Supercharged C6 Corvettes - One Thing Leads To Another

How A&A's Andy Green Huffed And Puffed A Pair Of Wicked C6s

Steve Temple Oct 4, 2010 0 Comment(s)
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We've found that Corvette owners are the restless sort, dissatisfied not only with most production sports cars (hence the reason for getting into a Vette in the first place), but with stock power levels as well (hence all the upgrades we feature on these pages).

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So we were hardly surprised to find that Andy Green of A&A Corvette Performance went through some wheelin' and dealin', plus some serious motor massaging, to fully realize the potential of his '06 C6 "Grand Sport."

"I've always liked [the Grand Sport] color scheme," Green explains. "But the original version was down on power, and I knew I could fix that." Fix indeed, since by the time he was done breathing on the engine bay, he had 735 ponies pounding the pavement.

It wasn't just about power, though. "I thought an '06 C6 would serve as sort of a 10th anniversary tribute to the original '96 edition," he adds.

Understanding his motivations, though, requires a bit of background, both on Green himself and on the yellow '08 C6 that served as a precursor to this project. In keeping with our initial characterization of Corvette owners as ambitious types, it is Green's self-assigned mission in life to test and refine, and then test yet again, a whole slew of superchargers and other performance parts. So when he took delivery of the canary-colored car at the Corvette Museum at Christmastime in 2007, he had a lot more goodies waiting for him under the tree. After getting a tour of the Bowling Green factory, and downloading some performance software right at the museum (using an HP Tuner), he bombed across country, by way of Graceland and Vegas, back to his Oxnard, California, shop to see what was stuffed into those stockings hung with care.

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Green eventually unwrapped five blowers-count 'em, five-to see what sort of power he could pull out of the LS3. Along the way, he experimented with a couple of camshafts and two different diff ratios, before finally settling on a 2.73. He also modified the exhaust four times before arriving at the current setup (a 3-inch B&B Fusion), along with bolting on Brembo brakes and Pfadt coilovers.

Before playing around with all these parts, though, Green first swapped out the engine with a built LS3, which had been prepped with ported heads from West Coast and fitted with forged Diamond pistons. Factoring in the slight 3cc dish on the tops and the 74cc bowls on the heads, he was able to drop the stock compression ratio from 10.6:1 down to 9.8:1, enabling as much as 13 pounds of boost from a Vortech T-trim centrifugal supercharger. That little jewel was good for as much as 680 horses, as verified by A&A's in-house dyno.

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Still not satisfied, he later switched to an Si-trim head unit on the car. That's because Green is fanatical about forced induction, making sure he squeezes out every bit of boost from his blower setups. As part of that process, he's figured out how to optimize the efficiency of the airflow. More about that in a moment, but first, a note on how this obsession with continuous improvement got started.

About nine years ago, and 10 Corvettes earlier in his personal collection, Green invented a simple little part called a Frame Saver. He hated scraping the nose of his C5 on a steep driveway or speed bump, so he welded up some brackets with casters on them and ran a small ad in the back of VETTE magazine. (Enterprising entrepreneurs take note: you too can become an overnight success, just by advertising in this magazine!).

Well, maybe not overnight, but within a year Green had moved his chop saw out of his home garage into a small shop, then a bigger one, and expanded his product lineup to include a bypass tube for the muffler. The latter component is no longer available, as one fateful day changed the direction of his fledgling company forever.

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One of his Frame Saver customers came into the shop complaining about the slipping belt of his blower (not a Vortech unit, though), plus some overheating issues. Green stared intently at the installation for a moment, and then a light went on. By adding an extra idler pulley, and moving the tensioner over a bit, the problem could be solved-almost. He also saw how much the airflow to the radiator was blocked, so he laid it down at an angle and relocated a couple other obstructions.

The customer was so happy, word of mouth prompted even more guys to show up at Green's shop to sort out their super-charger woes. Today, Green has more work than he can handle, but he's not complaining. He installs more than 100 superchargers per year, and ships out three times that number in mail orders. And business has never slowed, even in a sluggish economy.

What's the Secret to His Success?
Basically, it's practical, hands-on engineering. He makes sure everything works right, even those little Frame Savers he still sells (more than 5,000 of them, at last count). While the range of products he offers has expanded, his main deal is now superchargers, which he has relentlessly refined and fine-tuned.

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Green's approach emphasizes improving airflow management (for both the charge air and the ambient cooling air), along with custom tuning and a few other mods. Cooler air in a supercharger is especially important, as it improves efficiency with less risk of detonation on pump gas, allowing higher boost levels. Green points out that the positioning of the intercooler is critical, since a large intercooler located behind the frame is not as efficient as a smaller intercooler exposed to full frontal airflow. So A&A not only uses a larger intercooler, but also forces more cooling air through its core by means of a ram-air system. It scoops cooling air from under the front fascia and guides it directly into the intercooler.

The internals are important as well. A&A's intercoolers feature directional vanes in the lower tank to direct charge air evenly across the core. A&A also mounts the intercooler farther forward to minimize airflow obstructions, so the fans can draw air through the radiator and A/C condenser. While systems are available for both the C5 and C6, on the latter model the area next to the intercooler is closed in with aluminum panels, ensuring that any air fed around the sides of the 'cooler gets redirected back into the radiator.

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Lastly, since a slipping belt can reduce supercharger efficiency (recall Green's first blower customer), A&A has developed a bracket system with more wrap for additional surface contact.

Getting back to his yellow C6 testbed, in addition to all the mechanical change-outs, Green also threw on some Z06 fenders and a grille. But he admits that the latter item wasn't so much for airflow as for improved looks.

So what came next for this restless Corvette owner? He wasn't happy entirely with the automatic transmission, feeling a need to exercise his itchy left foot on a clutch pedal and slap a shifter with his right hand. So he stripped all the performance parts from his yellow car and sold them off for a fair profit, along with the car itself. That enabled him to step up to the C6 with the Grand Sport paintjob, which was otherwise factory stock. We'll give you one guess what happened next.

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Green installed a set of 9.5:1, 22cc dished Diamond forged pistons, along with his own custom blower cam (228/236 degrees of duration and 116 degrees of lobe separation). In addition to a new Vortech centrifugal supercharger, he refined the install with some trick-looking constant-tension clamps, an eight-rib belt, and American Racing headers, and then backed up the powerplant with an ACT clutch. Pfadt coilovers and sway bars settled down the chassis, and Wilwood's big-brake kit brings it to a sudden stop. He also modified the mufflers by inserting straight-through pipes, and threw on a set of '09 "Spider" wheels and Nitto rubber (275/35R18s up front and 335/30R19s in the rear).

Now that he's done, everyone thinks Green has some kind of special-edition mystery Corvette. And he likes it that way, keeping people off balance and not revealing all his secrets. But don't expect him to leave well enough alone, since he has even more plans for revamping his Vettes.

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