Fuel question for GTPs

[BigfootKevin]

Will it harm the supercharged engine if i use regular(87 octane), or do i HAVE to use premium. I know if i use regular i wont get the peak performance side from using premium. But can it harm the engine in any way?

[Ripn12s]

I wouldnt go lower thean 89.

Ive been using 89 for 2 weeks now and Im rather heavily moded. I just dont beat on the car.

Using the lower rated fuel will cause more knock retard (KR) and when you pull KR you will lose timing and HP

[BigfootKevin]

ok, thanks. I only put in $10 of 87 in the other day and when it got low again, i put in 92. So i'd be fine with 89? I'll probably mainly be doing short drives to work, and rides on the highway.

thanks in advance

[BigfootKevin]

also, one more question. Do all gasolines give the same MPG? I don't know too much on fuel, so im curious. Will i get less MPG if i use Premium over Mid-grade?

[titleist312]

the L67 supercharged 3800 ive read is only8.5.1 compression hardly enough to be worrying about gas however i do suggest the best gas u can buy in your area also if your ecm or obd 2 has been modified definately use the best gas(highest octane rating). i love these guys that run race gas in their 13 second bracket cars , listen if you dont have the compression(10.5.1 or more) to support race gas your an idiot.

[GTP Jeff]

When you add boost to that 8.5-1 (static) compression ratio.. That can turn into an 11.0-1 (dynamic) compression ratio..

The book says..The supercharged GP with run just fine on 87 octane, but for best performance, use at least 91 octane..

As for gas mileage from fuel.. Providing you stay out of boost, so that the knock sensor doesn't take out timing.. I would think the best milage could be had on 87 octane.. The reason being that it will light off quicker, and generate more cylinder pressure for a given amount of fuel..

I read a test where they tested 104 octane unleaded race gas, back to back, with 93 octane unleaded.. In a 10-1 compression, big cammed, naturally asperated motor.. The 93 octane made 30 more horse power than the 104 octane race gas..

[Ripn12s]

Im sorry but 104 is all I use at the track.

Guess Im an idoit for getting rid of the 3 deg of kr that I see on pump gas

[kilroypr]

GTPJeff you are correct, the more octane a fuel has more heat is required to ignite. That is why that Jet Fuel and plane fuel octane rating is so high. So the gas can handle the engine temps and burns when it is supposed to burn.

Ripn12s, you are not idiot for using the correct fuel at the track. If you read GTP Jeff post if the car is driven normally without requiring boost a less octane fuel works but at the very moment boost is applied the Knocking and pinging would really harm your car. If you remember from the owners manual and waranty manuals if the dealer discover that internal engine worn parts are related to the use of not recomended octane fuel the waranty will be voided. So basically the octane rating depends on the application. I have never pumped 87 to any of my cars. Because the ingredients are so crapy that the car will start knocking on the smallest hills. And my GTP runs fine with 93octanes. Will not and will never try 87 on it. If you read the label on the fuel latch says premium fuel only

[kilroypr]

Bottom line if you are able to mix a gallon of racing fuel with 104octane you are using on the track you can really install a higher rating pulley(like the 2.8") without the intercooler because the fuel will ignite at the correct moment not before because you need a lot more heat to burn the higher octane fuel

[kilroypr]

what I meant was plane fuel

[Ripn12s]

You shouldnt be using avaition fuel in your car.

Believe me my car will react to bad/low octane fuel alot faster/worse then yours will

[kilroypr]

I know that, I never used aviation fuel, but, There was this guy that I have not seen in a while that really put almos 18psi on a honda civic and he was mixing aviation fuel with high octane fuel to handle the presure. I am not sure about the measures tought that he used so excuse the 1 gal thing. But that he made crazy stuff like that to handle the increased PSI's on the turbo, that was a fact.
I assume something really nasty happened to the honda cause I have not seen the guy for a long while now.

[kilroypr]

But makes sense based on your explanations for K&R causes using a lot higher octane fuel to get rid of KR and is cheaper for the time being than installing an intercooler.