Skylark-69
Active Member
- Joined
- Jan 7, 2004
Blend Your Own Race Gas? Not.
If you’re a regular reader of the VetteNet mail list or visitor to the techie boards on the Corvette Forum, you’ve heard of other do-it-yourself additives said to improve gasoline. Unfortunately, a lot of that is urban legend. The executive summary of "DIY race gas" is: mixing it can be dangerous. You sometimes loose performance. You don’t save money.
Some of these DIY additives are: aniline, benzene, toluene, xylene and propylene oxide. Forget the first two. Both are highly toxic. Aniline is absorbed through the skin and impairs your blood’s ability to carry oxygen. Handle aniline improperly and you die. Benzene is a carcinogen, so you’ll die after improperly handling it, too–it’ll just take longer. Their toxicity and that they are used in making drugs has aniline and benzene Federally-regulated and not available to the public.
The aromatic hydrocarbons ("aromatics"), toluene and xylene are octane improvers. Significant amounts of toluene and lesser amounts of xylene are already in pump and racing gasolines. Both are available from automotive paint suppliers. Both are mildly toxic. Work with them wearing chemical-resistant gloves and in a ventilated area. If there’s any question about ventilation, wear a respirator.
In California, law restricts aromatics to 30% of a gasoline blend. Elsewhere it may be as much as 40%. The effect additional toluene or xylene has on pump gas is unpredictable for two reasons: 1) the octane boosting ability of both is less effective on premium pump gases than on regular grade gas because of the aromatics premium gases already contain, 2) toluene and xylene have high octane ratings alone but lower octane when blended with other gasoline components.
Toluene and xylene have specific gravities higher than pump gas so the more of them you add, the leaner you need to calibrate the engine’s air/fuel ratio. Once you calibrate for toluene- or xylene-spiked, DIY racing gas; don’t go back to running conventional gasoline until you recalibrate to a richer mixture or you’ll be burning pistons.
"Adding more toluene," Tim Wusz told us, "will increase the octane numbers of the gasoline, but when you get above 45 or 50%, throttle response is poor and the flame speed is reduced to where increasing amounts of fuel are still burning as combustion gases are forced out the exhaust valve. Once that happens, power is lost, not gained." Image: author.
Both have less volatility, so engines burning gasolines laced with high concentrations can be more difficult to start when cold.
In addition to handling, mixing, calibration, drivability and performance problems associated with DIY race gas, it has a lousy business model, too. A late-model Corvette with a medium-boost, aftermarket supercharger kit at the drag races on a warm day might need 97.2-oct. to keep the engine out of detonation. Toluene, used as a blending component, is 103.5-oct. To make 10-gal. of 97.2-oct., DIY race gas (1:1, 91-oct. unleaded and toluene) costs $42.80. Do it with 91 and 100 unleaded gasolines, you mix 3:7 for $32.05. Because a 1:1 mix of toluene and pump gas costs you performance and throttle response due to slow burn speed; not only is DIY race gas a lot more expensive, but it won’t perform as well, either.
The economics of xylene are worse than toluene. Xylene from industrial sources is "mixed-isomer" and has less octane boosting ability than toluene and a higher unit cost. The higher octane, single isomer varieties of xylene, typically obtained through science and laboratory supply businesses, are obscenely expensive, upwards of $100 per gallon.
Misunderstanding surrounds propylene oxide. Common uses for it are pesticide and fumigant. While the EPA lists it only as a "probable carcinogen," ingesting propylene oxide will at least make you sick and can cause coma or death. Use care when handling it. Some racers are under the impression "P.O." is an octane booster, but it is not. It is an oxygenate that works like nitrous oxide but not as well. "It will improve performance," Wusz stated, "but the mixture must be richer to take advantage of that. PO is more effective than MTBE but less effective than nitrous. The downsides of PO are: 1) it attacks plastic and rubber parts in fuel systems and 2) its low, 95 deg. F boiling point gives it a tendency to easily escape from a blend leaving the DIY race gas blender with a gasoline which he thought contained a certain amount of PO, but in reality, may have retained far less of it. This makes tuning exceedingly difficult."
Bottom line: brewing your own race gas a foolish move for a lot of reasons. You’re better off buying it ready-made.
Info came from Tim Wusz.
If you’re a regular reader of the VetteNet mail list or visitor to the techie boards on the Corvette Forum, you’ve heard of other do-it-yourself additives said to improve gasoline. Unfortunately, a lot of that is urban legend. The executive summary of "DIY race gas" is: mixing it can be dangerous. You sometimes loose performance. You don’t save money.
Some of these DIY additives are: aniline, benzene, toluene, xylene and propylene oxide. Forget the first two. Both are highly toxic. Aniline is absorbed through the skin and impairs your blood’s ability to carry oxygen. Handle aniline improperly and you die. Benzene is a carcinogen, so you’ll die after improperly handling it, too–it’ll just take longer. Their toxicity and that they are used in making drugs has aniline and benzene Federally-regulated and not available to the public.
The aromatic hydrocarbons ("aromatics"), toluene and xylene are octane improvers. Significant amounts of toluene and lesser amounts of xylene are already in pump and racing gasolines. Both are available from automotive paint suppliers. Both are mildly toxic. Work with them wearing chemical-resistant gloves and in a ventilated area. If there’s any question about ventilation, wear a respirator.
In California, law restricts aromatics to 30% of a gasoline blend. Elsewhere it may be as much as 40%. The effect additional toluene or xylene has on pump gas is unpredictable for two reasons: 1) the octane boosting ability of both is less effective on premium pump gases than on regular grade gas because of the aromatics premium gases already contain, 2) toluene and xylene have high octane ratings alone but lower octane when blended with other gasoline components.
Toluene and xylene have specific gravities higher than pump gas so the more of them you add, the leaner you need to calibrate the engine’s air/fuel ratio. Once you calibrate for toluene- or xylene-spiked, DIY racing gas; don’t go back to running conventional gasoline until you recalibrate to a richer mixture or you’ll be burning pistons.
"Adding more toluene," Tim Wusz told us, "will increase the octane numbers of the gasoline, but when you get above 45 or 50%, throttle response is poor and the flame speed is reduced to where increasing amounts of fuel are still burning as combustion gases are forced out the exhaust valve. Once that happens, power is lost, not gained." Image: author.
Both have less volatility, so engines burning gasolines laced with high concentrations can be more difficult to start when cold.
In addition to handling, mixing, calibration, drivability and performance problems associated with DIY race gas, it has a lousy business model, too. A late-model Corvette with a medium-boost, aftermarket supercharger kit at the drag races on a warm day might need 97.2-oct. to keep the engine out of detonation. Toluene, used as a blending component, is 103.5-oct. To make 10-gal. of 97.2-oct., DIY race gas (1:1, 91-oct. unleaded and toluene) costs $42.80. Do it with 91 and 100 unleaded gasolines, you mix 3:7 for $32.05. Because a 1:1 mix of toluene and pump gas costs you performance and throttle response due to slow burn speed; not only is DIY race gas a lot more expensive, but it won’t perform as well, either.
The economics of xylene are worse than toluene. Xylene from industrial sources is "mixed-isomer" and has less octane boosting ability than toluene and a higher unit cost. The higher octane, single isomer varieties of xylene, typically obtained through science and laboratory supply businesses, are obscenely expensive, upwards of $100 per gallon.
Misunderstanding surrounds propylene oxide. Common uses for it are pesticide and fumigant. While the EPA lists it only as a "probable carcinogen," ingesting propylene oxide will at least make you sick and can cause coma or death. Use care when handling it. Some racers are under the impression "P.O." is an octane booster, but it is not. It is an oxygenate that works like nitrous oxide but not as well. "It will improve performance," Wusz stated, "but the mixture must be richer to take advantage of that. PO is more effective than MTBE but less effective than nitrous. The downsides of PO are: 1) it attacks plastic and rubber parts in fuel systems and 2) its low, 95 deg. F boiling point gives it a tendency to easily escape from a blend leaving the DIY race gas blender with a gasoline which he thought contained a certain amount of PO, but in reality, may have retained far less of it. This makes tuning exceedingly difficult."
Bottom line: brewing your own race gas a foolish move for a lot of reasons. You’re better off buying it ready-made.
Info came from Tim Wusz.
