switching to hi octane
Thread Starter
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Joined: May 2008
Posts: 92
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From: Longmont Co
switching to hi octane
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
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
Le Mans Master
Joined: Oct 2007
Posts: 6,149
Likes: 11
From: Greater Detroit Metro MI, when I'm not travelling.
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
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
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.
Safety Car
Joined: Jun 2004
Posts: 3,560
Likes: 739
From: panama city beach florida USA
St. Jude Donor '09
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.
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.
Team Owner
Joined: Feb 2000
Posts: 53,529
Likes: 77
From: Arizona
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
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
Burning Brakes
Joined: Aug 2008
Posts: 802
Likes: 6
From: Oro Valley AZ
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.
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.
Thread Starter
Advanced
Joined: May 2008
Posts: 92
Likes: 0
From: Longmont Co
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
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
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Le Mans Master
Joined: Oct 2007
Posts: 6,149
Likes: 11
From: Greater Detroit Metro MI, when I'm not travelling.
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.