HASN'T Chevy pulled this one before?
Camaro fans will certainly remember the fabled 302 smallblock. The 302 Bowtie mill was developed specifically to compete in race classes with a 305 cubic inch ceiling. On the street, the mill made its way into the Z28. On paper, the 302 was rated at 290 horsepower. On the dyno, the ponies were in excess of 400.
While the spread may not be as huge as 1969, there has been some delightful fudging of the numbers for our blown Chevy Cobalt SS tuner project. Before we started adding performance parts to the supercharged 2.0-litre ECOTEC, we decided to ask Sheldon Root and his team at Motion Performance for some time on the chassis dyno. Our last project car, a supercharged Toyota Corolla, returned practically identical output numbers when compared to the factory specifications. What story would the Cobalt tell?
With the car securely fastened to the dyno test-bed, Root began the first of three passes. Chevy pegs the blown 2.0 litre at a peak horsepower output of 205 horsepower at 5,600 rpm, with 200 ft-lbs of torque at 4,400 rpm. While scanning the specs, I noticed that the maximum rpm rating was pegged at 6,450 rpm. To prevent engine damage, this would be the number where the rev limiter would engage.
Root opted to test for peak output with a pass in both third gear and fourth gear. "Third gear is a lot easier on the car," said Root. "Standard transmission cars generally make the same power in every gear." The first run, which used fourth gear, took 18 seconds. "That's a long time," said Root. The third-gear run found the engine peak in about nine seconds. For the third run, Root opted to use fourth gear again for comparison. He pre-empted the run with one question. "Is it on warranty?" Yes, Sheldon. Yes it is.
It appears that Chevy will have to do some costly brochure reprints. At the factory-stated horsepower peak of 5,600 rpm, all three passes came in at or very close to an engine flywheel output of 235 horsepower, 30 more than stated by GM. Horsepower at the wheels ranged between 187 to 194. In third gear, the 6,450 rpm peak returned a peak horsepower output of 262.1 for the engine and 213.8 at the wheels. Maximum speed peak for third gear was about 160 km/h. In fourth gear, the rpm limit returned 245.8 horses for the mill, and 197.7 at the wheels. The virtual road speed was now up to 210 km/h. Just so we're all clear on this -- we haven't done ANYTHING under the hood yet!
What we will be doing in short order is filling the engine bay and undercarriage with the best bits from GM Performance Parts. Jim Gauthier Chevrolet Cadillac will start us off by installing an extrude honed exhaust manifold, as well as a stainless steel full cat-back exhaust. The system uses a muffler and resonator, which should mean that our Cobalt won't make noises akin to damp flatulence under acceleration. As we make our rounds to Winnipeg's GM dealers, we'll be installing a Stage 2 Performance Upgrade Kit. It includes high-flow injectors, an ECU re-program, as well as a revised supercharger pulley. This also means premium fuel is no longer a suggestion; it's required. There will also be an ECOTEC Performance Camshaft Set with adjustable cam gears. GM states that these upgrades should be good for a horsepower output of 245. (Which we already have.)
Different wheels are also on the way from GM, as well as some assorted bling. We're just in the process of locating the right suspension-lowering kit. There is a limited-slip differential available as an option on the '06, and we're looking into a beefier clutch more befitting the expected output.
Work on the car is being done by Winnipeg's four Chevrolet dealers -- Jim Gauthier Chev-Olds, Vickar Community Chevrolet, Orion Chev-Olds and Murray Chevrolet-HUMMER. The car was donated by General Motors of Canada. Dyno testing courtesy Motion Performance. Shell Canada has also donated the V-Power gasoline.
Have we missed anything? Send us your suggestions.
car-poll@freepress.mb.ca
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