13.1 AFR in a pro-mod

[jakesz28]

Here is a quote from a guy that tunes promods

I am not sure what lean enough to hurt parts is. I have had some stuff so lean, it slowed the car, showed weird stuff in the EGTs and actually made the plug dark, because it was so cold in the chamber, but I have seen very few, if any pistons, I thought were burned from lean. The only time I thought I had personally burned one lean, was when I had some super flyweight, thin on top, Super Stock pistons in a motor I was hosing. I burned holes straight thru the center and thought it got too lean. But looking back, I think the piston just could not take the cylinder pressure, cracked the center, forced some oil up through the crack and burned a hole in it. At this point, provided you have enough timing out, I think you will noticably slow the car, before you get the tune lean enough to hurt parts. I realize we don't all run Pro-Mods, but the lessons learned there carry over. These guys just want to go fast and are willing to sacrifice some parts to do so. We keep getting leaner and leaner, the cars keep getting faster and as a bonus, we are not hurting parts. We went as fast as 3.94 @ 190 with Myers car last year and it weighs 2500lbs. On top of running well, we did not hurt the motor once all year. It came apart twice and that was for rings and rods, never because it was hurt and I run the tune ups in that car really lean. Well over 13.1 on the 02 sensors.

Monte


This is just a food for thought. I keep hearing and seeing people tell others to run afr's in the 10.5 -11.5 range. Hell I never even logged my afr last year on any of my nitrous passes. I wonder were I was but I did get the plugs to burn clean. I was 12.8 on motor which could be a little rich after seeing were he runs his tunes.

[joelster]

I am at 12.8ish-1 here. No sense in changing the tune for the nitrous when you can just jet the nitrous a touch richer.

[Grr]

yeah i try to keep my cars N/A around 12.8 at peak tq and ramp them up to 13.3 at k7. Seems to work great and i kept picking up power up to that point

[ksmyss]

fwiw we never had a/f gauges on the pro mod i wrenched on. we would just read the plugs after every pass and watch the egts. we would get 1-2 weekends out of a motor but at the time, early 90s, there was still alot od nitrous experimenting going on. 2-3 bottles, 3-4 stages, dry shots. you name it we tried it.