The Corvette ZR1 looks and...
The Corvette ZR1 looks and performs on par with the world's finest exotics, but did Chevrolet limit its output by fitting it with a restrictive exhaust system? To find out, we're going to introduce the factory cans to the nearest dumpster and replace them with the Corsa RSC Track Exhaust System.
If you're looking for the ultimate in factory performance, nothing comes close to the Corvette ZR1. With its supercharged LS9 engine (churning out a factory-rated 638 hp), carbon-fiber-body good looks, and see-through-to-the-supercharger Plexiglas hood insert, the ZR1 is America's most popular dream car.
For those lucky few who own a ZR1, however, one of the common observations is that the factory exhaust doesn't supply the looks and sound characteristics the car deserves. In their minds, the ZR1 should have a set of pipes as awe inspiring as the rest of the vehicle.
Luckily, Corsa Performance Exhausts of Berea, Ohio, now offers a ZR1 version of its RSC Track Exhaust System (PN 14164), which features guaranteed horsepower gains, the company's patented Reflective Sound Cancellation (RSC) technology, and stainless-steel construction for long-lasting great looks. (The system also fits Z06 models.)
Our first step is to strap...
Our first step is to strap the ZR1 onto Backstreet Performance's mobile Dynojet dynamometer and ask company co-owners Rich and Erik Johnson to put it through three successive, no-holds-barred pulls. The best yields readings of 517.01 hp and 500.36 lb-ft of torque.
"Although the ZR1 is a superb vehicle and the flagship of domestic performance, its OEM mufflers lack sound from start-up and through the revs," Paul Santiago, Corsa's Sales Manager, explains. "Corsa provides a uniquely tailored exhaust note that could be best described as a blend of exotic supercar and muscle car all in one. At initial start-up, it already sounds like the supercar it is. [And] Corsa's promise of a no-drone internal cabin sound means that all 600-plus horsepower can be enjoyed at any level of speed without the fatigue experienced when the OEM muffler valve is manually left open during cruise."
According to Corsa, RSC technology reflects sound-pressure waves within the muffler case to produce the same 180-degree, out-of-phase, wave-cancellation effect found in electronic noise-suppression mufflers, without added complexity or flow restriction. As a result, Corsa is able to design a free-flowing, straight-through exhaust with awesome sound at full throttle and idle, while at the same time canceling low-frequency cabin resonance.
There's also a major difference in construction and materials between the ZR1's factory exhaust and Corsa's after-cat system. The ZR1 ships from GM with aluminized pipes and muffler casings, which are prone to deteriorate over time. Corsa, in contrast, "offers exceptional build quality and superb craftsmanship that make our exhaust systems almost jewelry-like. [They're] crafted of 321 military-grade stainless steel, the best in the industry for this vehicle," Santiago says.
Take a good look at the ZR1's...
Take a good look at the ZR1's stock exhaust tips and mufflers before we retire them for good. We'll show you a photo of the new Corsa tips and mufflers installed later in the story and let you decide which is the better-looking system.
We've featured Corsa exhaust systems in the past, and they've always provided a righteous rumble coupled with a drone-free cabin sound, along with stellar, stain-less steel looks any Corvette owner would be pleased to add to his or her car.
But what about horsepower? Did Chevrolet significantly limit the ZR1's output through its choice of pipes and mufflers, unwittingly giving Corsa and other aftermarket exhaust companies an easy way to uncork big power gains? There was only one way to find out-tear out a ZR1's factory exhaust, replace it with a Corsa RSC system, and dyno test the car to determine the power and torque differences.
We conducted our testing at Corsa's headquarters, which houses a professionally staffed R&D department where new exhaust systems are designed, tested, and installed before being released to the public. Backstreet Performance, "Ohio's Portable Dyno Specialist," provided the mobile Dynojet dynamometer required to objectively administer our tests. Company co-owner Erik Johnson made a trio of pulls with our ZR1 in stock trim, then repeated the routine immediately after the installation of the Corsa system.
We'll share the results of our test at the end of the story. Meanwhile, follow along as Corsa Lead R&D Technician Mark Bockwich shows how easy it is for you to install the Corsa RSC Track Exhaust System in one afternoon in your home garage or even in your driveway.
Now it's time to extract the...
Now it's time to extract the factory after-cat system. Corsa Lead R&D Technician Mark Bockwich uses a 15mm socket to loosen both of the factory
crossover-pipe clamps from the axle pipes (one on each side of the transmission).
Staying with the 15mm socket,...
Staying with the 15mm socket, Bockwich removes the two bolts and nuts connecting the factory crossover pipe to the converter pipes. (On the ZR1 or Z06, the lower two fasteners are bolts, and the upper two are nuts. On a standard C6, all four fasteners are nuts.)
The crossover-pipe assembly...
The crossover-pipe assembly is attached to the factory spring hangers by two nuts. He removes them with a 13mm socket, freeing the crossover-pipe assembly from its remaining mounting points underneath the Corvette.
The factory crossover pipe...
The factory crossover pipe assembly is a slip-on type, allowing Bockwich to easily slide it away from the converter pipes. This is necessary to allow the factory mufflers to be removed from the vehicle.
Bockwich cuts the factory...
Bockwich cuts the factory over-axle pipe (passenger side only), giving it more exit clearance and making its removal quick, easy, and safe. This step is critical to the procedure because it minimizes the chance of damaging the fuel and vapor-return lines, as well as the myriad wiring that runs along the underbody. Corsa suggests using a chain-style cutter for slicing through the pipe, as shown.
Bockwich sprays the factory...
Bockwich sprays the factory mufflers' rubber isolators with soapy water (for lubricity), then removes the hangers.
He then removes the rear sway...
He then removes the rear sway bar from its rear mounting brackets using an 18mm socket on the lower nuts and upper bolts, along with a 15mm wrench to hold the lower bolt heads stationary to prevent bolt-spinning (not shown.) Next, he swings the bar out of the way, creating the clearance necessary for the factory mufflers/over-axle pipe assembly to slide out.
The ZR1's factory dual-mode...
The ZR1's factory dual-mode exhaust is vacuum-activated. Bockwich removes both vacuum lines (one on each side) from their butterfly-valve assemblies.
With its over-axle pipe trimmed,...
With its over-axle pipe trimmed, the passenger-side muffler assembly slides out freely.
Removing the driver-side muffler...
Removing the driver-side muffler assembly requires extra care. Bockwich applies slight pressure to the transmission line so the factory over-axle pipe can slip by unobstructed.
With the stock exhaust fully...
With the stock exhaust fully removed, the ZR1 is ready for the Corsa RSC Track Exhaust System.
Before we get started on the...
Before we get started on the upgrade, let's compare the new preassembled Corsa system (on the left) to the ZR1's factory exhaust. It's easy to see that the Corsa set-with its 321 military-grade stainless steel construction-has better looks and, presumably, longer durability. In fact, it comes with a limited lifetime warranty.
A close-up view of the factory...
A close-up view of the factory 3-inch axle pipe reveals that it necks down to 2.5 inches as it enters the muffler. The factory tips are also a 2.5-inch internal design.
The Corsa RSC Track Exhaust...
The Corsa RSC Track Exhaust System (shown unassembled) features a fully-3-inch, straight-path design for the over-axle pipes and muffler inlets/outlets. The tips measure an even larger 4 inches.
Before installing the Corsa...
Before installing the Corsa system, Bockwich reinstalls the factory crossover-pipe assembly, repeating its removal instructions in reverse order.
He then reinstalls the factory...
He then reinstalls the factory crossover-pipe spring hangers, again by repeating its removal procedure in reverse.
Starting on the passenger...
Starting on the passenger side, he loops the Corsa axle pipe over the axle...
...and slides the new pipe's...
...and slides the new pipe's inlet into the factory crossover-pipe outlet.
He tightens the pipe into...
He tightens the pipe into place using the tack-welded factory clamp on the crossover pipe. Note: Bockwich tightens the axle pipe into the clamp so that it is not quite snug. He'll leave it that way and lock in final positioning adjustments later.
He then routes the driver-side...
He then routes the driver-side Corsa axle pipe over the ZR1's rear axle and slips it into the factory crossover pipe (not shown).
Next, he tightens the Corsa...
Next, he tightens the Corsa axle pipe to the stock crossover pipe, via the factory-supplied clamp.
Remember the factory vacuum-activated...
Remember the factory vacuum-activated dual-mode exhaust feature? Bockwich installs the supplied vacuum caps to seal off the factory vacuum line. (Additional instructions that come with the Corsa system show how to easily disable the factory dual-mode exhaust's electronics by removing a fuse.)
After sliding the Corsa muffler...
After sliding the Corsa muffler hangers into the factory rubber isolators, Bockwich slips the passenger-side muffler inlet over the Corsa axle pipe and attaches it loosely to the pipe with a supplied clamp using a 15mm socket (not shown). He repeats the process for the driver side.
Bockwich adjusts the Corsa...
Bockwich adjusts the Corsa system for tip rotation and exit length, then "snugs up" the mufflers to the axle pipe. (Note: Corsa recommends that you pay close attention to clearances around the rearend, transmission lines, and frame above the axles.)
He reinstalls the sway bar,...
He reinstalls the sway bar, loosely at first using sockets...
...and then uses a torque...
...and then uses a torque wrench to tighten the fasteners to 50 ft-lb (top) and 70 ft-lb (bottom).
Finally, he makes adjustments...
Finally, he makes adjustments so that the muffler tips are in perfect symmetry to each other and the ZR1's rear fascia.
Here's how the tips look after...
Here's how the tips look after installation. Notice how both the left and right sets of tips are equal distance from the top of the rear-fascia cutout.
With the Corsa system installed,...
With the Corsa system installed, it's down off the lift and back up on the Dynojet for three more pedal-to-the-metal pulls.
Incredibly, the car registers...
Incredibly, the car registers max peak-to-peak increases of 19.11 hp and 12.49 lb-ft of torque, making this one upgrade that more than lives up to its billing.
| On the Dyno |
| Stock Exhaust |
| |
HP |
TQ |
| Run 1 |
517.01 |
500.36 |
| Run 2 |
515.45 |
496.20 |
| Run 3 |
514.44 |
497.16 |
| Corsa RSC Track Exhaust |
| |
HP |
TQ |
| Run 4 |
536.12 |
496.35 |
| Run 5 |
530.20 |
504.46 |
| Run 6 |
530.26 |
509.65 |
Max Improvements (peak to peak): 19.11 hp and 12.49 lb-ft. (All runs were performed on a Dynojet dynamometer and are SAE corrected.)