Thread: Need Help on Octane

Tweet

With this drag only car we've been building, we're getting close to the first fire up and will need to break cam in. Motor is 11.2.1 SCR. Have some questions on fuel:

1. When i do race the car next year, will i need to run 105 or 110 octane or something else? Need some advice.

2. For the first fire up and cam break in, do i need to use one of the above fuels or could i get away with 93 pure octane for this process?

Thanks

To build reliability in a race car, you need to eliminate the variables.
Fuel is a variable that you can control easily. For tuning purposes, I'd say run the same fuel you're gonna race with.
That way you won't have any surprises come race day.
(well.. at least one less surprise right? LOL)

Originally Posted by 34_40

For tuning purposes, I'd say run the same fuel you're gonna race with.

I'd say the same thing and don't risk spoiling your new race motor with detonation from pump gas.

.

Just to add more perspective to the guys, you only need enough octane to keep the engine from knocking, any more than that and you don't get the benefit of the additional octane rating. More than c.r. is involved. Generally it's all the factors that relate to heat of combustion that will drive octane requirement. Air temp, load, timing and so on all contribute to the outcome. At break in you won't have much load on the engine. Depending on whether you fire up in a heated shop or outdoors may change charge air temp. I could go on, but you probably get the point. Now, all that being said, you're doing a break in procedure, with a bunch of unknowns. Covering your butt with "too much" octane rating is one of those safety factors that doesn't cost much if anything at this point. So I'll join Mike and Richard since it's the safest advice given the knowns. It's later, when you're in mortal combat on the strip, that optimizing your octane rating requirement becomes more critical.