what should my Air Fuel be?

[gnkid1987]

i just pulled my gn out of hibernation since 3 years. i did the bascis plugs, oil change etc and the car runs good. i put a new turbo tweak chip in i have a stock motor with T/A performance headers Precison PT51 turbo and 55 lb injectors. i want to run as quick as possible was hopeing for low 11s. all other mods are in my sig. byt what should i be looking for for an Air Fuel reading if i run 25-29 psi? thanks for any help

 

[TurboDave]

I didn't see any mention of what Widaband O2 sensor you're running to measure the air fuel ratio.

 

[Red C5]

What gas?

 

[gnkid1987]

sorry about that im running 93 octane gas with alky control using m1 methanol. the wideband is the innovate mtxl1 the new digital one. thank you

 

[TurboDave]

I hope you really dont expect to run 29# of boost on 93 and alky! 25 would be pushing it, 29, and you'll be looking for pieces of head gasket for sure.

Anyway, from what I've been told, when runnning 93 and alky, a good target A/F ratio to shoot for is something in the 10.8:1 range. I personally don't run alky so I'm able to reach a good tune at 11.4:1 But with alky you need to run richer A/F numbers.

 

[Red C5]

I can't comment on what a/f for meth, I think that completely changes tuning parameters. With just 93 I think 10.5:1 is about right.

 

[Timbuick]

To add to the OP's question, as i'm considering turning my boost up from the current 20lbs of boost, based on Turbo Dave's comments above, what sort of octane fuel should be used in addition to ally for higher boost?

 

[dpasadena]

To add to the OP's question, as i'm considering turning my boost up from the current 20lbs of boost, based on Turbo Dave's comments above, what sort of octane fuel should be used in addition to ally for higher boost?

I used to run 30psi on a stock longblock with alky/91 for over four years on a daily driver. Many, many 30psi hits on the street. Kept an eye on the tune and this was with a single nozzle. 23/20 timing(verified) . Wot target was 10.7-1. Never had knock retard.

 

[bad V6]

I've ran as much as 32.9 # on 93 and alky, timing at 21/19 and AFR was 10.5 with 0 knock, on a stock longblock with bolt-ons. I always tuned a little to the rich side so as not to have any knock, although I'm sure I was leaving some on the table, best time was 11.3 @ 117 MPH.

As long as the car is mechanically sound, with a good tune and set of stickies you should be capable of mid 11's pretty easily. Ease into turning up the boost and make small adjustments to stay on top of the tune.

 

[Timbuick]

Thanks guys. my question is pertinent as here in the UK our fuel,is lower octane so I have to be careful. Our 'regular' 95 fuel is actually 91 by US standards.

 

[bad V6]

Use caution when tuning and steer clear detonation.

 

[Timbuick]

Always careful with knock, the few strip-runs I have done involve me staring at the KR reading on the Scanmaster. No dramas yet.
I can get higher octane fuels (95) at some petrol stops.

 

[gnkid1987]

thanks for the help guys i have been slowly tuning the car and plan to take it to the track next month. im at 23psi right now and the af is 10.5 i will turn up the boost slowly and see how it goes. the engine is a stock long block that was re built 7 years ago only has about 8k on the motor. no smoking no noise at all and runs very smooth. i will update when i get closer