 Charles Beyer's '04 GTP Comp...  Charles Beyer's '04 GTP Comp G comes out of the chute at Cordova Dragway during the '05 GP Gathering. From the look of it, one would never guess this car was knocking on the 11-second door. |
 Under the hood of the Comp...  Under the hood of the Comp G we see the sanitary installation and the stock location of major components. A hollow blower casing is used as an upper intake manifold. |
 A Precision T-61 turbo is...  A Precision T-61 turbo is located in the area normally taken up by the stock airbox. Installation doesn't interfere with any underhood componentry. |
 Where's the blower pulley...  Where's the blower pulley and snout? Actually, the only thing left from the original Eaton Model 90 supercharger is the case itself. Beyer retained it as an upper manifold and removed the rotors and snout. The open end was closed up with an aluminum plate, which is available from Cartuning and is required when adding a turbo to the supercharged 3800 V-6. |
We recently had a chance to drive an '04 Pontiac Grand Prix GTP Comp G that ranks as one of the quickest street cars any of us had ever driven-period. How quick is that, you ask? You're probably thinking, "Sure, they're quick, but have you guys been piloting Azteks for so long that it's warped your sense of what performance is?"
Rest assured, this thing rips-with a best of 12.125 at 116.78, through the mufflers, no less. A chassis dyno session revealed it made 401 hp at the wheels. Do we have your interest now? The secret is a slick turbo kit from Cartuning (www.cartuning.ca) that mates a well-matched turbocharger to the 3800 V-6 to pump out some explosive acceleration, without the bad kind of explosions to spoil your good time.
"Wait a minute, don't the Comp Gs come from the factory with a supercharger?" you ask. "What's wrong with those?" Well, nothing really. The Eaton M90s are great for street use and give a tremendous amount of low-end power. The problem in using them is that they generate a lot of heat, are difficult to intercool, and ultimately, cannot flow as much air as even a moderately sized turbo.
Also, don't forget that a supercharger is crank driven while the turbo is exhaust driven. The more boost you try to make with a supercharger, the more power it takes from the engine to turn the supercharger. An Eaton Model 90 will require something along the lines of 35 hp to make 10 psi. Obviously, you have a net gain there, but if you consider a turbo doesn't take any energy from the crankshaft, the turbo will make more power from this fact alone (not even discussing efficiencies). While it is possible to get an Eaton M90-equipped GTP into the 11s or even the 10s, it will be compromised as far as street performance goes.
Charles Beyer, of Digital Horsepower (www.digitalhorsepowerinc.com), is someone who really appreciates a sleeper. You may remember his centrifugally supercharged '97 Grand Prix SE from one of our HPP Pavement Pounder Shootouts a couple of years ago. While it was a low-profile performer, it was not quite what he wanted. "I would still have that car today if this turbo kit was available back then," Beyer says. "The CSC worked great, but it was pretty loud. With a turbo, it's only noisy when it's making boost. The CSC wasn't god-awful loud, but enough that any potential victims would realize something was definitely not normal. The turbo isn't too 'noisy' (i.e. bad noise), it just doesn't audibly make itself known until it's too late."
This time around, Beyer decided to work over an '04 GTP Comp G, getting the additional benefits of an upgraded suspension and brakes. What's amazing about the finished product is that not only is it insanely quick for a front-drive street car (or any street car, for that matter), but it also displays flawless street manners.
Best of all, it is 100 percent bone stock except for the turbo kit itself, which includes some larger injectors and a PCM reprogrammed by DHP. There is absolutely nothing exotic or even aftermarket in the long-block. It uses untouched production heads, a stock cam, and a factory-issue bottom end-even the exhaust manifolds are production units. It's as-built Detroit iron assembled by union labor at GM Powertrain. 'Nuff said there.