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Power grid - Engineer - GM Racing transforms Aurora V8 engine

Automotive Design & Production, Jan, 2002

The Aurora used in the Indy Racing League has (1) won every IRL championship, and (21 claimed victory in all but two rates. Right now GM Rating Is busily transformation this engine. And, oh yeah, it's now a chevy.

The situation facing GM Racing was unusual. Its Aurora V8 had won all but two Indy Racing League (IRL) events since the series began in 1997, but its identification with Oldsmobile, the nearly dead division, posed a growing problem the closer the division came to its termination date. This dilemma left the group with two options: depart the series at the end of 2002 with an unassailable lead, or regroup in 2003 under another banner.

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It did neither. Instead, GM Racing put the Olds brand on the racing shelf a year early, and replaced it with the Chevy bow tie. Then it produced a new engine around the Aurora's familiar Premium Racing V architecture, but sized and stressed from the start for life as a 3.5-liter motor with a "flat" (180[degrees]) crankshaft. This despite the fact that new engine rules--and therefore new engine designs--will arrive in 2003.

The IRL debuted in 1997 with a mandate for four-valve per cylinder, four-cam 4.0-liter V8s based around a production architecture. In time, the 10,500 rpm rev limit was reduced to 10,000 rpm, then raised to 10,700 rpm when the IRL lowered displacement to 3.5-liters. Later still, the IRL gave the competitors the option of running a 180[degrees] crankshaft in place of the production-oriented 90[degrees] crank so its single-seater series would sound like proper racers and not open-wheel stock cars.

"When the IRL put its rule package together, the bore center distance, cam drive (belt or chain), and other items had to be derived from the manufacturer's production 4.0-liter V8, multi-valve engine," says Roger Allen, chief engineer, Chevy Indy V8. Also set in stone were the cylinder bore diameter, the block's minimum deck height, and the minimum distance from the crank centerline to the sump. Along with a standardized set of mounting points, these items remain unchanged through 2002.

Nearly New

"We didn't have to start over with a clean sheet design," says Allen, "which meant we could work on those things that remained from the original 4.0-liter formula." In other words, though many of the parameters are common with the original design, the new engine--and Allen stresses that this engine is new--could be designed as a 3.5-liter engine from the start, which allowed a reduction in the center of gravity, weight, and reciprocating mass. "Only two parts--the oil and water pump assemblies--are carried over," says Allen. "We didn't see an opportunity to get an improvement from changing these parts."

After years of running the same basic package, the original design team had disbanded and moved on to other projects. Allen had to reassemble his small design team, and hire draftsmen and analysis personnel. He's the only full-time GM employee involved in the design of the engine.

Computer Power

"One advantage we had was that we were able to incorporate the latest design and analysis tools for computational fluid dynamics (CFD), computer simulation of the entire engine, and finite element analysis (FEA). A lot has changed since 1996, and many of the things we used to do on a mainframe computer, we now do on a desktop system." Some of the modeling involved studying how the aluminum alloy used to produce the block and heads flowed into the mold and hardened. According to Allen, "This was critical to eliminating voids, and making certain the part forms and cools in the proper sequence. We can't build 1,000 prove-out parts like a production program can because we can't waste the time or the money."

What About Production?

Ask him to compare this to a typical production program, including whether or not the lessons learned are applicable to high-volume projects, and Allen smiles before answering. "Even though I'm sure we could use our short development process to speed up what we currently have in place for production designs, the risk we take is many magnitudes higher than we're willing to take on a production engine," he says. Gut feelings about what will or won't work have no place in the production realm, where a mistake can cost billions of dollars. In racing, however, the loss is-at most-a few million dollars, slight embarrassment, and may mean nothing more than reverting to "the Aurora motor with a Chevy badge if the new one doesn't work."

Allen is quick to point out that a production engine costs less than one cylinder head on his latest creations. Therefore, losing $5/piston means nothing when you consider that Allen's cost is spread over eight cylinders per engine and a total of 100 engines. "There's no production-based manager who is going to look at what we do and say, 'Yeah, I'll use that'," he says. "He's actually more than likely to say something like, 'You do what?' instead."

This doesn't mean racing and production can't learn from each other. Theories can be tested, development ideas shared, and concepts debated, but there are few, if any, one-to-one swaps between the two disciplines.

Automotive Industry

Power grid - Engineer - GM Racing transforms Aurora V8 engine

Automotive Design & Production, Jan, 2002

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