[Merc1]

Inside the Supercharged 620-hp LS9 V8


GM isn't just kidding around with the supercharged 620-horsepower V8 that's at the heart of the 2009 Chevrolet Corvette ZR1.

It'll produce more urge than the absurdly powerful twin-turbocharged Mercedes V12 or the race-bred V10 of the Porsche Carrera GT or nearly any other internal combustion engine ever produced for vehicular transport. Most important, the 2009 Chevrolet Corvette ZR1's V8 makes more horsepower than the Dodge Viper's new 8.4-liter V10.

And it will carry GM's 100,000-mile powertrain warranty when the ZR1 goes on sale next fall as a 2009 model.

That's Just Super!

The secret to this ridiculous power output figure is no secret at all. It is in large part the doing of the Roots-type supercharger, one of the oldest tricks in the engine builder's book. More than a century after it was devised, this fundamentally simple air compressor helps Chevy's pushrod small-block (itself devised more than half a century ago) develop at least 100 hp per liter.

For those challenged by arithmetic, this means the displacement of the ZR1's engine is 6.2 liters, the same size as the V8 of the standard 2008 Corvette. But, you say, "Why wouldn't they throw the supercharger on the 7.0-liter Z06 motor and make, like, a million horsepower?" But Ron Meegan, the assistant chief engineer for the new 2009 Chevrolet Corvette ZR1's supercharged V8, replies, "The LS7 is a pretty polished beast. There's not much more to be had there."

Also there's the little issue of block strength. As it is, the 6.2-liter block, which is the same physical size as that of the 7.0-liter, had to be substantially strengthened for supercharged duty. Overall, the LS9's block is 20 percent stronger than that of the standard LS3.

Why not turbocharging? "Well," says ZR1 chief engineer Tadge Juechter, "we built a turbo car and it burned. We didn't want to get into turbo lag or any drivability issues. We wanted it to be quicker than hell but still fun to drive."

More Lobes, More Power

Juechter tells us that supercharging has been more important to the project than you might realize. He says, "Honestly, had Eaton not come up with this new, more efficient, sixth-generation supercharger, we might not have done the car at all."

Meegan tells us that Eaton's Twin Vortices Series (TVS) supercharger uses four-lobe rotors in place of the conventional three-lobe units, making it quieter and more efficient. The parasitic loss to drive the supercharger is around 70 or 80 hp, but it would have been more like 120 hp with the old supercharger, Juechter says. For the LS9, the supercharger cranks out 10.5 psi of boost.

And for those of you who dream of swapping out the stock supercharger pulley to make like a billion horsepower, be aware that Meegan says, "We don't want people to do that. We have not made that easy."

Wild Ride

The air molecules lucky enough to get sucked into the ZR1's V8 take a pretty straight shot through the intact tract, through the air filter, throttle body and into the supercharger inlet, nestled between the V8's cylinder banks. After that, things get a little circuitous.

The intake air molecules then get squeezed through the counterrotating rotors that look like gigantic black licorice twists. It then gets pushed up through a triangular hole in the top of the supercharger housing in between two long, narrow intercoolers. A 90-degree turn either left or right leads our molecular heroes to an intercooler that Meegan claims can lower the air temperature by 140 degrees F. The intercoolers are connected to a heat exchanger in the car's nose and filled with standard-issue antifreeze.

Once through the intercoolers, the now-chilled air takes another 90-degree turn down into the left or right cylinder bank of the engine. Here it will enter a combustion chamber (the compression ratio is 9.1:1) through intake valves that have the same diameter as those in the heads of a standard LS3 V8. The LS9's intake valves are made with lightweight titanium, however, and are set in cylinder heads made from high-strength aluminum.

Sandwiched between the heads and the block are head gaskets twice as thick as standard LS3 gaskets in order to cope with the upward force that's trying to send the heads through the hood. Upgraded fuel injectors are connected to a dual-pressure fuel delivery system (low pressure for low throttle load situations; high pressure for high load). New forged-aluminum pistons (cooled by oil squirters) are connected by titanium rods to the steel crankshaft.

Spent air exits through exhaust manifolds identical to those on an LS7 motor and through 3-inch exhaust pipes capped off by vacuum-actuated flaps as seen on the Z06. The LS9's oiling system is similar to that of the Z06's LS7 as well. It uses the same dry sump as the LS7 but has an additional 2.75-quart auxiliary tank that helps keep oil where it needs to be in a car that Juechter says can post lateral acceleration figures "comfortably over 1g."

It might seem strange, but the LS9 uses a lower-lift cam than the one used in the LS7, resulting in an idle that Meegan says is 11 percent smoother. Isn't this the baddest, leanest, most extreme, track-scorching, widow-making Vette from hell? Well, apparently, no.

Power Delivery

The monster motor is backed by a six-speed manual transmission that is a strengthened version of the TR6060 transaxle used on the standard '08 Vette.

This is a true close-ratio unit, unlike those of other Vettes, and 6th gear is no longer a fuel-saving ratio but instead the gear in which top speed can be achieved. "This buyer says, 'I can buy the gas. Just give me the performance,'" says Juechter.

A twin-plate clutch replaces the standard single-plate of all other Corvettes to handle the extra power and keep clutch pedal effort roughly equal to that of the Z06.

Show and Tell

Chevrolet is sufficiently proud of this supercharged small-block to give it its own window in the hood of the 2009 Chevrolet Corvette ZR1. In fact, the ZR1's signature feature is this clear polycarbonate porthole that reveals the LS9's integrated supercharger/intercooler unit. That should leave no doubt about which element of the ZR1 is most important.

We would imagine that the company could find more uses for this admittedly expensive powerhouse. Maybe GM should put it into all the Cadillac CTSs, Cadillac XLRs, Chevrolet Camaros, Pontiac G8s and — what the hell — everything else the company builds. If you believe Mr. Robert Lutz, GM's product potentate, future CAFE standards will kill all but the lowest-volume, highest-priced performance cars in the world.

Neither Meegan nor Juechter gave us fuel-economy estimates on the ZR1 and we didn't bother to ask.

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M

[Deutsch]

The interesting thing about the ZR1 is that they set the suspension to be softer than the Z06, because complaints that the latter could easily end up as a handful when driven enthusiastically. One of the main goals for the ZR1 was to make it easier to drive than the Z06 and easy to drive fast. Hopefully they accomplished that because a lot is at stake here with such an incredible amount of power being put down all at the rear wheels.

[DocM]

Respect to Chevy, it took them a while to wake up!
Now if they'd only remembered to tidy up that awful interior.

I think it's safe to assume that the ZR1 is the least expensive 620 hp car out there.

And, nissan with the GT-R also offer a great bang for your buck.
Germans, it's time to rethink your asking price

[Merc1]

I didn't see this earlier, but the roof panel and pillar trim are carbon fiber:



M

[Tycoon]

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[Just_me]

bye bye Skylie GTR

N-ring 7.30 min...

[DeDe]

Looks pretty damn good, and (after the Z06) I have to say this will be a great performance car!

btw: Why is it a '2009-model'? I still don't get it...

[Merc1]

Well it doesn't go on sale until the fall of 2008, making it a 2009 model by U.S. standards.

M

[Centurion]

Monstrous, but does it have launch control or something to help get all that power down to the ground?

[Merc1]

Nope, just 12 inch wide rear tires!!!

M