CART: Texas Tea and the IC108E
30 September 1998
Each Mercedes-Benz Racing Engine is a Well-Oiled MachineMONTVALE, N.J. - If youre a car person, its probably a Saturday morning hands-on project. If youre not, its probably a lunch-hour hands-off chore. Either way, oil changes are a part of everyday life.
Oil changes are also a part of every CART FedEx Championship Series race weekend. All eight Mercedes-powered Champ Cars will get at least two during the Texaco Grand Prix of Houston, Oct. 2-4, to be sure that each IC108E engine is running smoothly.
"The lubrication system, which includes the oil and every part of the engine that stores, delivers and retrieves that oil, is one of the most fundamental and critical considerations in the design of a racing engine and car," said Paul Ray, vice president, Ilmor Engineering, the race engine design and manufacturing arm of Mercedes-Benz. "Everyone has a vague idea about the relationship of oil and engine, but, in racing, it touches every aspect of performance, reliability and driveability."
More Than Lubrication
Oils chief job is to serve as a lubricant. A lubricant is defined by Websters Collegiate Dictionary as, "A substance capable of reducing friction, heat, and wear when introduced as a film between solid surfaces." It bathes internal engine parts, providing a slick coating which facilitates the movement of one metal part past another, preventing localized welding, an unfortunate circumstance more commonly known as "seizing." But the story doesnt end there. "A properly formulated oil doesnt just act as a friction inhibitor," said Robert Pache, a research associate with Mobil Oil Corporation, the makers of Mobil 1, a synthetic oil used in Mercedes Formula One, CART and FIA GT Championship engines. "It acts as a coolant, absorbing heat and carrying it away. It cleans the engine by picking up any debris and keeping it in suspension until it can be filtered out. It helps seal the pistons and rings with the cylinder liners. It even neutralizes acids created during the combustion process." The best oil in the world, however, is only as good as the system that carries it through the engine.
Total Loss to Dry Sump
At the start of this century, oiling systems were very primitive, allowing oil to drip from a reservoir atop the engine down over the exposed reciprocating parts and out onto the ground. Environmental impact concerns aside, the biggest problem with these "Total Loss" or "Constant Loss" systems was inefficiency. The faster the engine ran, the more frictional heat was produced. More heat meant more oil was needed for cooling, but oil delivery was limited by the gravity-fed system. Thus, power output was restricted by the rate of oil flow.
The next step was a recirculating system in which the engine mechanicals and oiling system were sealed inside the block, and the reservoir (later known as the oil pan or sump) was relocated underneath the engine to catch the oil. As technology progressed, a pump was added to pressurize the entire system, force-feeding oil to the bearings and other places where it was needed most to reduce friction and heat. The increased oil flow resulted in improved system efficiency and fewer limitations on power output. This recirculating, or "Wet Sump," system, although greatly improved since its first introduction,continues to operate in nearly all passenger vehicles today.
Mercedes-Benzs latest update of this technology, called the Flexible Service System, electronically measures oil quality and, based on these measurements, alerts the driver when it is time for an oil change, safely extending maintenance intervals up to 20,000 miles.
"Wet Sump systems are reliable, affordable and relatively simple, so theyre perfect for street cars," said Ray. "But in racing applications, Wet Sump has two drawbacks. First, the crankshaft ends up striking the oil as it sloshes around inside the sump during braking and cornering. That contact causes drag on the crank and robs horsepower from the engine. Second, the oil pan adds height to the engine, which in a Champ Car must be as low as possible for aerodynamic efficiency and handling benefits."
In response to these problems, designers created the "Dry Sump" system. Removing the reservoir from the bottom of the engine and replacing it with a remote oil tank, the drag on the engine from the crankshaft striking the oil was eliminated and engine height was reduced. A series of scavenge pumps were employed to draw the oil out of the engine and return it to the tank via an oil cooler.
Although all Champ Car engines are oiled using Dry Sump lubrication, and have been for more than three decades, the design of the sump, the scavenge pumps and other parts of the system remain closely guarded secrets as the efficiency of the system is still a key factor in power output.
Despite how high-tech the IC108Es oiling system is, the Mobil 1 used in Mercedes-powered Champ Cars is nearly identical to the product you would use in your own car.
Make sure your weekend oil change is complete in time to catch the Mercedes-Benz Motorsport Team in action on the streets of Houston, live on ABC Sunday, Oct. 4 at 4 p.m. ET.
