Hammer Time

ProCharger’s blown C8 Stingray hits like a 725-horse sledge

Photo: Hammer Time 1
May 11, 2023

Let’s cut to the chase. Or more accurately, a high-speed pursuit in ProCharger’s C8. Stomp the throttle, and it takes off like a crazed cop car hot on the heels of a miscreant’s muscle machine. Of course, highway patrols don’t have any supercharged, 725-plus-horsepower Corvettes in their fleets, but if they did, nobody would ever get away.

This exhilarating performance was our experience manning the wheel at the Thunderhill Raceway Park in Norcal, easily hitting triple digits in a matter of seconds on the straightaway, with the centrifugal blower emitting a hungry growl. Yet such prodigious acceleration is linear, not overly abrupt—more like being flung out of a slingshot than the disruptive shock of an afterburner lighting off. So the car still feels controllable, with no wild fishtailing, albeit far more thrilling than a naturally aspirated C8. For while the factory’s LT2 engine does have loads of testosterone, the ProCharger delivers way more mojo.

This abundance of torque on tap leads to some obvious questions. How did ProCharger manage to squeeze a power adder and intercooler into the confines of the C8’s mid-engine configuration? And what’s entailed in both the installation and PCM tuning on the encrypted LT2 V-8? Lastly, how does it compare with the setup of the recently released 2023 Z06?

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In addition to fielding a wide range of high-performance street and racecars over the years, ProCharger has about three decades of history supercharging Corvettes—specifically, every generation since the C4. So when we first learned about an upcoming blower system for the eighth-generation model a few years ago, we were eager to visit the factory in Lenexa, Kansas, for some firsthand impressions. Sadly, the COVID-19 pandemic prevented that trip from happening, but our driving experience in a ProCharged C8 at Thunderhill served as fine compensation.

Regarding installation, we’ll summarize only the major steps of the procedure, as the clearly written manual provided by ProCharger is more than 80 pages long. For a DIY customer, it’s estimated to take a couple of days, depending mechanical ability, and using a dozen or so hand tools found in a typical rollaway. 

Before bolting on ProCharger’s centrifugal system, several items need to be disconnected, if not entirely removed. These include the battery, the trunk liner, and the plastic tray underneath the chassis, along with two access panels. The latter step provides access to the powertrain control module (PCM), which has to be shipped to ProCharger for reprogramming of the fuel delivery and ignition timing. Happily, the company says the process typically takes less than a week.

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After disconnecting the MAF sensor and PCV hose, along with some assorted harness clips, clamps, and electrical plugs, the air box can be pulled out and set aside. Additional sensors and solenoids are also unhooked in order to remove the intake manifold.

Overall, the good news is that the engine doesn’t need to be removed to complete the installation. But the manual does point out that when installing the drive assembly, “Accessing the bolts on the front of the engine will require patience.” To stay motivated, just keep in mind that invigorating driving experience described at the outset. 

The next major step involves fitting in the driveshaft assembly and billet intake manifold, followed by securing the ProCharger head unit to the main bracket at the rear of the engine (to be concealed later by a carbon-fiber cover). This cover has a provocative bulge, but we spotted photos of one ProCharged Stingray with a cutaway to expose the gleaming supercharger beneath, which in our view looks really impressive. After this sort of performance investment, why not show off what you’ve got?

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The install isn’t complete at this point, as a heat exchanger with a fan, plus an expansion tank, have to be added on the driver’s side, adjacent to the rear wheel well. And an intercooler water pump, too. A graph on ProCharger’s website illustrates the advantages of an intercooler, as it increases air density. (More oxygen means a more efficient combustion process, of course, and more power.) Along with that, ProCharger’s engineers located both the supercharger and intercooler away from the block in order to avoid the detonation and power-robbing heat sometimes associated with an engine-top mounting.

Why not use the more efficient and easier-to-install air-to-air intercooler, as was done on the C7? Space constraints dictated employing an air-to-water unit. Even so, ProCharger has successfully employed this configuration in very-high-horsepower applications.

Getting back to the PCM reprogramming, ProCharger already had experience with GM trucks, which gave engineers an advantage in cracking the C8’s E99 unit. As for the fuel injectors, company CEO Ken Jones says they have enough capacity to compensate for the torrent of airflow from the supercharger, so those remain stock. Otherwise, the firm provides all the tubing, brackets, hoses, and hardware needed. And if necessary, full custom reprogramming is available to ensure maximum results and reliability.

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Two different C8 packages are available from ProCharger: HO (High Output) and Stage II. Fitted with a P-1SC-1 head unit pumping out 5 psi, the HO setup costs $17,498. For the Stage II, which uses an upgraded P-1X supercharger pumping out 7 psi, the price is $18,498. Power increases over stock range anywhere from 170 to 230-plus horses at the flywheel, depending on the package and tuning. 

Speaking of tuning, a Tuner Kit upgrade is offered with either system. On the HO it includes timing control, and for the Stage II it’s supplied with a sheet-metal intake manifold, port injector bungs, and fuel rails. These kits are intended for buyers who plan to custom-tune their car to work with additional upgrades such as internal engine components. They’re also recommended for anyone who’s planning to experiment with alternative fuels such as racing gas and E85, or to employ methanol injection.

The basic Stage II kit has proved the most popular one with C8 owners thus far, and it’s also the one we drove, delivering 682 horses at the rear wheels. Jones feels the advertised 725-crank-horsepower figure is actually a little conservative, based on dyno numbers provided by many customers. Whatever the number, it enables consistent 10.5-second quarter-mile passes at 132 mph, according to a ProCharger engineer (and backed up by time slips posted on the company’s website).

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Given those figures, it’s reasonable to ask how a ProCharged C8 might stack up against a C8 Z06. Starting with pricing, expect to pay at least a $30,000 premium for the latter car, even after factoring in installation charges for the blower. Despite that upcharge, the 670-hp output of the rev-happy, flat-plane LT6 is still significantly less than that of an LT2 fitted with a Stage II system.

While ProCharger doesn’t provide estimated torque figures for the kit, a dyno graph the company supplied (shown) showed a peak rear-wheel figure of 574 pound-feet, considerably higher than the LT6’s 460 lb-ft at the crank. That makes for quicker throttle response and better low-rpm acceleration, two especially desirable traits on a street-driven performance car.

Granted, the Z06 has a more aggressive body, wing, wheels, and tires. And of course there’s the Corvette enthusiast’s cachet of owning a special-edition model (though in some instances driving a stealthier-yet-quicker blown Corvette makes quite a lot of sense). Another advantage of the Z06 is that it gets a specific tune for the suspension, and the desirable magnetorheological dampers come standard (they’re a $1,895 option on the Stingray).

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As for brakes, the Z06’s rotors are 1.2 inches larger than the Brembos included in the C8’s Z51 package, and carbon ceramic composition is standard on the Z07 package. Additionally, the front calipers are six-piston units compared with the Stingray’s four-piston setup. Based on our hard-charging track experience with the standard C8, however, the smaller binders scrub speed just fine.

A few technical provisos apply when bolting a ProCharger onto a Stingray. The system should only be installed on an engine with a factory compression ratio, and never on a worn or problematic powertrain. Also, the car needs to have certain gauges installed in an easily visible spot, to check the finished installation and monitor the vehicle’s performance, especially for testing. These include readouts for the manifold boost pressure and fuel pressure, as well as a wide-band oxygen sensor. In addition, any supercharged Corvette should always run on 91-octane or better gasoline.

On the emissions side, ProCharger has already applied for California Air Resources Board certification, and as of this writing the company is awaiting a response from CARB to become 50-state legal. In the meantime, these units are sold for “off-road” use in states that follow the California standards. 

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Also in the works is a ProCharger for the convertible C8, and even the Z06 at some point. Given that car’s already-abundant power, the prospect of adding a ProCharger is a real mind-blower—in every sense of the expression. 

Also from Issue 162

  • Big-Block ’69 Custom
  • Market Report: Special Editions
  • Owner-Built ’57 Restomod
  • Restored ’66 L36 Coupe
  • History: CERV II Targets Le Mans
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