Is 91/93 octance required for 450rwhp on F/I?

groundpounder

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I'm going to be doing a DOB kit this spring. I won't be forging the motor so I'm going to be limited to the 450 rwhp. Do I need to run the more expensive 91 octane that I'm currently running on my N/A tune? My gut says I should run higher octane but what's the science say on it. Opinions?
 

stkjock

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Run the highest you have available if u like keeping the rods and pistons intact
 

ChewyR

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Well, opinion is yes. I guess you could experiment how well the knock sensors work, or how well the engine runs with 0 degrees of timing.
 

skwerl

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Why are you installing the supercharger? I assume it is for more power. Power is a result of mixing fuel, compression and timing. You can manipulate any or all of these three requirements in order to affect power output.

Reducing the fuel octane requires reducing timing in order to prevent detonation, which will destroy the engine. So spending thousands on a supercharger only to claim poverty and cheap out on an extra $7 per tank of fuel doesn't make sense (Premium is 60 cents more than regular, fill up takes about 12 gallons). I spend more than that for lunch every day.

You can dial back the boost, dial back the timing and run a tune that will be safe on 87 octane but you aren't going to get a hell of a lot of power. Which then brings us back to the original question of why you installed the supercharger in the first place.
 

MilehighGS

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Once you start experiencing when boost hits, you won't want to keep power at 450 and you'll kick yourself for even thinking of 87 octane.
I kinda said the same to myself.....limit power to 450ish..........last dyno was 485/497 to the wheels on a Dyno Dynamics dyno.....at 5200 ft..

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07 Boss

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I'm going to be doing a DOB kit this spring. I won't be forging the motor so I'm going to be limited to the 450 rwhp. Do I need to run the more expensive 91 octane that I'm currently running on my N/A tune? My gut says I should run higher octane but what's the science say on it. Opinions?


Haha, you’re kidding right?

Not forging the bottom end. Definitely run the higher octane. At least you don’t have to pay $7.99/gal for 100 octane.
 

zoomerman46

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So, if you want to run 450RWHP, at least three things need to happen
you need air, fuel and timing.If anyone one of these are missing, I don't believe you will get to 450 with a 91 tune. Run the highest octane available in your location. What size injectors are you using? Minimum would be 39lbs. I would run a 93 tune to put more timing over the 91 tune which translate into more power.

I am running a Saleen Series VI SC ,95mm maf, 39lb injectors and a 93 tune.Put down 450 rwhp on a Mustang Dyno. Run smaller pulleys and smaller injectors before this current setup and could only make around 365 rwhp.
 

Macman45

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I'm going to be doing a DOB kit this spring. I won't be forging the motor so I'm going to be limited to the 450 rwhp. Do I need to run the more expensive 91 octane that I'm currently running on my N/A tune? My gut says I should run higher octane but what's the science say on it. Opinions?

Wut. You should run high octane on the stock motor
 

07 Boss

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So, if you want to run 450RWHP, at least three things need to happen
you need air, fuel and timing.If anyone one of these are missing, I don't believe you will get to 450 with a 91 tune. Run the highest octane available in your location. What size injectors are you using? Minimum would be 39lbs. I would run a 93 tune to put more timing over the 91 tune which translate into more power.

I am running a Saleen Series VI SC ,95mm maf, 39lb injectors and a 93 tune.Put down 450 rwhp on a Mustang Dyno. Run smaller pulleys and smaller injectors before this current setup and could only make around 365 rwhp.

485rwhp on 91 and 11 lbs of boost. We were up just past 500 but turned it down for longevity. 32# or 34# injectors. I can’t remember.
 

Someguy

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I have 480-490rwhp at factory redline (520 if I set the rev limiter higher), running 91 octane tune on stock internals. I would never run any lower octane on a boosted engine. That's asking for disaster

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