My question is will I see a big performance difference only running 91 octane when the car is tuned on 93?

my mods are,

intake
TBE
Tune

Car is an 2003 Evo 8.

 

Around 20hp loss on stock turbo.

 

you could lower your boost just a tad just in case if youre worried

 

If its a real aggressive tune you may want to stay of the gas a bit, 91 is obviously much more unstable than 93. Is it a temporary or permanent change?

 

Depending on how much boost you're running now I would definitely get a re tune for safety. An aggressive tune on 91 is asking for knock induced engine failure. I used Mellon Tuning for an email tune and it worked out well but I certainly lost a lot more than 20 whp from the aggressive 93 octane tune the car had before. But my motor is safe now. Given your location I'd also suggest English Racing. They seem to make some amazing numbers on the 92 octane they have out there.

91 is big hit in performance for these cars due to lack of knock suppression. Just look at some of the dyno graphs from the Cali people on here. Mod for mod they're making way less than those that run 93. Do you have E85 available? That's the money fuel. If not look into an Aquamist meth kit.

 

i was wondering about this too when i have to drive my car to different states...

 

I have a question on this. If he were to tune it for 91, would he be able to reclaim any or all of the lost power?

 

He would have a bit less hp obviously since your tuning between the difference of 91 and 93 octane. The difference would be is that he could drive it safely since its tuned on what hes using.

 

What Drop24 Said..If you are gonna smash on it..You are looking for knock..just keep an out for it or do a quick log for the car and see what you get..Otherwise get a 91 tune..my .02

 

thanks for all the help. I found a gas station nearby that sells 93, so that is what I will use from now one. more power is better :]

 

Possibly...depending on how aggressive your timing table is you might encounter knock and the ecu will start to pull timing which will cause you to lose power.

 

Get a tune for both if you can just in case. If you ever go on a trip like you mentioned and they don't have 93 available you are going to have to run 93.

 

I'm in the same situation.. I just got to Cali and there's no 93 anywhere.

 

Me2. Just moved to Colorado and they only have 91. Switching to E-85 in the near future though. I'm just staying out of boost and keeping the car in the cruising portion of the map which really never gets altered until I get a new tune.

 

Good as long as you don't WOT.