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My direct experiene is that I lose at least 40 rwhp due to timing retard if I run 91/92 octane vice 100 octane unleaded on the dyno.

A 50/50 mix of 100/91 octane gives me ~4 more mph trap speed at the strip, also. Consistently.
 

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What lagtime said.

You don't GAIN any power from using race gas, but you prevent timing retard, so your car will make alot more power with some race gas in the tank. I usually run 5 gallons of 104 at the track mixed with about 1-2 gallons of 93 leftover from the drive. Makes a HUGE difference in trap speeds, and the way the car feels.
 

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John,

I have not yet had a chance to read the links you provided (I'm killing a few spare moments at work :)) but there IS such a thing as too much octane if you are talking about, say 114 leaded in a BPU car.

Since higher octane gas resists burning better (it's a longer chain molecule as I understand it) you need to have enough ignition timing to take advantage of the slow burn time. Our stock ECU doesn't have enough timing advance to use more than 110, and I bet no BPU car can use more than 104 or so.

Since higher octane fuels have less energy, combined with not enough timing advance, that could cause a drop in power when compared to the *optimum* octane fuel for your particular motor.
 

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John,

What Chip said was right, but just to expand...

Higher octane gas is a more stable solution. Essientially, the more C-C bonds, the higher the octane rating. I'm sure you've heard the old addage that unless your car is high performance, 92 doesn't help. They're right...

Higher octane gas burns slower and more completely. (one reason why you'll see better gas mileage on race gas) However, that slower burn is a less violent burn which takes away from horsepower. So to answer your question, yes-- race gas makes less horsepower because of its slower burn.

However, it's that slower burn which makes the engine far safer to run. Since race gas is a much more stable solution, it is far less likely to spontaneously combust with high cylinder temps (detonate) or pre-ignite. Since it is harder for race gas to knock, modern cars like the Supra with knock sensors and DIS won't pull timing. The result is higher horsepower.

Of course, this begs the question is there such a thing as too much octane? Absolutely. The goal is to use the LEAST possible amount of octane without pre-igniting/detonating. That's where the HP/safety ratio is the best.

Clear as mud? :)
 
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Alright guys,

I just put in about 5 gallons of 114 leaded and fill up the rest of the tank with 93. NGK 3330's, RMM DP, Blitz exhaust and running about 14lbs. Was I hurting aything. The car seemed to run nice as hell, but wanted to make sure my baby was ok. Secondly since the gas is so damn expensive, and I'm not running that much boost, is this even worth it. Should I be using less than 5 gallons.

Thanks
Eddie
 

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Batosai said:
Alright guys,

I just put in about 5 gallons of 114 leaded and fill up the rest of the tank with 93. NGK 3330's, RMM DP, Blitz exhaust and running about 14lbs. Was I hurting aything. The car seemed to run nice as hell, but wanted to make sure my baby was ok. Secondly since the gas is so damn expensive, and I'm not running that much boost, is this even worth it. Should I be using less than 5 gallons.

Thanks
Eddie
Eddie,

You may really want to read my previous post for some insight here...

Your effective octane is about 96 considering that 114 is probably research rated and not (R+M)/2. Second, when you're on race gas, that's when you run it hard! If you weren't going to boost the car, buy 87 octane-- cheaper and more low level hp. For a BPU car on the street, 92 is almost always the proper choice. At the track, dyno, or street racing, 100 unleaded is your best bet to stop knocking and maximizing timing/horsepower.
 
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Thanks That's what I was thinking but just wanted to hear it from someone I guess in regards to my particular situation.

When I originally put in the 114 I was planning on pulling the wastegate hose but never really got around to it. So I guess a waste of gas/money.....oh well.
 

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gritsak said:
what about mixing the leaded race gas, with unleaded? what are the downsides to using leaded race gas? thats all we have around here
Downside to lead:

Screws up your O2 sensor. With leaded gas, some O2's last years, some go instantly. Simply depends how the lead adheres to the fillement in the sensor. If your car stumbles alot or doesn't run well at low RPMs/off throttle and you're running leaded frequently, replace the O2.

Will destroy the catalytic converter. When the lead sticks to the Pt, it stops the catalytic reaction from occuring. Running a downpipe? Then refer back to downside 1. :)

Of course I'm not running a cat... OR O2. Go figure :)
 
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I have a question....

would higher octan fuel make the car run cooler? =lower EGT?
 

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I would never run 87 octane in a TT Supra under any conditions. Dont our TT's require premium fuel? I use 93 or 94 octane pump gas for street driving and use 5 gallons of 115 octane mixed with 94 for the track.
 

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Zerosoul said:
I have a question....

would higher octan fuel make the car run cooler? =lower EGT?
In theory yes, but the difference is almost not noticeable. It's not that racegas is really a colder burn, it's just a longer burn. Again, it's advantage comes in higher temp stability.
 

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KJSUPRA said:
I would never run 87 octane in a TT Supra under any conditions. Dont our TT's require premium fuel? I use 93 or 94 octane pump gas for street driving and use 5 gallons of 115 octane mixed with 94 for the track.
I can see you've learned nothing from this thread. :(
 

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If you want to raise the octane of premium unleaded pump gas the best way to do so is with unleaded race fuel. Union 76 and VP both make unleaded formulations that have a R+M/2 octane of 100 to 104.

The race unleaded fuels mix in a predictable fashion with unleaded pump gas i.e.: 5 gallons of 91 mixed with 5 gallons of 100 would be 10 gallons of 95.5.

Check out these two links: http://www.osbornauto.com/blend.htm

http://www.osbornauto.com/dragster.htm

Leaded fuels do not mix in a predictable way with unleaded fuel, and normally you end up with less octane than what you expect. This is why guys like Mark Cooper advise adding high octane leaded to a nearly empty tank.

If you can get unleaded race fuel,it's the best way to go at the drags assuming you aren't running a monster single at 30 psi.

And the really high (110, 112, 114 & 118) octane numbers you see on some of the leaded fuels are Motor (not research) octane.
 

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AZWildcat said:


VP is the only company that rates this way...

UNOCAL and Sunoco give Formula Octane; Trick, Turbo Blue, and ERC give research.
That may be, and more credit to VP since motor is the relevant number where high performance cars are concerned.


Chip "Working hard to stay one step ahead (or at least even) of smart young guys like Dennis :)"
 
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