Chevy Indy V8 insights: The alcohol alternative. KANSAS CITY, Kan., July 4, 2002 -- The 100-degree heat of a Midwestern summer may be stifling, but it pales in comparison to the four-digit temperatures that are commonplace inside the cylinders...
Chevy Indy V8 insights: The alcohol alternative.
KANSAS CITY, Kan., July 4, 2002 -- The 100-degree heat of a Midwestern summer may be stifling, but it pales in comparison to the four-digit temperatures that are commonplace inside the cylinders of Chevrolet's championship-winning Chevy Indy V8 racing engine. The forecast for this weekend's Ameristar Casino Indy 200 at Kansas Speedway calls for hot action on the track and hellish operating conditions for pistons, valves and other internal engine components.
It's said that motorsports runs on money, but in fact the fuel that powers the four-wheeled missiles of the Indy Racing League is methanol - a.k.a. "wood alcohol", a liquid that burns with an invisible flame. Unlike gasoline, which is refined from petroleum, methanol can be produced from natural gas, wood, coal, agricultural waste, and even urban trash. Because methanol is considered a renewable resource, it is a prime candidate as an alternative to fossil fuels. Thus the racetrack provides a laboratory for real-world experiments with this promising energy source.
Methanol became the fuel of choice for open-wheel racing in the '60s due to safety concerns. A methanol fire can be extinguished with water, while a gasoline fire requires special chemical extinguishers. Methanol's unique characteristics also make it an attractive choice for high-performance engines.
"The characteristics of methanol fuel influence the overall design of an Indy car engine," said Roger Allen, GM Racing's lead IRL engine designer. "Methanol allows a higher mechanical compression ratio than a comparable gasoline-burning engine, but it also requires an air-fuel mixture approximately twice as rich as gasoline to produce maximum power."
While gasoline is a complex brew of hydrocarbons, methanol is a relatively simple compound of carbon, hydrogen and oxygen: CH3OH. The chemistry of its combustion is straightforward. Two methanol molecules react with three oxygen molecules to produce carbon dioxide and water. This reaction also releases energy, which is what pushes the pistons, turns the wheels and ultimately propels an Indy car to more than 200 mph.
While gasoline requires atmospheric oxygen for combustion, methanol provides some of its own oxygen, nearly 50 percent by weight. Air/fuel mixtures that produce maximum power with methanol are much richer than gasoline mixtures -- approximately 5:1 for methanol vs. 13:1 for gas.
"The extremely rich air/fuel mixture used with methanol has consequences for both engine designers and for IRL teams," Allen explained. "The ports in the Chevy Indy V8's cylinder heads are sized to accommodate the high volume of fuel in the intake charge. Methanol produces more combustion products than gasoline, so the exhaust ports must be correspondingly sized to scavenge the burned gases from the cylinders. Under racing conditions, a methanol-burning IRL engine gets around two miles per gallon. The IRL rulebook limits the fuel load to 35 gallons, so the engine's thirst for fuel figures prominently in pit stop strategy."
Methanol's octane rating is typically 10 points higher than pump gasoline, which means it is less prone to detonation, the explosive self-ignition of fuel in the cylinders. Methanol will tolerate a higher compression ratio than pump gasoline, which improves engine efficiency. The Chevy Indy V8, for example, has a 15:1 compression ratio versus 9:1 in a typical street engine.
Methanol motors run relatively cool, a distinct advantage in a long, hot summer. Just as the alcohol in aftershave cools the skin when it evaporates, methanol cools the engine's intake tract when it vaporizes. This chilling effect helps to increase air density and boosts engine power.
"Methanol burns at a lower combustion temperature than gasoline, so the cooling system has less heat to dissipate," Allen noted. "This allows chassis designers to reduce the size of the radiators and cooling ducts, which in turn enhances an Indy car's aerodynamic performance."
So is methanol the perfect fuel? Unfortunately, methanol has drawbacks as well as advantages. It is corrosive to aluminum, magnesium and other metals commonly used in racing engines. Alcohol can also attack rubber and plastic materials in the fuel system. IRL teams routinely "pickle" their engines at the end of the day by running them on gasoline until the methanol is flushed from the fuel system. This protects against corrosion of the fine electric wires in the fuel injector solenoids. Like many other fuels, methanol is considered a hazardous material and is poisonous when swallowed or inhaled in high concentrations. These risks can be minimized by proper storage and handling.
General Motors has extensive experience with alcohol as a supplement or replacement for fossil fuel. For example, Chevrolet produced a fleet of Variable Fuel Vehicles for a demonstration project in California. These vehicles had a special fuel system that allowed methanol and gasoline to be combined in a single fuel tank with mixtures ranging from M85 (85 percent methanol and 15 percent unleaded gasoline) to 100 percent unleaded gas. Ethanol, an alcohol produced from fermentation of agricultural crops (and a familiar ingredient of alcoholic beverages) has been used extensively as an automotive fuel in Brazil. A mixture of gasoline and ethanol made from corn is marketed in the U.S. as "gasohol."
While it may be true that money is the fuel that powers auto racing, its is much simpler to refuel a IRL race car with methanol than with dollar bills.