Sorry, I disagree. P 107 of the 993 manual: "Your engine is designed to provide optimum performance and fuel economy using unleaded premium fuel with an octane rating of 98 RON (93 CLC or AKI)."

From Steve W: "Racing gasolines have been widely accepted now as the main solution for maintaining peak performance in Porsches used for DE events and competition". He adds some interesting comments about the ethanol and MTBE not used in racing gas to increase octane.

While the ECU will adjust for as little as 90 octane, we would just like to add some 100 to get to the 93 recommended by Porsche. Sure, the ECU will adjust down from 93 to 90, but it will likewise adjust up from the rotgut pump 91 to 93.

I have felt it in the butt-o-meter.

 

Steve W: "Be absolutely certain that the racing gasoline that you may use is UNLEADED. Do not use leaded racing gasoline in any car with a catalytic converter, even for track use."

 

But I've not seen in YEARS any of the major brands NOT being unleaded, like Sunoco, Union, VP, ERC.........

 

I'd have to go dig up my data sheets, but when Laguna had their pump problems one race and we all had to use 91 from out on the highway if you didn't bring your own......there were even some lap records set.

I've run 91, 93 blend, 95 blend, you name it in the RSA over the years, never see an appreciable difference at the end of the straight at Thunderhill. Lap times are always pretty consistent. Either of them are 100% stock, down to still having the cat on. The ex-Kim 993? Well, that engine is waaaaaay to valuable to screw around with, so I'm pretty rigid on keeping a 95 blend in it.

 

Read my post again. I said "Having a higher octane than required..." and 93 is what is required by Porsche for a stock car. Under normal circumstances, putting 100 in a stock car will not make it perform any better than using the 93 it is was designed for. Read these: LINK LINK LINK LINK LINK
While these were mostly written for people who put premium in a car designed for 87, the same principles still apply... Using a higher octane that an engine is designed for will not normally help.

 

Jeff,

You are correct that 100 octane will not help NA 993s in general. I believe the only application is in track/race conditions for turbo engines. The 100 octane gas will ensure there is NO detonation issues in the turbo engines no matter what the ambient temps are. I believe 100 octane actually burns cooler (need to verify that).

However, Terry is also correct. Speaking to Ruf and others, they all reminded me that our ECU is tuned for optimal performance using 93-95 octane gas. We in CA suffers from crappy gas because of local environmental restrictions, so CA 911s do not perform as good as they can be. In fact Ruf told me to accept 10% lower HP in my BTR once it hits CA. So in that sense, now having 93 octane available, 1/2 miles from my house, is a true blessing.

I do not track my Ruf much, so the 100 octane is more for mental gratification than real world performance. It's fun to talk about once in a while. I won't use it often. The 93 octane stuff is too costly as is.

CP

 

Where is this stuff in SoCal??

 

I am just trying to get from 91 to 93. I have only done it once in 10 years, so I don't want to give the impression I am filling up with straight 100 every time for my daily driving.

 

Pong,

I would agree that adding 100 for a track session is cheap insurance for you turbo guys, but unless you are getting knocking due to extreme temps or something else and the ECU is retarding your timing as a result, the higher octane will not allow your car to make any more power than the 93, although maybe your RUF has different requirements. Generally, Higher octane gas is harder to ignite and slower to burn and unless your engine is designed for it, the car will not make more power because of it. In fact, it might even make less power, although probably not enough less to actually feel. Now, for guys that are running more advanced timing and/or have higher compression motors or are running higher boost, the 100 may be required for their engines to realize their full potential. There are exceptions to every rule, and I don't want to get in to a pissing match with anyone, but I was just trying to point out the common misconceptions about the benefits of using a higher octane rating than required under normal circumstances.

 

No worries Terry. I agree, 93 is the way to go if and when you can find it.

 

All I am trying to achieve is 93 as well. 5 gallons of 100, the balance of 91 gets me close.

 

When referring to octane, please make sure you are talking about Research octane or Motor octane or R+M/2 (US pump). VP lists RON and MON on their spec sheets/website.

I buy 33 gal drums (easier to move by yourself compared to 55 gallon drums)of VP fuel for my son's racing karts. His Rotax FR125 runs VP MS93 (unleaded), which IIRC is the spec fuel for the Star Mazda series.

As previously mentioned, VP makes LEADED and UNLEADED fuels, make sure you check the VP website to verify exactly what you're putting in.

The use of VP fuels has a side benefit, no ethanol added, so it's a bit safer to put into a car that will be stored (winter storage, etc). Of course the lack of ethanol will provide a slight increase in performance as well.