Is my AFR of 13:1 ok for HPDE use?
#1
Team Owner
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CI 3-5-6-7-8 Veteran
Is my AFR of 13:1 ok for HPDE use?
Here's my latest dyno graph after getting tuned post cam.
Should I be fine on pump gas or add some 100 octane for summer track events?
Does't the car richen itself up as it gets hot anyway?
Any input from tuners/experienced people would be much appreciated.
Should I be fine on pump gas or add some 100 octane for summer track events?
Does't the car richen itself up as it gets hot anyway?
Any input from tuners/experienced people would be much appreciated.
#2
Safety Car
If your knock sensors are active they'll pull timing if needed - I doubt they will need to. If I remember correctly - didn't Jeff at Carolina Motorsports tune your setup?
#11
Safety Car
#13
Former Vendor
Hot inlet temps during long use is hard on the motor.
Did you guys know that it is ok for the gas stations to have up to a 10 percent cross contamination per pump??? So that means you can have 10 percent e85, disel, 87, 89, or even water.
Randy
#14
Race Director
Randy, I didn't know about the 10%, but I DID know they pump all of the fuel through the same pipelines (with no definitive break in between), so mixing certainly occurs at various stages of the processes.
Even a stock car can have some detonation, especially at high temps, so a little race gas is never a bad idea. Whether it's worth the money these days, well that's another question....
Even a stock car can have some detonation, especially at high temps, so a little race gas is never a bad idea. Whether it's worth the money these days, well that's another question....
#16
Safety Car
The higher octane helps eliminate pre-ignition, but does not necessarily add power unless the engine is built for it. So my question is - what makes a higher compression engine more prone to pre-ignition and detonation, and why can't a lower compression motor get more out of higher octane?
I have a 383 motor built for track use with lots of high end power and a flat torque curve, but stock compression for longevity. It actually seemed to have more power when I ran it Saturday on 93 with a bottle of OTC octane boost. Sunday I filled up with 100 octane and it seemed to have the same or less HP...
My imprecise measureing stick is a buddy's car, we always run together and i can differentiate by how much I pulled on him on the back straight.
#18
Safety Car
Gases will explode at a certain compression without a spark. With a high compression engine and lower octane fuel, the fuel reaches this point before the piston is at the spark point. Adding octane basically makes the fuel less volatile, avoiding the ignition without the spark. Thus adding octane to fuel that does not need it will do nothing, the fuel will ignite when the spark reaches it.
#19
Drifting
You could even lean it out a bit at lower RPMs.
13.1:1 is fine across the board, speaking of HPDEs specifically. Keep in mind stoich is 14.7:1. I datalogged mine and had "0" knock retard all over the maps. You can even try advancing your timing 5% at a time and see if you get any knock. But I would avoid race gas regardless.
13.1:1 is fine across the board, speaking of HPDEs specifically. Keep in mind stoich is 14.7:1. I datalogged mine and had "0" knock retard all over the maps. You can even try advancing your timing 5% at a time and see if you get any knock. But I would avoid race gas regardless.
#20
Safety Car
Gases will explode at a certain compression without a spark. With a high compression engine and lower octane fuel, the fuel reaches this point before the piston is at the spark point. Adding octane basically makes the fuel less volatile, avoiding the ignition without the spark. Thus adding octane to fuel that does not need it will do nothing, the fuel will ignite when the spark reaches it.