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The New BMW 4.5L Daytona Prototype Engine
BMW went to Indianapolis for last weekend's Brickyard Grand Prix thinking small. Engine-wise, that is. They came with an all-new 4.5-liter Dinan-built M3-based powerplant. Half of the six BMW-powered DPs raced with new engines, compared with the 5.0-liter engines that were previously the only BMW engine option in the Rolex Series. Engine builder Steve Dinan was not concerned about going with a smaller engine.

"GRAND-AM does a good job of balancing things out. We weren't really worried about power. The reason it's 4.5 liters is that the block is shorter, and there's not enough room to stroke it to five liters – the parts wouldn't physically fit inside the engine. We might have made it 4.7, but GRAND-AM gives you a sixth speed if you're 4.5, and we decided the 200 extra CCs might not be as much as the extra gear."

The engine has been in development for more than a year. It had only one on-track test, by Pruett and Rojas for Chip Ganassi Racing with Felix Sabates at Watkins Glen International the day following the Sahlen's Six Hours of The Glen. "BMW and Steve Dinan have been working hard to get the new engine on track for the past year," Pruett said.

"BMW is committed to excellence and won't bring anything to the track without it being fully tested and prepared, and put in hours and hours of durability testing and development. The new engine ran exceptionally well at Indy. Finally, we feel we're competitive with the other engine manufacturers." There was one major concern about the new engine, though.

"It's pretty thirsty," Pruett said. "The smaller motor turns more RPM and gets worse gas mileage, and that was a disadvantage," Dinan explained. "It didn't turn out to be a problem at Indianapolis, but it might be at future races." Dinan said the new DP engine is similar to the ones currently being raced by the BMW M3 teams in the Continental Tire Sports Car Challenge – "although more aggressively tuned."

The 5-liter engine, the S62 currently in the No. 8 Starworks DP and both of the Team Sahlen's cars, is from the BMW M5. The change did not take place overnight. "There's been a lot of talk, a lot of discussion over the last year and a half to two years about making this transition from the current M5 derivative to the M3 derivative," Pruett said.

"The current engine we've been running is at the end of its life. It's seen everything it can see. It's done a great job for us. We feel making this next step is just the start of a new long future that we'll have together with it. "We did a little bit of a test at Watkins Glen," Pruett added.

"From my point of view driving it, the biggest initial challenge was shifting at the higher RPM. We've been used to shifting at 6,800 to 7,000 year after year, and that's significantly different. Another change is shifting into sixth gear as well. A number of those things don't seem big, but when you're used to doing it year after year after year end up being pretty significant." With all that said, what was the real reason for the switch? "The real reason we did it was the old engine's out of production at BMW, and BMW wanted to race a current engine that they're selling," Dinan said.

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