In most cases you would be 100% correct. Out here in Ca with our 91 octane horse ****, your are incorrect. As far as the Evo in concerned I mean. Check out what Shiv from Vishnu found on his dyno with a bone stock EVO. There is a little power to be found in this car with higher octane fuel. I don't think your going to get much higher octane with the off the shelf bosters. The ratio it would take to raise octane a couple of points is not reasonable. I do believe mixing about five gallons of 100 octane unleaded would be benificial. Is it cost effective? hell no. We are car guys though so money does burn holes in our pockets!

 

its cheap and it works, period!
http://www.need4speedpower.com/torco.html

 

if you haven't read "fuel selection" on pages 1-2 and 1-3 in your owners manual you should read it. it's somewhat interesting and related to this thread. i don't believe that higher octane adds powers because it doesn't. it only allows you to run higher boost. your ecu wants 94 and if it isn't getting it it starts to retard the ignition timing to avoid detonation. all i want is that when i fill the tank with supposed 94, and the gas man has ****ed me with a tank full of 87, is to get it up to a real 94 so the ecu doesn't pull my timing. another interesting note: the text books we used in aviation maintenance school called the numbers used for rating gasoline "anti-knock index" for 100 and lower, and "performance number" for 101 or higher. i think "anti-knock" is the best description for gasoline ratings.

 

Wow, that stuff looks good. Are you currently using it? What does the "seat of the pants dyno" tell you? Does your EVO seem to run better? THanks for the link and info!
John

 

I agree for the most part in what you posted. With the Dynoflash that was tuned for 94 octane on my car though, I would like to stay as close to 94 as I possibly could with the advent of the outlaw of MTBE and thus no more 94 in NY.

BTW, getting more than 50 miles to the tank with an octane booster could not have been a placebo effect. Maybe my car went haywire for that tank of gas?

Ken

 

I think all of the "respected" tuners agree that the Evo VIII runs on the thresh hold of detonation (and sometimes over it)... all the posts of people posting knock count confirms this. It is fact that higher octane fuel will do nothing for a car not tuned to take advantage of it... unless it is already suffering from any excessive knock (which apparently the Evo does on occasion).

 

no I havent used it. but people at the subaru forums did and they say it really works.

It isnt really necessary on stock cars, it will raise the octane too much. Unless you figure out a mix that will equal what you want.

But for the people who go drag racing or weekend street races who really want to up the boost, this is a good replacement to the costly racing gas.

 

At first when I read this post I was going to tell "the swami" to just say "NO" to drugs. But there is some merit to this. I did a little bit of looking into this myself.
I have two turbo cars now and wanted to know more about detonation. Because DETONATION is the killer for turbo cars. This will be old news to some, but new to others.

Here goes: Pre-detonation occurs when the the air/fuel mixture explodes prior to ignition from the spark plug. This is due to the fact that, lower octane fuel actually has a HIGHER flashpoint and ignites due to the heat/friction build up within the cylinder a split second before the spark plug fires. To remedy this you must use higher octane fuel which has a LOWER flashpoint. In which case eliminates the pre-detonation. As a result your car will run MUCH better & smoother, thus giving you the impression you are making monster HP with the higher octane.

 

for what its worth, octane booster is 5 dollars for 16 ounces and race gas is 5dollars for 128 ounces.

With that said, I doubt any car on this site running 19+ psi at high rpm gets zero knock on pump gas. High octane helps.

 

Octane ratings of 91 and 93 definitely affect the EVO. Just check the dyno runs by Shiv (or maybe Works). There is an 18hp difference in power on the same stock car.
When I had my car dyno'd, you could see where the ECU was pulling timing.
You may not be getting full detonation, but your ECU IS pulling time with lower octane. And for guys running higher boost, it's a must.
It REALLY sucks where I'm at. No gas above 91 octane for 175 miles!
I have run toluene and Zylene with good results, but it's not $3 a gal like I've seen posted; more like $9. I purchased a 5 gal can from Sherwin Williams for $40.
I add 2 gals to a full tank when I want to run it hard.

 

How bout using AVIATION FUEL? Alot of racers here use them.

 

Sure, I use 100LL...stands for low lead... when I can get it. Its dirst ****ing cheap at like 260 a gallon, but after 9/11 got a little harder to get. You hafta find a nice small airport and bring your own 5 gallon drum.

As for 91 vs 93....they should try running 76 brand 91, which uses ethanol instead of MTBE....MTBE breaks down and actually causes less octance in a combustion cycle then its rated at.

Also, was that 18 hp difference on the same dyno? On the same day? Otherwise, it doesn't mean much neways.

 

The only reason higher octane is more beficial is because they saw knock with 91. That agrees to what the other member posted. If your knocking, higher octane will not do **** for you unless you tune for it, either by leaning out or adding boost/timing.

 

The point is that every car on this site running 18+ psi to redline probably has some knock on any pumpgas, 91 or 94.

 

"Low Lead" is relative. AvGas is still chock full of lead, and running it for any extended period of time is going to foul your catalytic converter and give your O2 sensor an early death.

If you want to experiment with high octane gas without fouling things (AvGas), eating through fuel lines (xylene and toluene if abused), or wasting money on rice juice (octane "boosters") , I suggest you try some 100 octane unleaded or C16 race gas (some lead) at your local race track or performance shop. http://www.easternvp.com/fuels/

As commented elsewhere in here, unless you have tuning tools for leaning out your mixture or advancing timing, you'll get no benefit from higher octane. The exception is if your car is already getting timing pulled due to detonation (as can happen in Cali )