Corvette Z06 Performance Packages - Inside The HPE Toybox

Stage III Stinger Package
The components of the Stage III Stinger package are identical to the Stage II's with the exception of one critical detail: the camshaft. While the Stage II cam's specifications are public knowledge, the Stage III's specs are shrouded in secrecy. Think duration in the 240s, with lift cresting 0.630 on a fairly wide LSA. When combined with the rest of the Stinger-package components, gains of 90-100 rwhp are possible.

Need more? If your goal is to generate almost 650 rwhp, HPE offers its $650 LS7 Nitrous Package. It features an NOS wet-plate kit designed to be used with the LS7's 90mm throttle body. The kit is jetted at 100 hp and, with the proper tuning, can be configured to safely turn the LS7 into a truly frightening beast.

HPE allows customers to customize the package with a wide assortment of convenience and safety accessories. Our subject Z06, owned by Vince Agriesti, had the following options installed:

* NOS Remote Bottle opener
* NOS Bottle Heater
* NOS Purge Kit
* MSD Electronics Digital RPM Window Switch
* HPE Installation

NOS Remote Bottle opener
Conventional Corvette nitrous systems require the user to pull over, pop the hatch, and exit the car to open and close the nitrous bottle. This option allows one to perform these operations without ever leaving the driver's seat. The billet aluminum opener features a servo-powered motor and fits all standard-size nitrous bottles. Integral to the design is a quick-release mechanism that allows the valve to be removed for bottle filling. Plug-and-play connectors and a switch are included.

NOS Purge Kit
To ensure consistency and maximum power, any nitrous vapor in the lines should be removed before the system is engaged. Otherwise, the liquid N2O may not be available to the nitrous solenoid immediately after engagement. The NOS purge kit comes with an electric solenoid, a 4AN adapter fitting, a 1/8-inch hex nipple, and fittings for the inlet and outlet.

NOS Bottle Heater
NOS recommends running a bottle pressure of 950 psi. This ensures that the gaseous content of the nitrous is fully converted into a liquid. In general, a temperature of 85 degrees Fahrenheit will provide the proper pressure. Bottle pressures below this range don't provide enough nitrous, causing the car to run rich, while excessive pressures can cause a lean condition.

NOS offers a 12-volt bottle heater that wraps around any standard-size bottle using Velcro straps. Add a bottle-heater pressure switch, and the user can open the nitrous valve, turn on the heater, and allow the adjustable switch to regulate pressure.

MSD Digital RPM Window Switch
This switch is used to determine the rpm range in which the nitrous system operates. When used with HPE's Stinger Packages, the switch is programmed to activate the system at 3,500 rpm and deactivate it at 6,800-7,500 rpm, depending on cam choice. The switch is wired directly into the Z06's ECU, from which it takes its rpm readings. It works in conjunction with the standard NOS WOT window switch, which is mounted under the gas pedal.

Nitrous System Installation
HPE's installation retails for $500 and is highly recommended. In addition to the challenges of mounting the solenoids and bottle brackets, a good knowledge of automotive electrical systems is required to ensure that the system operates properly and safely. Installation of accessories, such as the remote bottle opener, bottle heater, rpm window switch, and purge kit, runs $100 per item. (Because the package and accessories were installed together on our test car, the total labor cost was only $800.)

Owner: Vince Agriesti
Car: '06 Z06
Color: Black
Current Mileage: 4,200
Modifications: HPE Stinger Package and Nitrous

Because the LS7 ECU can't hold two separate tunes, the tuning on this Z06 was optimized for use with the nitrous system. Instead of aiming for a 12.5:1-13:1 air/fuel ratio, HPE tuned for a slightly richer 12:1. In addition, timing was slightly reduced. As a result of these changes, this car's naturally aspirated output is between 5 and 10 hp less than it would have been with the more aggressive, non-nitrous tune.

*Naturally aspirated run. The stock clutch stuck to the floor on the first pass, resulting in inconsistent clutch action for the rest of our test session. As a result, no nitrous passes were attempted.

Conclusion
The Tuning Package netted an impressive increase of 31 rwhp, while the Stage III Stinger and Nitrous Package combo peaked at a mind-boggling 232 rwhp. Even discounting the use of nitrous, the Stage II and Stage III Stinger kits put out 516 and 543 hp, respectively, easily breaking the 600-crankshaft-hp mark.

Chuck Anders noted, "A typical Z06 puts down around 435 to 445 rear-wheel horsepower in stock configuration on our Dynojet chassis dyno. Of the three cars tested here, each was a bit unusual in its baseline dyno pulls. Vince Agriesti's Z06 put down 411 rear-wheel horsepower, while Sanjay Mehta's put out 465. These are the lowest and highest numbers we have encountered with stock Z06s."

As with anything in life, the best-laid plans are often scuttled by forces beyond one's control. The people at Lonestar Motorsports Park went out of their way to make sure the track was in top-notch condition for our testing. Throw in clear skies and temperatures in the 50s, and we should have seen some ultra-quick e.t.'s. So what happened?

First, the factory Goodyear Supercar EMT tires were quickly overpowered at higher-than-stock hp levels. And when the Goodyears weren't scrambling to find purchase, they managed to stick well enough to obliterate Sanjay Mehta's CV coupler housing and put the hurt on Vince Agriesti's stock clutch.

More telling than the 60-foot and quarter-mile times were the trap speeds. Speeds of 130 mph without nitrous tell the real tale of what power lies in these modified Z06s. Had the clutch on Vince Agriesti's car not been so reluctant to put the power down, nitrous-assisted trap speeds would easily have topped the 135 mph mark. Now that's what we call a dangerous toy.