turbotsukuba

is there a real difference? if im tuned for 93 how bad would it be to put 91 in?

Stocker

It depends on what you mean by Tune. Most OEM computers these days will change timing in response to knock sensors telling the computer it's running bad. You lose power, maybe a lot. Aftermarket computers vary.

SR Tech

Canned tune or dyno tune? It'll probably be ok but to save 5-10cents is it really worth it?



If you have a logger/ data stream of some sort i'd just keep an eye on the knock retard deg if your actually going to run 91, that will tell you really quick if it will be ok.

majik

Don't do it. Ever. Not worth the risk.



If you put 91 in a 93 octane tuned Genesis Coupe, you may lose your engine.

SR Tech

That's Why I asked if it was canned. Theres a lot of areas that don't have 93, only 91 so the canned will be more conservative enough to run either without detonating. But then again I've never owned or tuned GC they may be more finicky

majik

They are, especially the 2.0T. Go WOT with 91 on a tune for 93 and ignore detonation occurring... you'll go boom.

Most tuners who offer 93 octane can also give a 91 option instead. If you find yourself in an area without 91, grab a decent can of octane booster and go easy on it til you can put some 93

Visionz

Def dont do it if you are tuned for 93. Buy a few bottles of octane booster like Majik said if you dont have 93 in your area. You'll seriously destroy your engine.

i8acobra

Actually, most bone stock imports (Korean, Japanese and Euro) are tuned for 93 from the factory. Here in Vegas (and in Cali), many imports don't make their advertised power because we're forced to run 91 octane. About twice a month I get 370Z's at the dealership with the customer complaining about detonation. I then have to explain to them that they have three choices... add a few gallons of 100 octane to every tank, run 91 an live with the detonation and reduced power, or I can use my Consult computer to dial back their base timing 2 degrees to eliminate the detonation. This, of course, results in about a 20 hp loss. So, yes, there's a difference.

Tom@TunerGoods

A lot of modern cars are tuned to handle various octane levels with 87 being the lowest. When the ECU/PCM notices a low octane condition, it switches to a more conservative map and consequently reduces the amount of power your motor will produce. That said, if you're using a mail order tune that is designed for 93 octane then you may want to consider contacting the mail order tune service you're working with and see if they can provide you with an updated map for 91 octane. Otherwise you could experience less than desired issues. Not necessarily engine destroying issues, but issues regardless.



Most importantly, don't ever stray from an octane specific tune (custom tune) with a turbocharged vehicle or you may very well be purchasing a new motor.