tsherriff

Is it normal for the AFR to fluctuate at idle and at cruise on the highway?

I was told that at idle and cruising at highway speeds, it should stay at 14:7 AFR, according to AMS in D.C.

I have an AEM wideband and ever since I got my first custom flash (only 700 miles on the car back then) in Tacoma, Washington it has always fluctuated from 14:4 - 15:2 at idle and at cruise on the highway. Is this normal?

When I accelerate (21 psi), it drops down to 10.8 then back up to 11.5 and holds pretty much till redline.

Johnboy1065

iTrader: (6)

AFR fluctuates all the time. what really matters to the health of your engine is your AFR under full throttle. and 10.8-11.5 is safe

Pr3z

iTrader: (14)

No your car is going to blow up! RUN TO THE NEAREST BOMB SHELTER!!!





Seriously though yes it's perfectly normal.

saiyanzzrage

iTrader: (11)

perfectly normal, what you need to worry about is your AFRs under WOT and between 10.8 and 11.5 is beautiful

tsherriff

I was getting worried, because AMS told me that they never seen AFR fluctuate at idle. They said that all th eother cars they've tuned stay right at 14:7. I couldn't understand this since the car has always done this from the beginning. Now what I am worried about, is that the AFR does spikes to 11:95 at peak torque (23 psi), then drops back down to 11.3-11.5 till redline. This only happens for 23 psi or higher. I've changed the plugs, front o2 sensor, walbro fuel pump, did a leak down test. Everything is fine. I don't know what else to do? The car seems stronger at 22 psi than at 23 psi and higher. Currently making 330 awhp/340 torque at 21.5 psi...

Johnboy1065

iTrader: (6)

11.95 is still ok. I just try and keep my AFR real safe. like below 12.3 or so

burgers22

At cruise and idle I can see the ARF going either side of 14.7 as it's suppose to. My ECU+ has very good resolution, so it's easy to see.

If your car feels stronger at 22psi you could be picking up some knock with the increased boost, can you log knock with Mitsilogger or Evoscan?

MB