Toluene as an Octane Enhancement

bdMember

Has anyone on this forum tried toluene as an octane boost? If so
a) what were the results,
b) where did you purchase the toluene
c) what ratio did you mix at
d) what was the octane of the base fuel used

Thanks in advance for the info provided.

11/19/1611:53 AM

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ehpanteraMember

Toluene has a RON octane rating of 121 and a MON rating of 107, leading to a (R+M)/2 rating of 114. (R+M)/2 are how ordinary fuels are rated in the US. Toluene has a sensitivity rating of 14 (RON: 121-107 MON). This compares favorably with alcohols, which have sensitivities in the 20 to 30 range. The more sensitive a fuel is the more its performance degrades under load. Toluene's low sensitivity means that it is an excellent fuel for a heavily loaded engine.

Toluene is denser than ordinary gasoline and contains more energy per unit volume. Thus combustion of toluene leads to more energy being liberated and thus more power generated. This is in contrast to oxygenated octane boosters like ethanol or Methyl Tertiary Butyl Ether (MTBE), which contain less energy per unit volume compared to gasoline. The higher heating value of toluene also means that the exhaust gases contain more kinetic energy, which in turn means that there is more energy to drive turbocharger vanes.

Toluene is such an effective anti knock fuel that it takes a smaller quantity to achieve the same octane boost compared to 100 octane racing gas.

Toluene is such an effective anti knock fuel it also means that it is more difficult to ignite at low temperatures. The Formula 1 cars that ran on 84 per cent toluene needed to have hot radiator air diverted to heat its fuel tank to 70oC to assist its vaporization. Thus too strong a concentration of toluene will lead to poor cold start and running characteristics. It’s recommended that the concentration of toluene used not to exceed 30 per cent or what the engine is capable of utilizing.

11/19/162:18 PM

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jd3Member

I've got a '71 911 with a hi compression AL head 327 SBC. Not sure what the CR is, but it detonates and overheats on pump 93 octane here near sea level.

It takes 2 gallons of toluene per tankful to stop detonation. 1 gallon of AV gas (or leaded race gas) stops detonation, and makes better power. The last time I bought toluene, the cost was similar to AV gas, so using AV gas in my situation is a no brainer.

If you want to buy toluene, the best price I found was buying 5 gal at a time at a big paint store.

Note that even "low lead" AV gas has a decent amount of lead in it, which really helps octane and lubricates valves. However, my car is carbureted, and lead would damage O2 sensors in an EFI application. Good luck.

Jack

P.S. The cheapest price I just found in an online search for 5 gal toluene is $10 a gallon. That is a lot higher than the ~$5 a gallon for 100LL AV gas right now.
Also note, what I wrote above is just my experience, with this car only, etc. YMMV.

11/19/162:34 PM

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kirkevansAmeriSport GT5-S builder Pantera Parts Vendor

quote:
Originally posted by ehpantera:
Toluene has a RON octane rating of 121 and a MON rating of 107, leading to a (R+M)/2 rating of 114. (R+M)/2 are how ordinary fuels are rated in the US. Toluene has a sensitivity rating of 14 (RON: 121-107 MON). This compares favorably with alcohols, which have sensitivities in the 20 to 30 range. The more sensitive a fuel is the more its performance degrades under load. Toluene's low sensitivity means that it is an excellent fuel for a heavily loaded engine.

Toluene is denser than ordinary gasoline and contains more energy per unit volume. Thus combustion of toluene leads to more energy being liberated and thus more power generated. This is in contrast to oxygenated octane boosters like ethanol or Methyl Tertiary Butyl Ether (MTBE), which contain less energy per unit volume compared to gasoline. The higher heating value of toluene also means that the exhaust gases contain more kinetic energy, which in turn means that there is more energy to drive turbocharger vanes.

Toluene is such an effective anti knock fuel that it takes a smaller quantity to achieve the same octane boost compared to 100 octane racing gas.

Toluene is such an effective anti knock fuel it also means that it is more difficult to ignite at low temperatures. The Formula 1 cars that ran on 84 per cent toluene needed to have hot radiator air diverted to heat its fuel tank to 70oC to assist its vaporization. Thus too strong a concentration of toluene will lead to poor cold start and running characteristics. It’s recommended that the concentration of toluene used not to exceed 30 per cent or what the engine is capable of utilizing.

Incredibly informative, thank you.

11/19/167:00 PM

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droldsmobileMember

Although I am unable to provide anywhere near the scientific level of expertise posted above, I do have some insight to add.
I have had two highly modified track cars (700 hp Porsche 997tt and a 950hp Viper), and in both cases I ran one gallon of Toluene and one gallon of Xylene per tank. I don't remember the exact calculation, but I remember it working out to boosting a tank of 93 octane to around 97 octane.
I always kept the cars tuned to 93, but since both cars were pushing their limits, I liked having the extra buffer for safety.
I bagged the Viper on the track for two years without an issue before selling it. The next owner blew it up two months later, street driving on 93 octane gas.

11/19/1611:14 PM

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jmm3Member

Toluene smells good.