91oct on an ecu for 93oct??

[davism1]

Is it fine to run 91octane even if the ecu is for 93. Its an apr stg 2 chip(v5 software)

[The_Jerbel]

Yeah, the ECU will adapt. You'll be fine.

[VZWalex]

youll be fine .. but if your in a area with hot weather .. I recommend using your 91 program ...... unless you want detonation .. trust me .. I know from experience.

[davism1]

Its not for me Im selling it but dont want to sell it to this guy if he cant use it. Thanks for the info guys.

[jibberjive]

I'm using a 93 program on 91. I've been trying to fill up with like 3 gallons/tank of either race fuel or E85 since a gas station a couple mins away sells both (I've heard people can run up to like 30% mixture of E85 with no adverse effects). I've also ran on pure 91 the past couple days and have been fine (though a little weaker). The only issue I've had was going WOT on a freeway onramp my throttle cut and I got a CEL. Haven't checked it yet, but the car was fine a couple seconds later.

[jibberjive]

Just an update, I went from running pure 91 on the 93 program for like 2 tanks, and just put in a couple ga of E85 for the last tank, and there's def a noticable difference in the power.

[S4 in_lowplaces]

The ECU your running is made to accept (adapt) up to 100 octane. the higher you go with octane the better the performance. Also, if you wanna run the 93 program with 91 gas, find a paint shop and get some toluene(octane booster).... I've seen other guys get some nice gains from it. Again, dont go over 30% of toluene mixed with gas, If you do you need to add ATF to the tank. GL guys

[McKennaS4]

its not hard or much more expenive to find an ecu tuned for 91 and sell you 93 program. your car will run better with the 91 chip without a doubt and it will save you the money of buying the higher octane fuel. (just to clarify i am not saying a 91chip on 91 is as good as a 93 chip on 93 but if 93 is not avail. i recommend getting an ecu tuned for 91) running a lower octane than the car is tuned for will cause your car to pull more timing because it is expecting to be running the higher octane fuel.. this will lead to a loss in performance. 91 to 93 is not a huge dif. but if you were to run 91 on a race file you would FEEL the loss in power without a doubt. like the jerbel said your ecu does adapt to the fuel you are using but it will never run as good as an ecu tuned to the correct fuel you're using.