Analyze AFR and Dyno

[sw20kosh]

Here is a Virtual Dynograph of my completely stock ROM on a completely stock car.

Why is there a weird AFR bump in the lower rpms. I looked at the actual ECUTEK logs and it is indeed there on both WOT pulls. It happens well within WOT so it isn't partial throttle or anything. Is this normal or something to be concerned about?



here is the log to go with it:

green = AFR
blue = fuel rail press
red = fuel trim long term
yellow = fuel trim short term

[jamesm]

i'm guessing that's a stock o2 sensor that hasn't been scaled down. if that's the case, the you're just seeing a tiny bit of what's going on there, the moment that the came above 12.x:1 before settling somewhere lower in the range.

it's not uncommon to have a bit of motion in the afr when you first step on the throttle. normally if it's really bad it'll be because of throttle delta compensation requiring some adjustment, though without a wideband you won't be able to tell for sure. it can take longer than you might imagine for the afr to settle down to target, especially if the calibration isn't spot on.

i wouldn't worry about it unless it's presenting a driveability issue.

[sw20kosh]

Originally Posted by jamesm

i'm guessing that's a stock o2 sensor that hasn't been scaled down. if that's the case, the you're just seeing a tiny bit of what's going on there, the moment that the came above 12.x:1 before settling somewhere lower in the range.

it's not uncommon to have a bit of motion in the afr when you first step on the throttle. normally if it's really bad it'll be because of throttle delta compensation requiring some adjustment, though without a wideband you won't be able to tell for sure. it can take longer than you might imagine for the afr to settle down to target, especially if the calibration isn't spot on.

i wouldn't worry about it unless it's presenting a driveability issue.

Thanks! Ya its stock O2 with stock ROM.

What about fuel rail pressure tapering off at higher RPMs like that? Not a concern? I have a high flow fuel pump in the tank and I just removed a supercharger which required tampering with the fuel rails. Just want to make sure I didn't mess anything up.

[jamesm]

Originally Posted by sw20kosh

Thanks! Ya its stock O2 with stock ROM.

What about fuel rail pressure tapering off at higher RPMs like that? Not a concern? I have a high flow fuel pump in the tank and I just removed a supercharger which required tampering with the fuel rails. Just want to make sure I didn't mess anything up.

that's not port injector fuel rail pressure you're logging, but rather for the di system. notice the pressure is around 20MPa, which is roughly 2900psi. i haven't noticed in my logs whether my car does the same thing, but then i haven't really been looking for it. i can check some old logs and let you know what i find.

[FA20Club.com]

They all taper in the higher rpm range unless you change it for a specific reason.