Race gas 104 octane vs pump gas 92 (hp changes?)
09-10-2003, 07:39 PM
#1
Rennlist Member
Thread Starter
Race gas 104 octane vs pump gas 92 (hp changes?)
I know this has been gone over before, but everytime i ask a seemingly knowledgeble race team mechanic, I get a different answer. actually, most of the pro mechanics say that running higher octane in a porsche 928 S4 with over 10:1 compression, will increase HP. (even though there are no means for which fuel mixture or timing will change. (although some have hinted at it being somewhat adaptive) many have said to take the temp sensor in the wheelwell and put it toward some colder air as this tends to make the mixture richer. (and leave the altitude sensor alone as this could only hurt if play with indescriminately)
So, the reasons that some of these crew chief assessment of why the higher octane of 104 would help a stock 928 race car with only headers and fuel regs, is that even though the 92 octane fuel itself has greater energy potential than 104, it will burn faster yeilding more HP.
Has anyone done a dyno with race gas vs pump gas on a 928 or equivilant ECU set up?? any theory out there that may rule out the chance of increased hp with a higher octane gas.
I ran half race gas and half pump gas in the speed GT race, and, not only were my times much faster than ever with a 1:40.8 vs a previous best of 1:41.7 (however, this could be do to the level of competition and adrenaline) it kind of felt like the car was faster. (although my turn 11 right birm times to the start finish of 6.95 seconds was repeated with the race gas mixture. (for reference, Mark Anderson 475 rear wheel hp racer reaches this check point in under 6 seconds).
Any comments on this heavily discussed topic?
Mark Kibort
Speed GT #19
Porsche 928 S4 5 liter with headers and fuel regulator
320-330rear wheel hp. (depending on the gas??)
So, the reasons that some of these crew chief assessment of why the higher octane of 104 would help a stock 928 race car with only headers and fuel regs, is that even though the 92 octane fuel itself has greater energy potential than 104, it will burn faster yeilding more HP.
Has anyone done a dyno with race gas vs pump gas on a 928 or equivilant ECU set up?? any theory out there that may rule out the chance of increased hp with a higher octane gas.
I ran half race gas and half pump gas in the speed GT race, and, not only were my times much faster than ever with a 1:40.8 vs a previous best of 1:41.7 (however, this could be do to the level of competition and adrenaline) it kind of felt like the car was faster. (although my turn 11 right birm times to the start finish of 6.95 seconds was repeated with the race gas mixture. (for reference, Mark Anderson 475 rear wheel hp racer reaches this check point in under 6 seconds).
Any comments on this heavily discussed topic?
Mark Kibort
Speed GT #19
Porsche 928 S4 5 liter with headers and fuel regulator
320-330rear wheel hp. (depending on the gas??)
09-11-2003, 05:52 PM
#2
Drifting
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Re: Race gas 104 octane vs pump gas 92 (hp changes?)
Originally posted by mark kibort
I ran half race gas and half pump gas in the speed GT race, and, not only were my times much faster than ever with a 1:40.8 vs a previous best of 1:41.7 (however, this could be do to the level of competition and adrenaline)
I ran half race gas and half pump gas in the speed GT race, and, not only were my times much faster than ever with a 1:40.8 vs a previous best of 1:41.7 (however, this could be do to the level of competition and adrenaline)
Recently, I've run 2 Star Mazda Pro races, and I was amazed at my ability to go faster than I'd ever gone before due to the intensity of the competition (still not fast enough to run at the front
). Also, you should note that on an ALMS/World Challenge/Star Mazda weekend, you gain a lot of grip from the huge amounts of rubber that are laid down on the line as the week progresses!
09-11-2003, 07:42 PM
#3
Three Wheelin'
I am no mechanic, but knowledgable people have told me that with no timing changes, with only 10. to one compression ratio, any octane over 92 would go out the tailpipe. Ie- no increase in hp. The only way to find out for sure is to dyno, and make sure that all other peramiters (Thats probably spelled wrong) are the same. It would be a pain to do, and probably costly, but it's the only way to find out for sure. The rest of us would like to know the results.
Bill Seifert
944 Race Car
Bill Seifert
944 Race Car
09-11-2003, 07:49 PM
#4
Rennlist Member
Thread Starter
Re: Re: Race gas 104 octane vs pump gas 92 (hp changes?)
I know the adrenaline was pumping in this race, plus the car was set up better than all other previous races, and lighter.
However, I did run that 1:41.7 on the very first practice of the very first day, so not much rubber was layed down. And, most everyone, ran 1-2 seconds slower in the race vs their qualifying. I was only 5-6 seconds off the leaders laps, and was doing it with:
NO down force aids
100-200lbs more weight
100-150 less HP
stock original engine almost 20 years old
street sport supension, riding on the bump stops
12 heat cycle used tires
pump gas
euro highway street geared 4 speed with 5th overdrive (ie 2.2:1 rear end)
no real professional tuning suspension or engine.
I know there is a bunch of time here, I just wish I had only the HP to prove it!!!
mk
However, I did run that 1:41.7 on the very first practice of the very first day, so not much rubber was layed down. And, most everyone, ran 1-2 seconds slower in the race vs their qualifying. I was only 5-6 seconds off the leaders laps, and was doing it with:
NO down force aids
100-200lbs more weight
100-150 less HP
stock original engine almost 20 years old
street sport supension, riding on the bump stops
12 heat cycle used tires
pump gas
euro highway street geared 4 speed with 5th overdrive (ie 2.2:1 rear end)
no real professional tuning suspension or engine.
I know there is a bunch of time here, I just wish I had only the HP to prove it!!!
mk
Originally posted by Bryan Watts
I think part of it definitely has to do with the level of competition. When I first started racing, I ran into a wall in my ability to go faster until I moved to a more competitive class where I was having to push to keep up. All of the sudden, I busted through a plateau and took my driving to a different level in just 1 weekend.
Recently, I've run 2 Star Mazda Pro races, and I was amazed at my ability to go faster than I'd ever gone before due to the intensity of the competition (still not fast enough to run at the front). Also, you should note that on an ALMS/World Challenge/Star Mazda weekend, you gain a lot of grip from the huge amounts of rubber that are laid down on the line as the week progresses!
I think part of it definitely has to do with the level of competition. When I first started racing, I ran into a wall in my ability to go faster until I moved to a more competitive class where I was having to push to keep up. All of the sudden, I busted through a plateau and took my driving to a different level in just 1 weekend.
Recently, I've run 2 Star Mazda Pro races, and I was amazed at my ability to go faster than I'd ever gone before due to the intensity of the competition (still not fast enough to run at the front
). Also, you should note that on an ALMS/World Challenge/Star Mazda weekend, you gain a lot of grip from the huge amounts of rubber that are laid down on the line as the week progresses!
09-11-2003, 08:00 PM
#5
Race Director
Nope!
In a 944 spec car 2.5l 8V motor with about 10:1 CR it makes no hp difference. In fact even with 11:1 there is no HP difference.
Race gas only allows you to run a higher compression or more advance with out damaging your engine. It is the higher compression or advance that create the power not the octane.
Octane is purly the resistance to knocking that the fuel has and is not relatd to power content of the fuel.
The only exception to this is on newer cars with knock sensors. Some may retard engine timing if knocks are detected. This case the car will make less power than optimal. Therefore running a gas with an octane level that does not knock will ensure proper timming and full power. This is not really more power, but you are not LOSING power as the engine attempts to protect itself from detonation.
In a 944 spec car 2.5l 8V motor with about 10:1 CR it makes no hp difference. In fact even with 11:1 there is no HP difference.
Race gas only allows you to run a higher compression or more advance with out damaging your engine. It is the higher compression or advance that create the power not the octane.
Octane is purly the resistance to knocking that the fuel has and is not relatd to power content of the fuel.
The only exception to this is on newer cars with knock sensors. Some may retard engine timing if knocks are detected. This case the car will make less power than optimal. Therefore running a gas with an octane level that does not knock will ensure proper timming and full power. This is not really more power, but you are not LOSING power as the engine attempts to protect itself from detonation.
