AFR using Nitrous/Propane?

[Catwood]

Anybody care to state the range under WOT? Blower motors like it fat, same for nitrous? 11.8 to 12.5 is my guess?



Thanks,
Carl

[1TONY1]

Call BTR. I think Tom (BTR) tunes his safer then a 12 anything. I run my f-body at 11.6

[Russ M]

It depends on the octane of the fuel you are going to be using. For pump gas mid to upper 11's are what you want, for good race fuel mid 12's are ideal.

[Catwood]

If I run at the track I'll run unleaded race fuel. I think it's 103 octane. However on the street it will be California's lovely 91 octane.

I did pull a dyno sheet from the previous owner. There is only one chart with AFR. I have no idea what jets they ran but RWHP was 640 and RWTQ was 768. AFR was about 14.1 when the nitrous hit. At aout 3300 RPM AFR jumped to 17 and declined from there. At about 4200 RPM it was still at 14 and by 5000 RPM it had dropped to 12.5. It looks like they pulled to 6000 RPM and AFR was 12 when it was shut down. Jet's were changed to 40 propane/55 Nos and it pulled about the same HP but RWTQ jumped to 817. No AFRs were recorded on that pull.

Guess I'll call the dyno shop to see if they retained the data otherwise it's back to the dyno we go.

Thanks,
Carl

[Snake Bitten]

17 when you are making the most torque??? That's too lean...get to the dyno and tune...shoot for 11.5 like Tony said...

[Jack B]

Carl:

You are definitely flirting with detonation, fatten the propane or lean the NOS. You will put out more hp running leaner (ideal 14.7), however, it could be at the expense of the engine. You can get away running a NA viper in the 14's, not on the bottle though.

The propane bottle temp/pres is also critical. Keep track of it, if it is not at 180 psi it will also force you to run leaner. I would pull all the plugs to make sure you have any tips left. Make sure you also have a colder plug without an extended tip, you don't want the oem plug in this car. Prior to dynoing again I would bring the NOS down to 50-52, you are on the edge.

There is no sense in pulling to 6000 on the dyno, your max torque is about 3500 and the max hp is about 5000, going further is meaningless.

[BigCarrot]

Wow! That's scary lean! Lean is good if you're talking about meat or women, but a car on the juice does not need to be lean!

[Catwood]

Yeah I agree. Time to get to a dyno.