Air Fuel Ratio

[86bluecobra]

Whats the desired AFR for idle? My car is around 13.8 afr at idle when it is cold as the engine warms up is goes to areound 12.3 or 12.4. I think this is a bit rich and i think i could set it a bit leaner. how lean is 2 lean?

 

[Grn92LX]

Mine is around 16-18:1 at idle when its cold. It usually richens up to around 15:1 when it warms up. You're WAY too rich wasting gas!!

 

[86bluecobra]

lol with the price of gas i guess ill have to lean it out a bit. nice thing about carb's its so easy to do.

 

[86bluecobra]

I was told buy a holley carb guy today that a 12 to 1 afr at idle is a little rich but not much for a car with a largerish cam. Personally i didn't think the XE274 was a very radical cam. He also told me that what i want is a 11.5 to 1 AFR on the juice. What do you guys think? BTW my car was running 11 to 1 when cruising at 55mph (80km's) and in the 10 to 1's when at WOT. I guess on the juice i'm getting more then enough fuel mixed in. I have not been able to run the juice with the wide band because bottle is empty. Also would it be wise to run another O2 sensor on the driver side so that i can see whats going on with that bank with a toggle switch?

 

[Grn92LX]

You want around 14.5-15.5 at cruise. 11:1 at cruise??? Holy wasted gas batman!! YOu need some serious tuning on this carb.

On motor @ WOT you want around 13.0-12.8 ish. On spray i'd shoot for mid 11's or so.

 

[Spot U 2]

14.7 to 1 is ideal.

 

[bluevenom867]

Eh,yea you need to lean it out a bit....

You will probably get like a 14.5-15:1 for cold idle,13:1 for warm.

For WOT on juice you want 12-11.5:1,but the motor tune changes a little when the juice off as when its activated it can mess with the carbs booster signal (so you will need to paly around little here and find out what your carb likes best when off bottle and on bottle as far as FP and jetting).

Also,nitrous engine generaly richen up at the top end,so 10:1 is normal (at end of rpm range,WOT).

 

[86bluecobra]

well guys usally complain that my car smells like raw gas and seeing the numbers my car is making makes me know that They are not exagerating. first things first though i need to get my valve train adjusted proper so that i'm making the proper vacuum at least a even vacuum then i need to get timing straightened out then i will worry bout afr. but with gas prices the way they are leaning it a bit is probably a good idea.