Mustang Tuned for 91 Octane / Will 89 Octane Hurt????

Manewaymja2 · Oct 12, 2009

Hey there guys, my 1989 Mustang Gt is running a SCT Tune that was tuned for 91 Octane and here at our Pumps we get anywhere from 89 Octane to say 91 Octane (From Esso and Texaco) but you can never be 100% sure. So my question is if the gas i get was to say be a batch of 89 Octane would this hurt my cars tune or damage anything?

Please i have been googleing this allot with no help.

Also would adding a bit of 116 octane fuel be the way to go to safe guard this issue (15 gallon tank, say 3/4 Pump gas 1/4 Race Fuel).

Manewaymja2 · Oct 13, 2009

Is there anyone in here running a Supercharged Tuned Car????????????

tannerc91gt · Oct 13, 2009

It's not nessisarily going to physically hurt anything but you'll notice a drop in power as it's tuned for a higher octane. I guess you could use an octane booster if absolutely nessisary. Not sure what your saying about 89-91 being the same, as it should be 2 different pumps

90lxcoupe · Oct 13, 2009

running race gas is gonna actually make the car run worse if the car isnt set up to run on it.

If your that worried about it, put a wideband on the car so you can watch how its acting, or take some timing out

Mustang5L5 · Oct 13, 2009

I wouldn't do it.

5.0's don't have a knock retard sensor. Detonation in a power adder car can be deadly to the engine.

If it was tuned for 91octane, i would run 93octane.

If you have trouble finding 91, you should retune for 89. You really need a safety factor here

Manewaymja2 · Oct 13, 2009

OK let me clear up the Gas Octane / Pump issue. See we dont get any paticular octane gas here in the Bahamas. A freind of mine that owns a Texaco told me that ESSO & Texaco gets Gas that the Octane will vary from load to load, somtimes 89 others 91 etc.

Next would say adding 3 gallons of race fuel (116 Octane) to say 12 Gallons of Pump Gas (89-91 Octane) put me on the safer side of having 91 Octane or Higher?

My Tuner told me the same thing about taking out 2* of timing to be safe but i dont want to slow down any as the car has 393 WHP, trying to stay in the low 7's in the 1/8th. Will removing time hurt my HP Levels?

Thanks Guys
Matt

4eyegt · Oct 14, 2009

Not sure about a 5.0 with power adder but I run a 4cyl with turbo and full stand alone EMS. I'm set to run 91 octane and run a 50/50 mix of 91 and 100 to keep it safe. I busted a ring land on the old setup running too much boost/timing not enough fuel when the wastegate vacuum line came off and I spiked to 23#. Only took a second. Damage was done before I knew what happened.

You may lose a couple hp by pulling some timing but it will more then make up for it by saving you a motor. Also 116 is leaded gas right? If so O2 sensors hate leaded gas. You can run wideband with leaded gas but be prepared to stock sensors since leaded full is very hard on them.

90lxcoupe · Oct 14, 2009

Put a wideband on it and see what its really doing, and if you see the car going lean, then take timing out, running race gas is only gonna cause more problems. I dont think that your car will detonate if you run 89 instead of 91, if it does then i would suggest finding a new tuner because he has it right on the ragged edge of detonation.

All pump gas has its irregularites, and a good dyno tuner knows that he has to be really safe with the tune up because not every pump is the same, and who's to say that one station isnt putting 87 where the 93 should be

Mustang Tuned for 91 Octane / Will 89 Octane Hurt????

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