RussellR

Normally I use 91 octane in my '07, going to the dragstrip this weekend and they sell 100 and 104 unleaded there.

My questions are,

Will there be a benefit, meaning a quicker ET by using the higher octane on that day?

How long does it take the computer to readjust timing and whatever it needs to for the higher octane?

Car has a cam and headers if that means anything

thanks

Russ

PowerLabs

The benefit is that if your car runs very agressive timing or AFR curves and experiences knock retard when driven hard, it will not knock with the race fuel, so you won't lose power you may othrwise have lost on the strip.
If the car is tuned conservatively for 91 octane you will either gain no horsepower, or may lose some depending on the particular fuel you are running.
My advice would be to put a little bit of the cheaper race gas for safety as an octane booster, but I wouldn't spend the money on a full tank of it unless the car was tuned specifically for it.

patton

knkali

Hoonose

93 octane for max performance.
12 gallons of 91 octane plus 4 of 100 works out to a 16 gallon tankful of 93 octane.

http://www.motortrend.com/features/p.../photo_03.html

seevi

With the 100+ octane fuel, you can advance your timing a bit, what that will get you it really hard to say. Afterward, you would have to retard your timing for street use. A lot of work for little real gain.

I blend 91 octane pump gas with 100 octane racing fuel to reach 95 octane. I used to have a problem where the computer started backing spark out before the shift as a result of pump gas quality. Making a mixture of 95 octane did eliminate that problem and there was a little decrease in et in the 1/8th mile.

Regarding the computer learning the new fuel. I can tell you that mixing the fuel at the track made no noticeable improvement. Blending the fuel and driving 15 miles to the track was noticeable. Engine idle was smoother, and the car ran smoother.

RussellR

thanks guys! I was under the impression that the Computer always trys to advance timing to the maximum before ping.

I'll just stick with whats in it, I need to learn how to launch the car anyway before I worry about shaving off another hundredth or so. lol

russ

455HOGT37

I thought the computer pulled most of the timing above a certain inlet temperature (86F?). If this is the case, high octane won't help you at all.

PowerLabs

Up to a maximum that is programmed into it. From the factory that maximum is very conservative since they have no reason to assume you would run any fuel other than 91 or 93 octane.