What's running lean?

[robmustang201528]

Just got a tune and cold air Jlt. Made 410hp at the wheels.im pretty happy with it but u always want a little more. Tuner said the computer was pulling timing out of the car looks like a fuel issue. Burn it out drive it a while put a different gas in there and should see an improvement in power. I told one of my friends my air/fuel ratio and he said 13.8 14.2 is to high that im running lean. Is that true? Is this normal? Air to fuel ratio? I was running 65mph @ 14.3 air fuel ratio is that normal?

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[Grimace427]

At WOT you should see 12.0-12.5 on a datalog(0.82-0.85ish Lambda). At cruise you can see as high as 15.0:1 with no problem. You should be reading a Datalog to get this info, not a tailpipe sniffer or the gauge on the dash(while accurate enough, it doesn't display fast enough at WOT).

 

[JimmyTwoTimes]

At WOT you should see 12.0-12.5 on a datalog(0.82-0.85ish Lambda). At cruise you can see as high as 15.0:1 with no problem. You should be reading a Datalog to get this info, not a tailpipe sniffer or the gauge on the dash(while accurate enough, it doesn't display fast enough at WOT).

Air/fuel ratio is the only gauge I have that REALLY varies drastically. It'll bury the needle on the right during deceleration.

 

[Vinny@JLTPerformance]

Air/fuel ratio is the only gauge I have that REALLY varies drastically. It'll bury the needle on the right during deceleration.

The injectors turn off on decel when you come off the throttle, this is normal for most vehicles.

 

[BathS550]

AFR will bounce around excessively lean at idle or partial throttle.The only time you should be concerned about AFR being lean is at WOT. Start by datalogging and go from there.

i.e. do not concern yourself with afr when cruising at 65 as the OP mentioned.

 

[OppoLock]

Worth watching to get acclimated with timing and A/F basics:

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