Showdown At Road Atlanta: C5 vs C6 Z06

We Built Our Pewter Rocket C5 To Take On The All-Conquering Z06.

Walt Thurn Oct 10, 2006 0 Comment(s)

The motoring press has been excited about the new Z06, and with good reason. With 505 hp and 198-mph top speed, the latest King of the Vettes is certainly deserving of all the praise it's received. But we realize many of our readers are attached to their C5s and may not be ready to step up to the new car. So, we wondered what changes would have to be made to a C5 in order to match a stock Z06's performance.

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Prior to the test, MTI put the Rocket on the dyno to verify the output of its stroked LS2. The 404-cuber managed an impressive 477 hp and 464 lb-ft at the rear wheels-around 30 hp and 45 lb-ft more than a typical '06 Z06.

Next, MTI adjusted the C5's ride height in the front and rear. The front was raised, and the rear was lowered, giving the car better balance.

Finally, MTI's Roman Hackett verified the Rocket's front and rear alignment settings.

We asked Reese Cox, owner of Atlanta-area Corvette-tuning shop MTI Racing. Reese answered, "We could accomplish this goal with the right changes to a C5. I have C5 customers who have asked me the same question." He went on to suggest that we modify Team VETTE's "Pewter Rocket" fixed-roof coupe to test out his theory. He even volunteered to pilot both cars around the 2.54-mile Road Atlanta road course to quantify the difference. "I've run enough laps around this course to determine which car is quicker. Road Atlanta will allow us to compare their engines, brakes, and suspension systems."

Intrigued, we asked Reese what kind of parts he thought the C5 would require. Thus began a series of articles detailing the conversion of our '00 FRC into a genuine C6 Z06 competitor. Our first article covered the building and installation of a new 404ci LS2 engine, which has proved extremely reliable and still produces close to 27 mpg on the highway. Our next story detailed how we added 35mm front and 25mm rear Addco sway bars, which made our project car much more responsive in turns. We followed that up by having MTI install Vette Brakes & Products composite 850-pound front and 750-pound rear springs, then finished off the suspension package with a set of Z06-spec EMT Goodyear tires and Factory Reproduction Z06 wheels from Mid America.

The final crucial upgrade involved the installation of stouter brakes, which came courtesy of Wilwood Disc Brakes. To make sure the Rocket could stop as well as it went, we installed six-piston front and four-piston rear Superlite calipers on 13-inch slotted rotors.

Prior to our test session, Reese re-dyno'd the engine (it was still plenty healthy, making 477 hp and 464 lb-ft at the rear wheels), adjusted the ride height, and aligned the suspension. After completing these changes, he test-drove the car and deemed it ready for action. Next, he recruited MTI customers Jeff and Darlene Sanderson to bring out their new yellow '06 Z06 for the test. Reese decided to drive each car flat-out for six laps while we handled the timing duties.

Reese took out our project car first and began setting a fast pace. His best lap was 1:35.4, and he stayed in the 1:35 range for five of the six laps. Next, he took out the Z06 and managed a best lap of 1:36.5. After he returned to the pits, we asked him for his reactions.

"I was astonished at how much grip the C5's Goodyear tires had. No matter what I threw at the car, it kept sticking! The transitional capabilities of this C5 came close to matching my C5 development car [which] is running close to World Challenge times at Road Atlanta in street trim on Hoosier tires. I usually feel a big difference between street tires and Hoosiers. You usually get an instant improvement in directional response, but not this time. These Goodyear's really stuck. I was pretty shocked.

"The engine in this C5 had torque everywhere. Even lugging it at 3,000 rpm coming out of a corner during my warm-up lap, it had buckets of torque. It made about the same power at 3,000 rpm that it did at 6,000 rpm. This was the big difference between the C5 and the Z06. The Z06 engine below 4,000 had nothing until the exhaust opened. Up top, both engines felt the same, and both touched 151 mph on the back straight. I had to spin the Z06 to 6,500 to feel the same power I did when shifting at 6,000 in the C5."

Reese was similarly impressed with the Rocket's handling. "I noticed a huge difference in the transitional capabilities of the C5 over the Z06. Since both cars had the same wheels and tires, it had to be the suspension setup. When you turned the wheel on the project car, it responded instantly. On the Z06 I noticed a lag, and you had to wait until it took a set before it responded. I think that is due to shock valving, spring rates, and sway bars. Handling-wise, the C5 felt better in every category. If you graded each car on road holding, feel, transitional capabilities, and overall precision, the project car would win hands down."

Finally we asked Reese about the brakes. "When I first went out on the course in the C5, the new brakes felt mushy, but after burning off the solvents from the new pads, the Wilwoods were wonderful. On the Z06 [the brakes] started out mushy and stayed that way throughout the test. I was actually losing time because I was braking early. My conclusion is the project car outscored the Z06 in every category. Not by much, but enough to make it quicker around Road Atlanta." We thanked Reese and the Sandersons for participating in our project and left with a big smile on our faces.

A couple of things became clear after completing this test. First, a new Z06 would need only minor modifications to match or exceed our heavily modified project car's performance. That's a testament to the inherent goodness of the car. Second, if you want to breathe serious new life into your beloved C5, you need but follow the modifications outlined in our article series. We promise you'll be amazed at the results.

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The Rocket is shown here exiting Road Atlanta's demanding Turn 12 at 120 mph. Notice how flat the car is in this corner. Look closely, and you can even see daylight under the corner of the right front tire.

MTI owner Reese Cox waits for the OK from the pit marshal before starting his evaluation runs in the Rocket. Having previously campaigned a C5 in the SPEED GT series, Reese has made hundreds of laps around Road Atlanta's 2.54-mile course.

After six hard laps in the Rocket, Reese jumped into the Z06 and quickly got it up to speed.

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