NASCAR Sprint-Cup Series
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CUP: Under The Hood - Engine Package Provides Power To Perform
Each race track - from superspeedways to road courses - places its own set of demands on NASCAR Sprint Cup engines...
SPEED Staff  |  Posted August 28, 2010   Charlotte, NC
“Under The Hood Presented by Quaker State” is a series of behind-the-scenes articles about Hendrick Motorsports.
Editor’s note: “Under The Hood Presented by Quaker State” is a series of behind-the-scenes looks at what Hendrick Motorsports does to remain at the front of the hyper-competitive world of NASCAR Sprint Cup racing. This week, Jeff Andrews, Director of Engine Development at Hendrick Motorsports, talks about different Sprint Cup engine packages.

To the untrained eye, the 358-cubic-inch Chevrolet W07 Sprint Cup engine looks pretty much the same under the hood, whether teams are racing at a high-speed track like Michigan International Speedway, a short track like Martinsville Speedway or even one of the two road courses on the circuit.

But the reality is very different.

Each race track puts its own unique demands on engines, so even though the engine block remains the same everywhere teams race, there are lots of options for engine tuners to get the proper amount of power in the engine at the right place in power band.

So the engine a team runs at Martinsville is not at all the same as what it runs at Michigan.

“They are a lot different internally,” says Jeff Andrews, Director of Engine Development at Hendrick Motorsports. “It has to do with, basically, the RPM (revolutions per minute) range that the engine will run in and the amount of time it will spend in the range.”
Jeff Andrews, shown here earlier this year at Richmond International Raceway, is the Director of Engine Development at Hendrick Motorsports. (Photo: LAT Photographic)

And those factors vary from track to track.

“For example, at Martinsville, the low RPM in the corner, might be 4,500 RPMs, and the maximum RPMs at the end of the straightaway is somewhere in the neighborhood of 9,800 RPM,” says Andrews.

At Martinsville, which is only 0.526 miles long, the two straightaways are just 800 feet long each.

“So you have an an acceleration rate that’s very quick because the straightaways are so short,” says Andrews. “The engine has to have a lot more power moved to the lower RPM range to accelerate the car up off the corner quickly.”

That’s much different than the 2-mile Michigan International Speedway, where the frontstretch is 3,600 feet, more than four times as long as at Martinsville.

“At somewhere like Michigan, you’re running a more sustained RPM and a higher RPM range,” says Andrews. “And the acceleration rates are much lower, so you want to move your power band to operate in, say, the 7,400 to 9,400 RPM range. Much tighter — a 2,000 RPM range, where in Martinsville it’s more like a 5,000 RPM range.”

So how does the team move the power band around? Change components in the engine.

“Specifically, camshafts and intake manifolds are the two things you use to alter the valve events to build more lower speed power,” says Andrews.

“And with intake manifolds, you work with the runner lengths inside the manifold. Of course, the exterior of the manifold is fixed by NASCAR — that dimension can’t be changed — but inside, we can do certain things with the volume of the intake runner and the runner length, which picks up or increases the air speed at lower engine speeds. That improves the volumetric efficiency of the engine at lower speeds.”

All these parts and pieces, of course, have to be rigorously tested before they ever get to the track. Hendrick Motorsports, like other top teams in NASCAR, can ill-afford part failures, so the team does its utmost to ensure its parts are all battle-ready before the race even begins.

Hendrick has dedicated engine dynamometors that are used strictly for testing new components. “When something we see has the potential to make more horsepower, then we have to go through a phase of understanding the durability aspect of it,” says Andrews. “Will it make it? Will it survive?”

So the team tests components and then tests them again.

“Before a new engine package would get here to the race track in a car, it will have already run four 800-mile races at the shop,” says Andrews. “Four different engines, 800 miles each. Then we’ll disassemble them and look at them and make sure they work.”

And that’s just one more reason why Hendrick Motorsports has won more championships since 1995 than the rest of the NASCAR Sprint Cup field combined.

Read more... “Under The Hood Presented by Quaker State”
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