2006 Chevrolet Corvette Z06 - Optimized,

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The Fine Art Of Not Over-Modifying Your Corvette
From the January, 2011 issue of Vette
By Chris Endres
Photography by Jerry Heasley

People often say it's an addiction, modifying your car. "Mod Fever," they call it. And once you get a little taste of making that car just a bit better, more often than not, you're hooked.
The trap many fall into is going willy-nilly making the mods they can make, rather than the ones they should make. Instead of thoughtfully devising a plan of action, taking into consideration their ultimate goals, those who randomly bolt on parts because they're the latest rage or simply look cool often wind up with a car that performs the same as or-shudder-worse than it did before they screwed with it.

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Steve Kepler is not among those who have fallen into the wholesale-modification trap. Much has been written of the C6 Z06's track prowess, and according to Kepler, it's all true. "There really isn't much this car needs to run hard at the track all day," the Waukesha, Wisconsin, resident explains. Having taken delivery of a factory-fresh black C6Z in March 2006, Kepler was no doubt tempted to whip out the credit card and start throwing parts at it. Instead, the sales rep for Johnson Controls (the parent company of Optima Batteries) patiently got to know his car, putting it through its paces at nearby Road America, evaluating its strengths and making note of its weaknesses. Soon, a plan came into focus.

Grunt is one thing the LS7 has in spades, but even so Kepler couldn't ignore the relatively simple power gains to be found in easing its breathing. The addition of a K&N air filter was an obvious choice. The wealth of aftermarket options for exhaust components made the job of choosing those pieces far less straightforward. After some research, Kepler selected a pair of American Racing's stainless-steel headers and teamed them up with a Magnaflow exhaust system. "The headers were installed by my local Dealer, Andrew Chevrolet, in May 2009. They fit perfectly and, along with the Magnaflows, sound great. The installer noted that these were the best-fitting headers he had ever installed. I agree that the form, fit, and function are perfect," Kepler says.

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A look under that lightweight hood reveals a stock, but clean, LS7. The only changes in the engine room consist of a K&N air filter and American Racing Headers.
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While the intake and exhaust changes made a positive impact on Kepler's ownership experience, it soon came time for him to turn his attention to more pressing matters-namely the braking system. While the motoring press (and, indeed, most owners) claim the big, upgraded brakes of the Z06 are more than up to the task of slowing the car, those who exercise theirs on-track know better. "The OE brakes change shape when run at high speed and the heavy braking that accompanies it, such as at Road America," Kepler says. Hard-core Z06 track rats know that this deformation leads to tapered pads and all sorts of attendant braking woes. The only real solution is an upgrade.

"The StopTech brakes were installed in September 2007 so we could test them in the Silver State 0-100-0 competition. The StopTech group showed great support by flying the brakes to us in Las Vegas, and we installed them in the parking lot at Sam's Town in a few hours," Kepler says. The install was completed just in time to hustle the car to Ely for the event. "We won and had the shortest overall distance." Kepler's Z completed the 0-100-0 run in just 11 seconds, covering only 1,218 feet in the process and generating 1.42 g's of deceleration force. "Needless to say, the brakes' performance has far exceeded my expectations." Kepler was also Sixth in the Silver State's 2007 standing-mile competition, with a top speed of 163 mph. The following year, with his younger brother, Mike, co-driving, Kepler won the 145-mph class at the Silver State with an average speed of 144.9986 mph.

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With both the go and whoa addressed, Kepler next focused his attention to maximizing cornering traction. For this, he turned to Pfadt Race Engineering. Pfadt recommended a set of its adjustable coilover shocks, which feature 16 different damping settings that are easily adjustable. The shocks' threaded bodies allow the user to make ride-height adjustments independent of spring preload. To give the car a crisp feel with decreased body roll, a pair of Pfadt sway bars feature torsional stiffness nearly three times that of the stock C6Z bars. In order for the car's balance to be tuned, the Pfadt sway bars are rate-adjustable. Lastly, the sloppy rubber suspension bushings were replaced with Pfadt's polyurethane/aluminum units.

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The entire suspension package was installed by Andrew Chevrolet. "This addition was probably the best aftermarket product I added to the car," Kepler says. "The coilovers keep the Z stuck on the ground and give it more bite than I could have imagined. We've run the car at Sandhills Open Road Challenge and in the Optima Ultimate Street Car Invitational exhibition class, and in both cases, the suspension instilled more confidence in taking turns at higher speeds than previous competitions. A few turns of the adjustment knob on the coilovers, and you can go from track to street in a few short minutes." And since Kepler's Z sees nearly as much track use as street duty, he's well versed and efficient at making the change from street to track. A change of brake pads and bolting on a set of Goodyear slicks on CCW wheels completes the transformation.

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High-speed open-road events require an onboard fire extinguisher. This is a smart addition for any car that sees track-day use, too.
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With the fresh confidence of the Pfadt suspension in place, Kepler elected to drive the 2009 Silver State one class faster than previously. "I ran in the 150-mph class in 2009 because it's a little more challenging with the max speed at 165 mph. There is also more competition in that class," he explains. Though he finished a slightly disappointing Fourth Place, he will be running the 150 class again in 2010.

Also on the agenda for 2010 is the Sandhills Open Road Challenge in Arnold, Nebraska, which most consider more of a drivers' course. "Silver State is an almost completely straight high-speed course that limits speed to 165 mph for a stock Vette with a harness. Sand-hills' max speed is 135 mph, and most of the course is run at 110 mph or lower," Kepler explains. "At Sandhills you really need a navigator to let you know which turns are coming up, and there are plenty of blind ones. I really count on Mike there. Course record speeds are also indicators of technical difficulty. At Sand-hills, it's about 135 mph or so, versus 205 mph for Silver State. I personally prefer and enjoy the Sandhills course."

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Inside, Sparco seats and Crow harnesses keep driver and co-driver pinned firmly in place at all times
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Kepler says he doesn't get to drive his Z06 as much as he wishes, as it is often touring other parts of the country as part of Optima's various publicity campaigns. Still, he has managed to rack up 12,000 miles on the odometer, mostly at speeds that would probably be considered unreasonable by most law-enforcement types. In true competitor fashion, he's always thinking ahead, of ways to go even faster. To that end, his future plans may include installation of a Magnacharger. He admits the prospect of having more than 700 lb-ft of torque at his disposal should be an interesting exercise in self-control, both on the street and exiting his favorite increasing-radius corners at the track. Somehow, it seems a certainty that he will find a way of optimizing it.

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Spec Sheet: '06 Corvette Z06
Owner: Steve Kepler; Waukesha, WI
Block: Stock LS7 aluminum
Displacement: 427 ci
Heads: Stock LS7 aluminum
Valves: Stock 2.200 titanium/1.610 sodium-filled
Camshaft: Stock hydraulic roller (0.591/0.591-in lift, 211/230-deg duration, 121-deg LSA)
Rocker Arms: Stock 1.8-ratio
Pistons: Stock hypereutectic aluminum
Rods: Stock forged
Crankshaft: Stock forged
Intake Manifold: Stock LS7 composite
Fuel Injectors: Stock
Fuel Pump: Stock
Ignition: Stock coil-on-plug
Exhaust System: American Racing headers with Magnaflow after-cat
Transmission: Stock six-speed
Clutch: Centerforce
Front Suspension: Pfadt adjustable coilover shocks and Pfatty sway bar
Rear Suspension: Pfadt adjustable coilover shocks and Pfatty sway bar
Rearend: Stock
Front Brakes: StopTech
Rear Brakes: StopTech
Wheels: Stock (street); CCW with Goodyear Eagle slicks (track)