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Pickled Engines?
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Preserving Mercedes-Benz IC108D engines

MONTVALE, N.J. (July 8, 1997) — It's true. Pickles play an important part in big-time auto racing.

The preservative method that produces those tangy snacks is very similar to a treatment that helps make the Mercedes-Benz IC108D engine a winner on the PPG CART World Series circuit. The series, which features seven drivers (and all three Canadians) powered by Mercedes-Benz racing engines, visits Toronto for the Molson Indy, July 20.

Pickled Power and Cheese!?

"We started pickling the engines in about 1989, when we started using electronic fuel injection," said Franz Weis, of VDS Racing, an engine builder with nearly two decades of Indy car racing experience. Weis and VDS assemble and maintain engines for four Mercedes-powered teams on the CART trail. "Prior to that time we didn't bother preserving the engines, but it was just kind of common sense to start because we knew how corrosive the methanol (the alcohol-based fuel used by Indy car engines) was, and we knew how sensitive the injectors were."

Although methanol is a clean-burning fuel, if left in an idle race engine, it can leave a sticky mess. After an Indy car engine is run and then left to sit for a few days, there develops a white, gooey residue (affectionately known as "cheese" by the engineers). Even a little of this sticky goop can clog — and sometimes ruin — the tiny aluminum valves and fittings which feed fuel into the engines.

"In addition to the production of heat and other energy, the combustion of methanol results in carbon dioxide and water," explained Norm Hudecki, director of technical services for Valvoline, the official fuel supplier of CART. "As the engine cools, these bi-products can combine to create formic or carbonic acid, which results in the corrosiveness. The residue, then, is most likely the result of a reaction between those acidic solutions and aluminum oxide, a protective coating which forms naturally on the surface of all the aluminum engine parts."

A Solution

The solution to this problem is to flush the interior of the engines with a less corrosive substance. Gasoline was the ideal choice because it would allow the engine to be started, pulling the liquid through the entire system and burning off most residue.

"We recommend to all of our teams that any engine which is to be run and then stored for more than three days be pickled," said Paul Ray, vice president of Ilmor Engineering, the race engine-building arm of Mercedes-Benz.

To perform the pickling procedure, a small external gas tank with its own fuel pump is attached to the engine in place of its normal fuel pump and plumbing: gasoline cannot be put into the car's fuel cell because it would react with the rubber of the bladder.

Next, the gasoline is pumped through the engine, pushing out any left-over methanol into a waste bucket. An engineer watches the return hose until the liquid flowing into the waste bucket is no longer clear (methanol) but colored (gasoline). Finally, the engine is started and the gasoline flows through the injectors, cleaning them.

"When we run the engine it sounds very sick indeed," said Ray. "The reason is that gasoline has about twice the energy in it that the same amount of methanol does. So, when the engine is running on gasoline, the fuel mixture is twice as rich as it should be."

Ray also explained that in an ideal world the process would be reversed when the engine was again installed for running in a car, but because of time constraints, the engines are most often simply started up. They run poorly for the first few seconds, misfiring while the gasoline left in the system is burned off.

It is a far cry from your favorite sweet or dill pickle, but with the taste of six consecutive victories on the CART tour, Mercedes' engine pickling procedure does seem a recipe for success.

Mercedes-Benz competes in three major motorsports series around the world, winning races in 1997 in PPG CART World Series, Formula One and the FIA GT championship. The success and performance of Mercedes-Benz race cars exemplify the spirit of Mercedes-Benz passenger cars such as the new SLK roadster, the 1997 North American Car of the Year.

Source: Mercedes-Benz USA