[vinnie115]

i just ordered sct/x3 from bama, i dont no if i ordered this right, the 87 street tune i got 91octane, the performance tune on 93 octane and the race tune on 93octane is this right?

[me2dumb4college]

if ur using a tune, i wouldnt run anything but 93... i dont think its good to keep swapping between octanes

[BLUE91GT]

^^ Really why is that? There are guys switching tunes all the time depending on what they are doing. Ie racing, DD, and so forth. Please explain.

[blkfordsedan]

Originally Posted by vinnie115 the 87 street tune i got 91octane, the performance tune on 93 octane and the race tune on 93octane is this right?

Not exactly sure about the "87 street tune i got 91 octane" part.......

Anywho..............there is no right or wrong, it's whatever you want.
I agree that there is no point in getting the Race tune for anything but the highest octane you have available in your area. The Street and Performance tunes are where you can do some different things. Personally, I wouldn't get the Performance tune for the same octane as the Race tune. There is very little difference between the Performance & Race tunes and the Race tune is still very streetable. There would be very little point in running the Performance tune, i.e.- if your paying extra for premium fuel, you may as well just run the Race tune.

I got both the Street tune and the Performance tune for 87 octane, and the Race tune for 91 octane (highest in my area). This way, I can run the Street tune if I'm taking a road trip or concerned about maximum economy. I run the Performance tune 99% of the time, and since it's for 87 octane, I can put in whatever fuel I want and not have to worry about spark knock. In my area, 89 octane is 10% ethanol and is .10/gal cheaper. If I decide to splurge and pay .20/gal extra for 91 octane premium, then I can switch to the Race tune.

As for performance, the car runs WAY better on the Performance tune, even though it's only for 87 octane. No comparison at all to the factory tune. The 91 Race does have a little more power, but not a huge difference.

[mcqueen]

Originally Posted by me2dumb4college if ur using a tune, i wouldnt run anything but 93... i dont think its good to keep swapping between octanes

It's fine to swap between octanes. The only problem comes when switching to a higher octane. You just need to be sure that you fill up with the higher octane, run through a tank of it without the tune for it, than fill up with the higher octane again and upload the tune. Or you can run the tank damn near dry but then you run the risk of having to push your car to the gas station. Either way, mixing a higher and lower octane fuel will result in a fuel that has an octane somewhere between the two and running a lower octane than what you're tuned for can result in detonation (preignition) which is very harmful to the engine.

[Woodman]

Originally Posted by mcqueen It's fine to swap between octanes. The only problem comes when switching to a higher octane. You just need to be sure that you fill up with the higher octane, run through a tank of it without the tune for it, than fill up with the higher octane again and upload the tune. Or you can run the tank damn near dry but then you run the risk of having to push your car to the gas station. Either way, mixing a higher and lower octane fuel will result in a fuel that has an octane somewhere between the two and running a lower octane than what you're tuned for can result in detonation (preignition) which is very harmful to the engine.

Or you could buy a couple of gallons of race or AV gas to blend it up a bit. That gets a bit pricey though...

[blkfordsedan]

I would avoid AV gas in vehicle applications. If I decide to go from an 89 octane tune to a 91 octane tune, I just run until the "low fuel light" has been on for a few miles, then fill up with the higher octane. I then usually run until it gets down to 1/2 tank and refill with higher octane again before actually switching the tune. By that time, the fuel blend should be pretty darn close to the desired 91. I can also stop at one of the few stations that carry 92, just to help offset the mixing issue. That's also one of the reasons I opted for the 91 Race tune. It's a lot easier to get there from 89 octane.

I figure if I have 3 gal. @ 89 and add 12 gal. @ 91, I should end up with 15 gal. @ 90.6. If I then run half a tank and fill up with 91 again, I'll end up with about 90.8. So far, I haven't experienced any spark knock issues doing this. Obviously, if you're going from an 87 octane to a 93 Octane you got a lot more to go through. In that case, I would run at least 1 if not 2 full tanks of 93 before switching the tune. The same "3+12" fillup would only net 91.8 octane the first time, and even if you ran that tank down to 3 gallons and refilled with 12 gallons of 93 again, you should end up at about 92.76. That may not be close enough for the more aggressive calibrations of a 93 Race tune. I just like to err on the side of safety!

[AMChrisYoung]

Originally Posted by vinnie115 i just ordered sct/x3 from bama, i dont no if i ordered this right, the 87 street tune i got 91octane, the performance tune on 93 octane and the race tune on 93octane is this right?

OP, you can run any octane tunes you want, it's up to you. However, you just have to be careful when going up in octane(i.e. from your 91 tune to your 93 tune) that you have the correct octane fuel in the gas tank.

Posted below is some good advice regarding switching octanes.

Originally Posted by mcqueen It's fine to swap between octanes. The only problem comes when switching to a higher octane. You just need to be sure that you fill up with the higher octane, run through a tank of it without the tune for it, than fill up with the higher octane again and upload the tune. Or you can run the tank damn near dry but then you run the risk of having to push your car to the gas station. Either way, mixing a higher and lower octane fuel will result in a fuel that has an octane somewhere between the two and running a lower octane than what you're tuned for can result in detonation (preignition) which is very harmful to the engine.

[laoutlaw01]

I don't know about you guys but I just run 93 in my car at all times. If a few cents a gallon was going to bother me I would sell my stang and buy a feista!