Dietary Horsepower

Seeking the Truth About Lightweight Flywheels

Die-hard racers and serious performance fanatics are always looking for ways to save weight in their street or track cars. They know that weight robs performance. It's not unusual to see carbon-fiber body panels, gutted interiors, and lightweight wheels on track and some street performance vehicles. Reese Cox, owner of MTI Racing, is a die-hard racer. He is a former crew chief for a major Corvette endurance racing team and a SpeedVision (World Challenge) GT competitor, and he currently spends his time tuning customer Corvettes. He contacted Team VETTE with a wild idea--modifying both a brand-new ZO6 and one of his tuner ZO6s with a lightweight flywheel plus a high-performance clutch and pressure plate. Reese was convinced that we would see a nice bump in performance from both cars after such a change. Intrigued, we set up some test parameters. First, we wanted the cars tested on a drum-style chassis dyno to determine their rear-wheel horsepower. Next we required that each of the cars be pre- and post-dyno-tested on the same day. Reese agreed to our terms and to provide the cars and labor if we could find parts for the project.

Team VETTE has high regard for Fidanza products, so we contacted their Marketing Manager, Bob Sheid, with our idea. Bob was very excited about Reese's proposal and agreed to provide us with two of their latest lightweight flywheels. He also convinced us to install SPEC pressure plates and clutches into our test cars. Bob was so excited about our project that he decided to attend the installation along with owner Lou Fidanza to provide on-the-spot technical advice! We called Reese back and told him the project was a go. After all of the parts were delivered, Bob Sheid, Lou Fidanza, and Team VETTE met at Reece's shop in Marietta, Georgia, to start the project. As promised, Reece found a customer who volunteered his brand-new Commemorative Edition ZO6 for our test. We are not kidding about brand new! Denny Stradtman's beautiful new car only had a little over 700 miles on the clock. Our second test car is Reece's personal black '01 Z06 "development" car. This car has had its intake, heads, cam, exhaust, brakes, suspension, and wheels modified. It's fast and sounds bad.

Reese arranged to take both cars to a dyno before their modifications. First up was the new ZO6, which produced 357.3 hp and 351.8 ft-lb of torque on its third run. Water temperature was 191oF and oil temp was at 210oF. Outside temperature was 53oF. The runs were made in fourth gear from 2,000 rpm to 6,400 rpm, and it took 14 seconds for the car to reach its maximum horsepower. Now that we'd established a baseline, it was time to install the new parts in Denny's ZO6. Reese's crew consisted of himself, David Munder, Chris Harwood, and Jesus Garcia. In a blink of the eye, the center console, wheels, rear suspension, transmission, and torque tube were removed from the new ZO6. Next, the stock pressure plate, clutch, and flywheel were removed and weighed. The three factory parts hit the scale at 51 pounds. The new Fidanza 12.5-pound aluminum flywheel (PN 198571, retails at $439.00), and the 14.5-pound Spec Stage 1 clutch/pressure plate unit (PN SC091, retails at $299.00) totaled 27 pounds--a savings of 24 pounds of rotating weight at the crankshaft! The team installed the new flywheel, clutch, and pressure plate in record time, and they all fit perfectly. Three hours and ten minutes after the first wrench was turned, the crew had finished reinstalling all of the parts, and the car was returned to the dyno!

Fortunately our weather was holding and the outside temperature was 54oF for our repeat test. On the way to the dyno, we noticed a slight increase in clutch pedal pressure over the stock unit, but it was not annoying. Our best of three runs netted 366.6 hp and 360.4 lbs of torque--a gain of 9.3 hp and 8.6 ft-lb of torque. Maximum horsepower was achieved in 11 vs. 14 seconds with the stock parts, and maximum torque was seen in 9 vs. 11 seconds with the stock parts! Back on the road, Denny's Z06 revved a little quicker and required a lighter push on the loud pedal. We could feel the difference. Satisfied with our results, we headed back to the shop to make preparations for the next day.

The MTI team started the next day off by taking Reese's black, modified Z06 to the dyno. The outside temperature was 56oF, and three runs were made in fourth gear from 2,000 to 6,500 rpm. The third run produced the best readings with 437.5 horsepower and 376.2 ft-lb of torque at the rear wheels with the factory flywheel/ clutch/pressure plate. Water temperature was 193oF and the oil was 209. The car was returned to the shop to install the new parts. The team installed another Fidanza PN 198571 flywheel, this time with a SPEC Stage 3 Clutch with Hybrid Pressure Plate (retails for $699.00). The job took four hours because the long tube headers on this car are a tight fit and are difficult to remove. Back at the dyno, the outside temperature was 58oF, and Reese made three runs in fourth gear from 2,000 to 6,500 rpm. The third run produced 449.2 hp and 400.3 ft-lb of torque. Water temperature was 194oF and the oil was 210 degrees. This was a net gain of 12 hp and 21.10 ft-lb of torque. Maximum horsepower was achieved in 8 vs. 9 seconds with the stock parts, and maximum torque was achieved in 5 vs. 6.4 seconds with the stock parts.

At the conclusion of the tests, Reese shared his observations with us about installing the Fidanza and SPEC components into our test cars. "The important thing to look at in this test procedure is the time to speed relationship, not necessarily the increase in horsepower. Keep in mind the test device we used was an inertia dyno. A flywheel does not make any horsepower, but it shows up as a horsepower gain because you have reduced the inertia on an inertia dyno. So you need to look at the reduction in time to speed that was created by the reduction of inertia. We went from 14 to 11 seconds to 145 mph on the stock Z06. What that tells you is how the car is going to feel on the street. It is going to accelerate quicker to the redline."

And after all isn't that what we expect to gain from a good diet--more speed from less weight!

7

The Fidanza flywheels we used fit all '97-04 LS1 and LS6-powered Corvettes. The units are made from 6061T6 aluminum with a 1050 steel insert.

This high-clamp SPEC pressure plate gives a bit firmer pedal than stock, but it's not too stiff. The steel-backed, woven organic SPEC clutch disc offers all the performance and holding power that most enthusiasts will ever need.

Denny Stradtman loaned us this beautiful nearly new '04 Commemorative Edition Z06 for our stock test car. Note the low mileage on Denny's Z06.

Lou Fidanza (left), Bob Sheid, and Reese Cox discuss the dyno results of the '04 Z06 before the new flywheel, clutch, and pressure plate were installed.

The MTI team from left to right. Jesus Garcia, Chris Harwood, David Munder, and Reese Cox completed the flywheel and clutch swap on the stock Z06 in a little over three hours.

The differential, transmission, rear suspension, and torque tube have to be removed to make way for installing the new Fidanza flywheel, SPEC pressure plate, and clutch. Fortunately, it can be extracted as an intact assembly.

The new flywheel, pressure plate, and clutch were installed into the Z06. The drivetrain can now be reinstalled.

The '04 Z06 was strapped on the dyno again and readied for the second round of tests.

The MTI "development" '01 Z06 was being readied to have its new lightweight flywheel and clutch assembly installed.

Big wheels a turning, the Z06 spun up to 449.2 hp at 6,500 rpm with the Fidanza flywheel.

The dyno shop provided us with very concise graphs showing how the nearly new '04 Z06 performed both times on the dyno. Note the improvements to maximum horsepower and torque.

The before and after dyno results for MTI's "development" Z06 are shown here.

REESE COX

Reese Cox loves racing and going fast. He is a fierce competitor, has served as a crew chief and race driver, and now owns MTI Racing, a Corvette tuner shop in Marietta, Georgia. His daily driver is a very fast and equally loud, black on black Z06 that serves as the development car for MTI. A decade ago, Reese was Crew Chief for the Morrison Mobil 1 ZR-1 Corvette team, and he has worked with a who's who in Corvette racing that includes John Heinricy, Jim Minneker, Andy Pilgrim, Stu Hayner, Boris Said, and Jeff Nowicki. Later he started driving Camaros and Corvettes. He has won several championships driving cars he prepared. He was the first competitor to build and enter a C5 "box car" in the SpeedVision World Challenge GT series. The car was delivered as a rolling chassis, and the body panels were shipped separately in large boxes. Like a jigsaw puzzle with no instructions, Reese had to figure out what parts to order and how to assemble his new race car from scratch. While he never won one of these highly competitive races, he always ran near the front. TV commentators loved to focus on Reese because he was one of the most exciting drivers to watch during a race.

Today, a slightly mellower Reese has built a strong following in the Corvette community. He serves as a driving instructor in the Atlanta area and services a lot of customer cars that are driven in the street, as well as some that compete in track events. Chris Ingle is a Car Guys instructor who also competes in SCCA's T-1 category with a '01 Z06. Reese maintains the car for Chris, who is very high on Reese's mechanical skills. Team VETTE was very pleased to work with Reese and his team during the Fidanza project. It was obvious that they are very familiar with the C5. Just ask Denny Stradtman; he gave Reese his brand-new Z06 to use as our stock test car. If you are ever in the Atlanta area, stop by and introduce yourself as a fellow Corvette fan; Reese always loves to talk Corvettes.

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