A recent discussion thread on seriousoffshore.com, a leading high-performance powerboating site with compelling message boards, caught my attention. The thread revolved around supercharging an Ilmor Marine (a division of Ilmor Engineering) 725 V-10 engine. Had it been done, could it be done, should it be done?
From the start, I saw an economic problem. Ilmor started production of its 725-hp, Dodge Viper-based marine high-performance engine in June of 2009. That means every one of those engines is still under the Plymouth, Mich., manufacturer’s one-year warranty. Modifying the engine in any way would void that warranty—and the cost of that warranty is built into the price of the engine.
But what about adding a supercharger to an Ilmor 725 after the warranty expires? Still not a good idea, according to Paul Ray, the president of Ilmor engineering, because extensive internal changes would have to be made to the engine to make it feasible.
“Ilmor engines are designed specifically as normally (naturally) aspirated engines,” Ray wrote in an email to me yesterday afternoon. “That is to say we maximize the performance of the engine by optimizing all of the components within the engine to give the best performance possible without supercharging.”
Ray explained that Ilmor took this approach for several reasons. First, the company wanted to differentiate itself from other high-performance marine engine manufacturers. Second, as racing-engineering outfit, Ilmor wanted to create a product that was “lighter than anything else that existed at the same power level.” Third, the builder wanted to produce an engine that was more fuel-efficient than other engines with the same horsepower rating.
“Supercharging the MV-10 engine can be achieved but not without changing the specification of the engine,” Ray noted. “To improve the performance we use a high static-compression ratio (10.3:1), which is too high for all but the most trivial of boost levels. Boosting therefore, would need a rebuild of the engine to lower the compression ratio—at minimum.”