KANSAS CITY, Kan., Thursday, July 5, 2001 - The chilly mornings and heavy jackets that were the trademarks of winter testing are distant memories now that the dog days of summer have descended on the Indy Racing circuit. The competition in the...
KANSAS CITY, Kan., Thursday, July 5, 2001 - The chilly mornings and heavy jackets that were the trademarks of winter testing are distant memories now that the dog days of summer have descended on the Indy Racing circuit. The competition in the Indy Racing Northern Light Series is heating up -- and so are the temperatures that the drivers, crews and engines must endure as they make their appointed rounds.
The inaugural Ameristar Casino Indy 200 at Kansas Speedway on July 8 will pit Oldsmobile's IRL Aurora V8 against a sizzling Midwestern summer. But even a 90-degree day in the heartland pales alongside the hellish temperatures that can be found inside an Indy car engine. The compressed gases in the cylinders can exceed 2,000 degrees Centigrade in a flash of combustion -- a temperature hot enough to melt metal. Managing this heat to prevent a meltdown is a top priority for GM Racing engineers and IRL engine builders.
"Cooling is always a trade-off in a race car," said GM Racing development engineer Dick Amacher. "You want to optimize the aerodynamics of the car by minimizing the airflow through the radiators while still protecting the engine with adequate cooling capacity."
An internal combustion engine harnesses the energy released by chemical reactions. The methanol fuel used by IRL race cars is synthesized from natural gas or coal -- the remains of prehistoric plants, plankton and protozoa. (Methanol is also a renewable fuel that can be made from wood byproducts, crops and even urban garbage.) Eons ago, these organisms banked the sun's energy in their cells. When this stored energy is harvested, it can propel a race car to 200 mph.
During combustion, methanol molecules break down into water and carbon dioxide, releasing energy -- lots of it. Every gallon of methanol contains 57,000 British Thermal Units (BTUs) of heating value, enough energy to raise the temperature of 570 pounds of water by 100 degrees.
Where does this energy go? Roughly 25 percent is converted to useful work, ten percent is used to overcome the engine's internal friction and five percent is radiated directly into the air. The largest portion, about 35 percent, goes out the tailpipes as exhaust heat. The remaining 25 percent is heat that must be dissipated by the engine's cooling system.
The heart of the IRL Aurora V8's cooling system is a gear-driven water pump that can move 100 gallons of coolant per minute -- enough water to fill a bathtub in 20 seconds. The lubrication system also cools the engine by carrying off heat from the pistons, bearings and other internal components. A typical Indy car oiling system uses 12 quarts of oil, or three times as much as a production car, and is responsible for approximately 25 percent of the engine cooling.
"Engine reliability is foremost," commented Andy Brown, engineer for the Pennzoil Panther Racing Oldsmobile Dallara driven by IRL points leader Sam Hornish Jr. "There is an aerodynamic penalty when you open up the radiator exits to get more air through the coolers. If you compare the sidepods in front of the rear wheels at Kansas Speedway with what we were running when the weather was cooler, you will see a big difference in the size of the openings. Opening the radiator exits reduces downforce, but the cooling requirements of the engine take priority."
Surprisingly, the engine is most vulnerable to overheating while running at low speeds during caution periods. "Indy cars do not have cooling fans, so we rely on the forward speed of the car to move air through the coolers," Brown explained. "When the car slows down during a yellow flag, the water and oil temperatures escalate. We try to keep the coolant temperature in the mid- to high-80s Centigrade (around 180 degrees Fahrenheit) when the car is at speed. Otherwise the temperature may get too high during cautions."
Like human athletes, racing engines are affected by hot weather. According to GM Racing engineers, a 10-degree increase in air temperature reduces engine output by approximately one percent because the heated air is less dense. An Oldsmobile IRL Aurora V8 that produces 650 horsepower on a crisp 60-degree autumn afternoon will lose approximately 20 horsepower when the thermometer hits 90 degrees.
Just as the alcohol in cologne and 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 restore engine power.
An Indy car driver has no such relief. Bundled in a multi-layer driving suit and surrounded by a carbon-fiber cockpit, the driver can only grin and bear the heat. "The driver gets paid enough to put up with it," Brown laughed. "Fortunately Sam is young and fit."
With seven victories in seven races, Oldsmobile has already put its fifth consecutive IRL Engine Manufacturer championship on ice. That won't stop Oldsmobile teams from turning up the heat in Kansas.