Before installing aftermarket...
Before installing aftermarket performance parts on your car, it's best to first establish a baseline dyno run. Knowing how much power the engine made and what the power and torque curves looked like before the modifications lets you know where you've gained horsepower and torque, and where-if anywhere-it's been lost.
When the LS1 debuted in 1997, there were skeptics and critics galore. How could GM tinker with the sacred small-block Chevy, they asked, an engine that had long since proved itself to be the ultimate in reliability and performance, an engine that had won countless races and powered the Corvette to prominence since 1955? With bizarre-looking intake ports, no distributor, and an all-new block, how could GM's "new generation" small-block engine ever hope to top its legendary predecessor?
Almost 10 years later, what was once the little engine that could is now the little engine that can, will, and does kick the hell out of all other modern V-8s on the market today. Capable of 400 hp with basic performance mods, the LS engine is now the king of the streets. Coming from the factory with great horsepower ratings, the engine also responds well to bolt-on performance items.
After the baseline run, the...
After the baseline run, the crew at RevXtreme starts to remove the factory titanium Z06 exhaust system. While not a bad-performing exhaust, it does leave room for great horsepower gains.
On the C5 (both the regular and Z06 models), one of the biggest areas for power improvement is the exhaust system. As is typical with factory exhausts, the C5's pipes are restrictive and flow about as well as hurricane aid to New Orleans. But one thing to keep in mind when choosing an exhaust system for your Corvette is backpressure. Unlike older V-8 engines, the newer LS1, with its myriad computer controls and sensors, likes to have a certain amount of backpressure for maximum performance. Testing has shown that not enough backpressure can mean significant horsepower loss.
Enter Bassani, the performance exhaust company started by the infamous and colorful Darryl Bassani. Over the past several years, Bassani's X-pipe exhaust systems have stormed the market with their superb flow qualities and deep-throated sound. An ideal complement to the X-pipe system are Bassani's "4-2-1" headers. Their two-piece, slip-fit construction allows for easy installation in the tight confines of the Corvette's engine compartment, meaning you won't have to disassemble half of the engine or lift it off the motor mounts.
The Bassani chrome tips feature...
The Bassani chrome tips feature a larger 3 1/2-inch diameter, and their polished finish and etched Bassani logo give a discreet sign this Vette breathes better than stock.
Behind the headers Bassani offers a choice of two converter-back systems-a standard setup and a higher-performing (and louder) race-style system. At idle and 80-mph cruise, the standard system (which we selected for our test) is as quiet as the stock Z06 exhaust, keeping cabin noise to a minimum. But give the throttle a good goose, and the exhaust roars with an ominous growl.
For our installation, we went to Tampa's RevXtreme, a shop specializing in Corvettes and other GM performance vehicles. Once our subject Z06 was in the shop, Rev's crack team went to work strapping it down to the company's in-house chassis dyno. Before installing aftermarket performance parts on any car, it's best to first establish a baseline power run. Not only does it tell you where you've made gains, but also where you might have lost something. Overlook this step, and your dreams of increased horsepower and tire-shredding torque can quickly turn into nightmares of pig-rich idling and a humiliating lack of horsepower.
After the exhaust was installed,...
After the exhaust was installed, the Z06 was re-strapped to the dyno for its first test run.
Our baseline run yielded a max of 344 hp and 326 lb-ft of torque. After installing the exhaust system, the Z06 was run again without the aid of computer tuning. This run gave us a max of 350 hp and peak torque of 332 lb-ft. Our final run, after some computer tuning to compensate for a richer air/fuel ratio and a moderate knock-retard condition, produced a max of 368 hp and 349 lb-ft of torque. So, in the end, we gained 24 peak horsepower and 23 lb-ft of torque.
Jim Foos, owner of our test Z06, was extremely pleased with the sound characteristics of the new Bassani exhaust. Exhaust noise is minimal at steady rpm levels, but when the Z06's LS6 is winding up or spinning down, the sound is robust and healthy. Appearance-wise, the 3 1/2-inch chrome tips also add a nice touch of style to the rear of the C5. And heat issues? Bassani's exhaust didn't contribute any extra heat to the floorboards of Jim's C5, meaning the only hot foot he gets is when the accelerator is hammered to the floorboard.