Maximum octane?
Thread Starter
Instructor
Joined: Feb 2005
Posts: 209
Likes: 17
From: Hillsborough, CA
Maximum octane?
Just curious - has anyone ever run race fuel in a stock 997 engine?
I know that the last thing you want is unburned fuel running through your exhaust, and running an engine rich is not good. Nonetheless, the computer controlled fuel system must have some octane latitude designed into it.
I was traveling through Atlanta, Georgia this summer and noticed that you can purchase 100 octane "race" fuel at some gas stations - which got me wondering. Enquiring minds want to know!
I know that the last thing you want is unburned fuel running through your exhaust, and running an engine rich is not good. Nonetheless, the computer controlled fuel system must have some octane latitude designed into it.
I was traveling through Atlanta, Georgia this summer and noticed that you can purchase 100 octane "race" fuel at some gas stations - which got me wondering. Enquiring minds want to know!
Race Director
Joined: Mar 2006
Posts: 15,362
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From: Tampa
This octane question came up at the Porsche Sport Driving School I attended and Hurley Haywood and a few other teachers commented on it saying that 95+ octane would produce negilgable gains in a stock 997S engine. So me always wanting to try this out I put some 100 octane in my 997S during a Sebring DE. I could not notice any positive effects on my lap times.
Rennlist Member
Joined: Nov 2001
Posts: 1,286
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From: CA
The engines are set up to run 93 octane. Anything above 94-95 is a waste of money. Very high octane will actually reduce power unless the engine management system is tweaked to take advantage of it.
You can buy 100 octane unleaded at the Unocal station on hwy 84 (Woodside Rd.) between hwy 280 and hwy 101. If you want optimal performance, blend about 4 gallons of that with 12 gallons of our California "premium" 91 octane. That'll give you a 93.25 octane blend
MC
You can buy 100 octane unleaded at the Unocal station on hwy 84 (Woodside Rd.) between hwy 280 and hwy 101. If you want optimal performance, blend about 4 gallons of that with 12 gallons of our California "premium" 91 octane. That'll give you a 93.25 octane blend
MC
Race Car
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Advanced
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From: Orange County, CA, USA
Rancho Santa Fe (near Encinitas off I-5)
VP Racing fuels
6089 La Flecha 858-756-2929
VP racing fuel 100 octane at the pump @ 6.99 a gallon (4/18/2007)
http://harmanmotive.com/raceGas.html
VP Racing fuels
6089 La Flecha 858-756-2929
VP racing fuel 100 octane at the pump @ 6.99 a gallon (4/18/2007)
http://harmanmotive.com/raceGas.html
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Pro
Joined: Nov 2006
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From: SAN CARLOS, CALIFORNIA
Hi,
I used a whole tank of gas at Luguna so I put in
7 gallons of 100 octane racing gas. I went .6 secounds
quicker but that might be because I had somebody
to chase. I know that the gas will burn off the carbon
on the top of the pistons. They had 110 octane gas
at the track but I am not that crazy.
Paul
I used a whole tank of gas at Luguna so I put in
7 gallons of 100 octane racing gas. I went .6 secounds
quicker but that might be because I had somebody
to chase. I know that the gas will burn off the carbon
on the top of the pistons. They had 110 octane gas
at the track but I am not that crazy.
Paul
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Racer
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From: jersey shore
my point is though that I never noticed any change whatsoever in performance when it was 92 or 93 or 94 for that matter.
Oddly I did once use BP's Amoco supreme 93 and thought it did run a bit better. This was the exclusive gas my dad would use in his new Cadillac during my childhood and he swears by it to avoid knock.
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I have an interesting note on this and on the CA guys who use 91 and say it stinks. I'm in NJ where we always have 93 and 94 octane (sunoco). I was filling at one particular station for months getting 93 octane - at some point during this time they switched to 92 octane but kept calling it "super" so I didn't notice the 1 point drop for a while. I then went to a new station for 93 thereafter.
my point is though that I never noticed any change whatsoever in performance when it was 92 or 93 or 94 for that matter.
Oddly I did once use BP's Amoco supreme 93 and thought it did run a bit better. This was the exclusive gas my dad would use in his new Cadillac during my childhood and he swears by it to avoid knock.
my point is though that I never noticed any change whatsoever in performance when it was 92 or 93 or 94 for that matter.
Oddly I did once use BP's Amoco supreme 93 and thought it did run a bit better. This was the exclusive gas my dad would use in his new Cadillac during my childhood and he swears by it to avoid knock.
) loved the Amoco Gold.
Racer
Joined: Nov 2006
Posts: 360
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From: jersey shore
The difference in performance would be hard to tell by the seat of the pants method as lets say going from 91 -93 gave us 5 hp, I doubt any of us would be able to notice it. I cannot seem to avoid that split second knock I mentioned even w/93, but I believe Edgy mentioned when he added octane booster it went away. BP/Amoco was the only clear (as in color) premium fuel and could still be; back in the day, my older Brother (rest his sole ) loved the Amoco Gold.
) loved the Amoco Gold.
Rennlist Member
Joined: Nov 2001
Posts: 1,286
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From: CA
Here is an excerpt from Wikipedia:
The power output of an engine depends on the energy content of its fuel, and this bears no simple relationship to the octane rating. A common understanding that may apply in only limited circumstances amongst petrol consumers is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption; this may be false under most conditions — while engines perform best when using fuel with the octane rating for which they were designed and any increase in performance by using a fuel with a different octane rating is minimal or even imaginary, unless there are carbon hotspots, fuel injector clogging or other conditions that may cause a lean situation that can cause knocking that are more common in high mileage vehicles, which would cause modern cars to retard timing thus leading to a loss of both responsiveness and fuel economy. This also does not apply to turbocharged vehicles, which may be allowed to run greater advance in certain circumstances due to external temperatures.
and the link to the site with a very good description: http://en.wikipedia.org/wiki/Octane_rating
Here is an excellent article with a test of octane boosters that provides a wealth of information on this subject:
http://www.europeancarweb.com/tech/0...ted/index.html
Cheers,
MC
Last edited by H20NOO; Dec 22, 2007 at 12:08 PM.
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Blending 100 octane and 91 octane = big improvement
Hello Group-
I have been doing a roughly 50/50 blend of 100 Torco and 91 Chevron or Unocal. This mixed at the Unocal station in Woodside, Bay Area, CA. $5.35/gal.
This yields about 95 octane RON.
I can say without a doubt my 2007 C4S runs significantly better - punchier, more responsive. Better acceleration.
It is also noteworthy that the insides of my exhaust tips are now honey brown vs. black., especially in terms that this is a street car, my daily driver. I have 9200 miles mixed freeway, canyon and traffic since June*
I propose that raising the octane to a min. of 93 and dilution of the lousy gas we get here in Cali can yield significant engine running benefits..........
I have been doing a roughly 50/50 blend of 100 Torco and 91 Chevron or Unocal. This mixed at the Unocal station in Woodside, Bay Area, CA. $5.35/gal.
This yields about 95 octane RON.
I can say without a doubt my 2007 C4S runs significantly better - punchier, more responsive. Better acceleration.
It is also noteworthy that the insides of my exhaust tips are now honey brown vs. black., especially in terms that this is a street car, my daily driver. I have 9200 miles mixed freeway, canyon and traffic since June*
I propose that raising the octane to a min. of 93 and dilution of the lousy gas we get here in Cali can yield significant engine running benefits..........
