 22 in/Hg.
You might be on to something here...

If this was my car, I would not worry about anything and just drive it.
However, for your peace of mind, I hope you can get a leak down test done.
Good luck!

Z_ealot

Thanks!