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How Bad Are These Afr's?

kawasakirider

By kawasakirider,
in Engines & Forced Induction

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kawasakirider Grand Master

kawasakirider

Posted
Posted

Hey everyone, my car is tuned like shit at the moment, but it's going in for a tune next week. I've been reading up on AFR's and it seems at idle it is really lean. Could this explain why it's hard to start?

66419D25-DA6F-4DA0-8D86-5345A9A28936-8779-000002CD73197DB5.jpg

Would you guys advise not to drive the car too much before it's tuned?

The car is a Z32 TT.

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GTSBoy Grand Master

GTSBoy

Posted
Posted

Point 1: There is no idle AFR shown on that dyno chart. The run starts at 55 km/h.

Point 2: The AFR starts at about 15:1 at cruise (in 3rd or 4th or whatever gear the run was done in) which is ever so slightly lean but otherwise pretty normal.

So , no. I see no problem there.

Point 3: The AFR is perhaps ever so slightly lean in the region around 135km/h, which is near peak torque, right in the fat of the midrange. If it is going to ping, it will do so there. 12.5:1 is probably safe, but depending on the engine, might be a little too lean. But not a massive problem. I would say, given that it is richer at lower and higher revs than that, it could easily be tuned to flatten out the AFR in that region, should you want.

R32Abuser Mentor

R32Abuser

Posted
Posted (edited)

All seems OK but could use with some touch ups here and there (depending on the motor and its sensitivity to detonation)...

Especially rolling onto peak torque as this is where the motor will have the greatest tendencey to ping/knock. 12:1 is OK but depending on the application, I'd be tempted to go a little richer.

As for idle, the dyno graph gives no information so cannot comment.

EDIT: GTSBoy beat me to it...

Edited by R32Abuser
Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted (edited)

I would make it a tad richer (11.5:1) as it approaches MBT (max torque) then bring it back to 12:1 all the way to the rev limiter.

EDIT: R32Abuser beat me to it

Edited by johnnilicte
Lithium Grand Master

Lithium

Posted
Posted
I would make it a tad richer (11.5:1) as it approaches MBT (max torque) then bring it back to 12:1 all the way to the rev limiter.

MBT is not an RPM specific thing, and 11.5:1 is quite rich for a low compression motor running 6psi...

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