A Symphony of Speed: The Art and Science of Engine Tuning DETROIT, April 3, 2001 - Spanish explorer Juan Ponce de Leon ventured into southern Florida in 1513 in search of the fabled Fountain of Youth. Oldsmobile racers will follow in his...
A Symphony of Speed: The Art and Science of Engine Tuning
DETROIT, April 3, 2001 - Spanish explorer Juan Ponce de Leon ventured into southern Florida in 1513 in search of the fabled Fountain of Youth. Oldsmobile racers will follow in his footsteps on April 6-8, 2001 - not in search of eternal youth, but in a quest for victory in the Grand Prix of Miami, the inaugural Indy Racing League Northern Light Series event at Homestead-Miami Speedway.
Just as Ponce de Leon's expedition was a journey into the unknown, IRL teams will be exploring uncharted territory in their Florida foray. The roller-coaster one-mile oval at Walt Disney World Speedway near Orlando has been replaced on the IRL schedule by the 1.5-mile superspeedway south of Miami. This new venue presents a formidable challenge not only for drivers, but also for the GM Racing engineers and independent builders who supply Oldsmobile IRL Aurora V8 engines to the majority of IRL teams.
All 1.5-mile ovals are not created equal. In contrast to the familiar high-banked speedways in Atlanta, Fort Worth, Texas, and Sparta, Ky., the Homestead-Miami track is virtually flat. With modest six-degree banking in the turns, this distinctive track design demands adjustments in both chassis setups and engine tuning by teams seeking a competitive advantage.
"The speeds in the corners will be significantly slower at Homestead than they are at Texas or Atlanta," explained Rick Long of Speedway Engine Development. "This means that we need to tune the engines to operate in a wide power band. On high-banked tracks, the engine speed seldom falls more than 800 rpm below the 10,700 rpm rev limit. At Homestead, however, we expect to see engine speeds change as much as 1,500 rpm between the turns and the straights."
Long speaks with authority. Oldsmobile IRL Aurora V8 engines prepared in his Indianapolis shop propelled Buddy Lazier to the 2000 IRL championship and won the last three IRL races. Speedway Engine Development is one of the most prolific builders in the open-wheel series, supplying Oldsmobile engines for Panther Racing (Sam Hornish Jr., driver), Hemelgarn Racing (Buddy Lazier and Stan Wattles), PDM Racing (Jeret Schroeder), Vertex-Cunningham Racing (Shigeaki Hattori), and Curb-Agajanian/Beck Motorsports (Billy Boat). Speedway also will supply Oldsmobile engines for Michael Andretti's return to the Indianapolis 500.
"The shape of the engine's power curve and how the power comes on is very important on a track like Homestead," Long said. "We widen the engine's rpm range by changing the diameter and length of the exhaust system and by adjusting the length of the inlet air horns. Lengthening the inlet air horns makes the power curve wider; shortening them makes the curve narrower."
A racing engine is often described as a finely tuned instrument, and that is an apt analogy. The vocabulary of competition conjures images of an orchestra, with intake "trumpets," air "horns" and "tuned" exhausts. In fact, an IRL Aurora V8's intake and exhaust systems work much like the tubes of a pipe organ. Just as changing the length of an organ pipe alters its pitch, adjustments to a racing engine's induction and exhaust systems change its performance characteristics.
This symphony of speed is played at a frantic pace. In an engine running at 10,000 rpm, it takes only 12/1000ths of a second for each cylinder to complete the four cycles (intake, compression, power, and exhaust) that constitute internal combustion. The rapid opening and closing of the valves, the rise and fall of the pistons, and the pulses inside the exhaust system produce pressure waves that are reflected through the entire system. Engineers and engine builders can harness these pressure waves to improve performance.
By "tuning" these waves that resonate though the engine, more fuel and air can be packed into the cylinders, thereby producing more power. Camshaft timing - the points at which the IRL Aurora V8's 32 titanium valves open and close - also plays a significant role in tuning. A naturally aspirated engine can be effectively "supercharged" to increase its output by carefully orchestrating the pull and push of the pressure waves that reverberate through the motor.
Just as in a complex musical score, timing is everything in a racing engine. Pressure waves that reach the cylinders out of sync can cause the engine to hit a sour note. Moreover, tuning that is effective at one rpm point may be off key at another. GM Racing, the technical arm of GM's worldwide motorsports program, provides technical assistance and specialized components to help builders tune their Oldsmobile engine packages for various tracks.
"A change as small as one-quarter of an inch in the length of the intake trumpet can move the peak horsepower several hundred rpm," commented GM Racing development engineer Dick Amacher. "The goal is to balance high-speed horsepower with mid-range torque to produce a wide, 'driver-friendly' power curve that suits the characteristics of a particular track."
Factors such as altitude also must be considered. "Homestead-Miami Speedway is close to sea level and has the lowest elevation of any track on the IRL circuit," Amacher continued. "Consequently, the barometric pressure will be relatively high, which enhances the performance of a naturally aspirated engine by providing a stronger 'push' to fill the cylinders. At a track like Pikes Peak International Raceway, which is a mile above sea level, the barometer is typically five inches lower, which reduces engine output substantially."
The same artful engine tuning that wins races on the Indy car circuit also makes driving on the highway a rewarding experience for Aurora owners. Like the racing engine it inspired, the production Aurora V8 engine has a tuned induction system that produces smooth, responsive power on demand.
Engine tuning is an important part of the repertoire of both GM engineers and Indy car engine builders. The symphony of speed they create is music to the ears of open-wheel racing fans.