hey guys, i recently discovered a 100 octane station by my house that sells it for a reasonable price. I currently use 91 octane but am willing to shell out the extra cash if it really makes my baby run stronger. so my question is, will it really make that much of a difference? I know it shouldnt harm my internals, but id appreciate some info from you guys, i did a search and couldnt really find a thread that gave me some concrete info.

my mods are s5 motor/turbo, downppipe(no cats) fmic, haltech e8 standalone, im running about 10-11 pounds of boost at about 255rwhp. Let me know guys im curious, thanks
-mitch

 

It won't make a bit of difference if you keep everything on your car the same.
Octane =/= power.

The higher octane fuel is more resistant to detonation, so it allows you to run higher boost and set your timing more aggressively.

 

alright cool beans, yeah i was gonna try to mess with the timing, but idk... Im pretty much maxin the boost on the stock turbo, so ill just give it a try

 

eh unless u know what your doing with the timing i wouldnt do that. just try bolt on things first

 

It will add additional safety to your current setup but it will cost you power unless you retune the timing.

post your timing map from the Haltech. I used to run 100 octane on my s4 T2. It ran 21psi fine on my T04S turbo.

 

it only makes more power if you are running more advanced timing than necessary or leaner air/fuel mixtures. only cars that are not properly tuned will have a noticable increase in performance with race fuel with one exception- >18PSI of boost it is a requirement or an aux. injection system.

 

higher octane rating increases the fuels resistance to ignite. if situation doesn't call for it(higher boost, more timing) you are wasting your money.

take things that nd_track_driver94 says with a grain of salt, he's a bit...un informed in the car world.

 

just running 100 octane will not magically make your car faster. the only way it will give you any extra power is if the car is tuned for 100 octane. you would just be wasting money.
that said, it will not hurt your car to run it, unless you are set up for ethanol or an alternative fuel.
if you road race your car then it can help as a safety barrier. you can mix the 100 with 93 pump and it will help agenst things like detonation, hot spots, because it burns cooler. i do this in my supra but only when at the track, i dont drive that hard on the street for that long. ( 5,000 - 8,000 rpm for an hour +)

 

Lets put it this way... the only way that 100 octane makes your car feel more peppy, more responsive, and better fuel milage, compared to 91 octane, without making any other changes, is if your timing is being retarded due to engine knock, when using 91 octane.

 

This topic comes up way too often. You guys summed up pretty well, but I'll say it again for good measure.

Octane # is just knock resistance. Higher octane just allows you to run more advanced timing / more boost safely. Timing/boost is where power can come from.

 

For that power level and boost on your setup, I would say "no". It's a waste of money. To reinforce what another poster has written, octane does not equal power. In fact, a lower octane fuel (everything else remaining the same) actually produces a more powerful torque stroke over a higher octane fuel. That being said however, sticking 100 octane fuel in will yield an enormous amount of reliability over 93 octane. You'd basically be able to beat the living crap out of your setup with little to no fear of it blowing up with a 100 octane race fuel.

B

 

Almost. While technically most higher octane race fuels do burn more slowly, that doesn't necessarily mean it's an excuse to crank ignition advance forward. The main reason to use a good, high-quality, high octane race fuel is for resistance to knock (your first point) with respect to using it in a hotter engine environment making double or triple the power of a stock engine setup. Think of it like the same rationale behind using a colder spark plug in a hotter engine environment. That is analogous to using a "colder fuel" in a "hotter engine" if that makes sense.

Screwing with spark advance isn't a terribly good idea unless you've got a lot of experience already having done with (with other fuels) while keeping in mind that it'll be quite easy to chunk a motor over it.

B

 

By definition, timing changes can increase combustion chamber temperature and pressure. Increased temperatures mean higher risk of knock, and higher octane fuels resist knock better due to the burn rate. You basically just said the same thing in a more in-depth way. I'm not advocating that everyone should go put race gas in their cars, then turn the CAS 10 degrees. Obviously correct tuning is essential.