pcs

so what you are trying to say is that higher octane fuel will resist pre-ingintion better than lower octane fuel therefore allow you bump up your ingnition timing to give you a bit more power.

Daniel60

the only difference I get is better gas mileage with the high octane and tune. The low octane tune and gas gives me worse gas mileage. I have three different tunes 87,91,93 and the 91 actually does the best with the 93 octane gas for performance but not enough to really get $hittin about.

RickC37830

Surely you didn't mean that literally. A Ford Excursion doesn't weigh 10k lbs.

A WS6 has 325bhp and weighs 3494.3 lbs

Bluestar

I just had my Car inspected, did the whole change the CAI back to the Stocker bit, reflashed to stock....Passed the inspection. Then just for the heck of it I put the 87 tune in......just to see. About ten minutes later I flashed back to my 93 Tune, all is well now

Toad

There is no more power in high octane gasoline than in low octane. Octane has nothing to do with the energy that is contained in the fuel...it is a measurement of the detonation resistance. Check out this quote from an article in "European Car" magazine.

..."So what is octane? Without getting into chemistry, molecular bonding and hydrocarbon chains, octane is simply a measure of fuel-detonation resistance. The higher the number, the less prone the fuel is to detonation.
Detonation is the un-uniform ignition of the air/fuel charge in the combustion chamber. Normally, the combustion flame front originates from the spark center. When detonation occurs, the charge is lit at not only the spark center, but also from hot spots caused by build up from carbon deposits within the combustion chamber. This causes an uneven flame front, resulting in a sudden rise in combustion pressures, which can damage a piston on the power stroke.


A more catastrophic scenario, called pre-ignition, occurs when the charge unintentionally lights off without a spark. This usually means the event occurs toward the end of the compression stroke when charge temperatures and pressures are still rising. With pre-ignition, the sudden change in charger pressure from premature ignition as the piston is still moving up is equivalent to taking a hammer and beating it on top of your pistons. The sound is very similar, just like a ping.
Higher octane fuels are especially helpful to boosted or high-compression performance engines, along with older engines. With boost or a high-compression ratio, the air-fuel charge is compressed to higher pressures, which makes it more susceptible to detonation. Older engines with carbon deposits built up in the combustion chamber also benefit from high-octane fuels as the added space occupied by the deposits also effectively increases the compression ratio.


To avoid detonation, engines with knock sensors retard the spark timing at the onset of knock. Retarding spark timing or richening the air/fuel mixture to reduce knock ultimately robs power. This is why an increase in octane increases horsepower. Since the engine's knock threshold is effectively raised with higher octane fuels, spark timing is not retarded. This allows combustion and charge expansion to occur so that more force is put into the power stroke. Bottom line: Higher octane fuel only helps you make more power if your engine is at the verge of detonation (whether you know it or not)."


I tested three tunes, from Brenspeed, in my 2006 GT at the track. I used high quality 93 octane gasoline for all three tests. (I Know what you're thinking - no fair because the 93 octane gas gives the lower octane tunes better performance. Wrong. See the first line in the post. The only thing higher octane gas does is allow the TUNE to have a more advanced spark. So the TUNE is where you get the power. Dig?) There was less than 1/10th of a second difference between the tunes, and that is also the same amount of change in race times with each tune alone. Sorrym but the track I went to doesn't give receipts. Their machine is broken. I live in Puerto Rico, and that's just how it is here. But the times are accurate.

Brenspeed themselves have told me that the ONLY difference anyone should see between the different octane tunes is only to be had at WOT. Any other times the tunes are identical. So how can you be getting better fuel mileage? The way you drive your car has WAY more to do with miles per gallon than the tune or the octane.

So, the bottom line, for me, is there really is no difference in performance between gasoline octanes. If you have results, provable and uploadable, that higher octane gives you lower 1/4 mile times, I'd be delighted to see them. But I've looked all over this forum and cannot find any evidence that this is the case. The best most people can do is say they "feel it" in the seat of their pants. Sounds like hot air to me.

If you want to continue to spend, what, $5 more for every tank of gas for that special "seat of the pants" feeling you get, go right ahead. But I'm willing to bet that if you take your car to the track, and actually TEST the tunes, you'll find that your pants are lying to you.

zkiller

That is retarded, no pun intended. If you run lower octane fuel the car cant be tuned for maximum performance. PERIOD. Whether you are running forced induction or just fuel injection the ability to aggressivley tune the car is limited by the FUEL.
I run 25 degrees of timing advance in my racing tune. Try that with 91 octane and the car will have a vented block.
You think you can run 87 octane or 91 octane on a high compression engine , say 12-1 or 11.5-1 without a problem? Forced induction also creates extreme cylinder pressures like a high compression engine.
I have been around drag racing for 35 years and have seen them selling racing fuel there that whole time. I guess someone forget to tell them "there really is no difference in performance between gasoline octanes".

Toad

There is much more to racing fuel than the octane level my friend.

timothyrw

i think you've got your mind set so i don't hope to change it...

however, from insideline.com, regarding the new V8 in the hyundai's new flagship:

"At its core, the top-line Genesis is powered by an all-new, ultra-clean-running, DOHC 4.6-liter V8 that produces 375 horsepower at 6,500 rpm while running on premium fuel (or 368 hp with regular fuel). It produces 333 pound-feet of torque (324 lb-ft on regular fuel) at 4,500 rpm."

http://www.edmunds.com/insideline/do....photopanel..2.*

now, if less hp and torque (due to lower octane gas) doesn't produce worse track times... then up is down and left is right!