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Discussion Starter · #1 ·
My local drag strip sell both these octanes. I also know that adding TOO high a fuel upgrade will hinder performance as the compression isnt there to give the proper combustion. I have an FRPP tune/snorkel, FMIC... last time i ran, it went 100 mph through the trap; Do yall think the octanes are TOO high to see any added benefit? Or will I see improvements? (djformoney told me to run half e85 and 7 gallons of 93 to make a e15 mix which the car can handle without a tune, although im not sure im comfotable with that yet, if that s the case can i just put straight e15 in the tank?? also thanks to djformoney for the help in the Pm's)

these fuels are unleaded and non oxygenated
 

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My local drag strip sell both these octanes. I also know that adding TOO high a fuel upgrade will hinder performance as the compression isnt there to give the proper combustion. I have an FRPP tune/snorkel, FMIC... last time i ran, it went 100 mph through the trap; Do yall think the octanes are TOO high to see any added benefit? Or will I see improvements? (djformoney told me to run half e85 and 7 gallons of 93 to make a e15 mix which the car can handle without a tune, although im not sure im comfotable with that yet, if that s the case can i just put straight e15 in the tank?? also thanks to djformoney for the help in the Pm's)

these fuels are unleaded and non oxygenated
To see gains from all of this that actually mean something you'll need a tune. Also, not sure how comfortable you are playing that kind of game with e85 on an untuned car...but I would NOT run half a tank of e85 without a tune. Anything over 1 gallon is recommended for a tune I thought...bad advice I think.

Edit:
http://www.focusst.org/forum/focus-st-performance/46995-e85-benefits-without-tune.html
http://www.focusst.org/forum/focus-st-performance/44020-e85-bone-stock-st.html
http://www.focusst.org/forum/stratified-automotive-controls/43850-e85-custom-tune-no-other-mods.html
http://www.focusst.org/forum/focus-st-performance/28248-anyone-running-full-e85.html
I'd recommend reading through these ^
 

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Discussion Starter · #3 ·
To see gains from all of this that actually mean something you'll need a tune. Also, not sure how comfortable you are playing that kind of game with e85 on an untuned car...but I would NOT run half a tank of e85 without a tune. Anything over 1 gallon is recommended for a tune I thought...bad advice I think.

Edit:
http://www.focusst.org/forum/focus-st-performance/46995-e85-benefits-without-tune.html
http://www.focusst.org/forum/focus-st-performance/44020-e85-bone-stock-st.html
http://www.focusst.org/forum/stratified-automotive-controls/43850-e85-custom-tune-no-other-mods.html
http://www.focusst.org/forum/focus-st-performance/28248-anyone-running-full-e85.html
I'd recommend reading through these ^
Yea I figured as much. My question was more specifically about 98 octane and whether I would see benefits. I understand that to see gains from a E tune but the computer recognize 98 octane and advance the timing the way it does when you go from 91- 93.
 

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Yea I figured as much. My question was more specifically about 98 octane and whether I would see benefits. I understand that to see gains from a E tune but the computer recognize 98 octane and advance the timing the way it does when you go from 91- 93.
98 Shouldn't do anything more than 93. At the most it will make your motor a little less prone to knock, but shouldn't really help with performance any more than that.

Sorry if I misunderstood your question!
 

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Unless you are tuned for it, it won't make a difference. The only cars that you can add octane to without a tune are constant closed loop cars. This is because they are always playing with timing to find the knock limit, higher octane means it can run more timing. Traditional open/closed loop cars only adjust when in closed loop (normal driving) once you are wide open throttle and/or past a certain engine load, the car goes into open loop when it runs a preset fuel/timing strategy.
 
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