There is no doubt in my mind I've been putting in 93 octane at various gas stations. To me at least, switching over to 100 octane was a very noticeable difference. I really don't think it's a placebo effect either.

That's my take on it at least.

 

A gasoline test in a UK car mag published a few years ago found that on the dyno and on the track race gas delivered noticeable gains in HP and torque. The test vehicle was a VW GTI with a turbo-charged engine (stock).

While the energy content of race gas vs. regular/premium gas is nearly the same (too little difference to make any difference) the one benefit is the DME can trigger the spark much earlier without incurring detonation.

This early spark gets the mixture burning sooner and develops more pressure so more force is pushing down on the piston and at the optimum time in the power stroke to convert chemical energy to mechanical energy.

I have never used 100 octane gasoline in my Turbo but I have run 93/94 octane in it and compared to the 91 octane I regularly use -- it is all I can get here in CA without resorting to filing up at the few and far between race gas pumps -- the engine was noticeably more responsive, quicker to gain revs.

Race gas can also be blended in such a way its burning is optimum at the higher RPMs race engines experience.

I do not have the Evo review handy to quote word for word from, but the comments about race gas (paraphrasing) was that while it was so so at low RPMs above a certain RPM threshold the engine just took off and the engine's performance compared to it being fueled with non-race gas, even the best of the non-race gas, was like night and day.

Around town race gas is of no value. All you really should do is run the proper octane of gas, or in the case of us that live/drive in areas where 93/94 octane is not available, run as close to 93/94 octane as possible, and buy a top tier fuel and from a busy station. These engines are tuned to run at the edge of detonation. As long as the right octane of fuel is used, the detonation will not appear and the DME can advance the spark timing to whatever it can to optimize engine performance. The DME has limits to how much it can advance the timing so running an octane of fuel above 93/94 will not gain any extra in this regard. (Bear in mind as engines age/wear their octane requirement can go up so a factory fresh engine may not need anything above 93 octane, but one with say 100K miles (just a number) might require 94 possibly more octane under some conditions, such as it would experience on the track.)

At the track I'd use race gas, but as others have mentioned only if it was safe to use in modern engine with O2 sensors and catalytic converter. If the race gas gets its high octane from lead, MTBE, or MMT or some other possibly harmful engine additive and not pardon the expression organically I would not use it.

And I would seek to have as little non-race gas in the tank as possible to maximize the benefits of race gas over and above its higher octane. At some point the higher octane is not going to bring anything more to the table, but the other characteristics of race gas are still worth the cost of admission.

 

Your car is tuned for a specific octane. Running anything over that octane in stock trim is just pissing money out the tailpipe.

 

+1

Frank C.

 

I've put 100 octane in my tank (the whole tank) from a local 76 station. Honestly, i can't feel any driving difference. I'm not a gearhead though so it's possible there is a difference and it's just lost on me. as somebody else posted, two dyny sessions is the only way to really know.

 

I'm still not a 100% why a comparative "dyno session" needs to be accomplished. Hasn't this subject been studied in excess? I've seen videos/literature stating higher octane improves HP, provided the engine management systems are able to take advantage of the higher octane. Primarily, economy vehicles won't. With all the talk about energy and the high point of the piston on its trajectory of execution in the chamber blah, blah, blah. No one has actually answered the OPs question. I know I read "...with my 66 VW engine..." Really? Seriously, really?

The question is: Is the Porsche 991 991 able to take advantage of higher octane fuels, above Porsche's minimum requirements. My very uneducated guess is yes. Did the OP sense an improved performance gain with higher octane? I believe so. My untechnical observation, Porsche has the foresight to build a system that adjusts for the variances in fuel octane. Some parts of the US, you can only get 91 octane. Some you can get 93. Some you can only get 90.

If one of you Porsche Engineers could answer the algorithm of piston detonation and its location of peak pressure on 93 vs 100 octane, we would appreciate it. Otherwise, you're making comparative guesses between Porsche engine management systems, your Chevy Camaro, 72 VW or some other vehicle in your signature, that no one cares about.

 

Save your $$$. The "Mythbusters" used a Dyno to compare 87, 89, 91 & 117 (C17racing fuel) in a high compression Suzuki R600. The results proved that 87 produced as much HP as the 117 octane fuel.

Consider using racing fuel for high temperature racing environments. It will provide some detonation margin but no more HP.

private

 

The question is does the Porsche adjust for higher octane? Most cars adjust downward if the octane is lower.

 

I find it hard to believe with all the different octanes and ethanol/non ethanol out there in the world where these cars are sold that the engine would perform the same with whatever you throw into it. Not buying it.

I've actually used the 100 octane unleaded and can vouch for the clear improvement I've experienced.

 

No, they do not. The design parameters are for 93 Octane and compression ratio is based on that. Just dumping in more octane without doing things such as increasing the compression ratio does nothing.

Also, there is no way in the world a butt dyno could feel a marginal increase, sorry guys. If I bumped your car up 5 HP you wouldn't even feel it. To actually notice a HP increase that you can tell - requires about 10 PERCENT increase of the engine. On a 991S that would be 40 HP - and you ain't a-gettin' that from a tank of gas.

Cute thread, though.

 

+1, there is no convincing those that wish to drink the K-Aid. Higher Octane fuel simply burns slower, it does not provide anything more than a slower burn in a NA engine to prevent detonation . I have flown airplanes for decades, we burn 100 leaded fuel. There was never a conversation about increased HP. It was all about avoiding detonation, which would destroy an engine in 15 seconds. Forum readers there is so much scientific information on this, just read.

Frank C.

 

I never made any quotes about octane adding on extreme horsepower and drinking K-Aid. I'll leave that to all your after market exhaust guys.

I merely have noticed that the engine is so much more responsive with no lag, hesitation, and just seems to just be firing right on point with the 100 octane. I would even argue the 0-60 time is improved. The engine actually sounds better too.

It's funny that I'm the only one who has used the gas and others are citing Mythbusters and a Suzuki crotch rocket as an argument against it.

 

I'm following this thread and have become convinced that there are some folks suffering from buyers' remorse including the shame of having a teen with WRX whip them coming off a red light.


One word: nitrous.

You want more energy in your fuel mixture without shelling out for a performance head and other stuff this is the answer. Of course it will shred the warranty, destroy the tranny and wipe out your tires but that kid with Subaru will be impressed

http://auto.howstuffworks.com/question259.htm

I

 

You should join the psychic friends network! Your ability to generalize and make things up is quite impressive! You could even get paid for it rather than ramble on here for no purpose at all. A lawyer I see? One step above a psychic.

I don't race teenagers on the street or anyone else. I merely was curious to try 100 octane for my own kicks and was quite surprised at the results. Nothing more, nothing less.

 

Maybe the increased performance you feel is caused by your regular filling station. Perhaps they are selling 87 octane as 91 or 93. You would notice an increase in performance in this case. The sensors would detect the difference and advance the timing over a period of time. I have checked various forums and can find no reference to the ECU mapping which would advance timing beyond the 93 octane setting. In fact, VR Tuned Performance (that has tuning software for the previous generation) speaks to this very issue. They indicate that they have to change the field mapping to recognize higher octane fuel as the ECU will not adjust above 93 octane.

I have used 100 octane fuel at the track twice on two different days when the temp and humidity were high in August at the Glen. I did so as a preventative measure (detonation) and felt no performance difference whatsoever, except maybe I was a little faster due to a lighter wallet.