Even though bolting on a blower is one of the most cost-effective ways to achieve power gains on your Corvette, nobody ever said superchargers come cheap. Not only that, but other hidden costs can crop up during installation and tuning. And there's one more big expense that might need to be factored in: replacing the factory hood with a taller, aftermarket piece that clears the blower case. (And that doesn't include prep and paint, which can really add up if you need to match your Vette's custom hues.)
All of which leads us to Edelbrock's new E-Force Supercharger for '08 to '10, LS3-powered Corvettes. How so?
"One of our primary requirements was to have it fit under the hood-but with no sacrifice in performance," notes Robert Simons, the company's vice president of research and development. After all, why force a customer to spend at least a couple grand above and beyond the price of the puffer, just to get it to fit?
Of course, there's a lot more to the unit than the packaging. Edelbrock prides itself on attention to details and innovations in design that not only improve performance, but also simplify installation. After driving Vic Edelbrock Jr.'s supercharged C6, we spent a significant amount of time going through the layout of the E-Force system with Simons. We came away with a renewed respect for how much effort the company expends to ensure that its parts both fit and perform as claimed. In this case, the resulting engine output comes pretty close to a ZR1, but at a fraction of the price.
Cutting to the juicy part, the power levels that can be reached are impressive, hitting as high as 599 hp and 547 lb-ft of torque at the flywheel in the 7.5-psi Street kit (PN 1591), which comes with a high-flow fuel pump and a 3.50-inch blower pulley. That's a gain of 164 horses, or a 37.7 percent increase in output!
If you prefer not to swap out the factory fuel pump that's embedded in the tank, you can still achieve 554 horses and 515 lb-ft of torque with the 5.5-psi Street kit (PN 1590). You can always upgrade to the higher-output version later on if desired, but note that the E-Force is not currently compatible with Z06 or ZR1 models. It will fit on a '10 Grand Sport, though.
Since the LS3 has a higher compression ratio than the LS9 (10.7:1 versus 9.1:1) and no forged internals, the boost can't go as high as the 10-psi level seen on the ZR1. However, a Competition version of the E-Force is available as well, using a pulley as small as 2.75 inches in diameter. Power output will depend on the engine combo in question, with boost levels ranging from 7.5 to 18 pounds. This system is based on the 1590 Street supercharger but pared down to the bare essentials, leaving off extras typically customized by racers for a competitive advantage.
These power levels result from a combination of Eaton's new rotor design (also used on the ZR1) and Edelbrock's unique application and enhancement of the technology. As noted in a previous article, Eaton's axial-flow TVS (Twin Vortices Series) supercharger has dual four-lobe rotors with a 160-degree twist. The much higher helix angle, along with refinements to the port geometry, is designed to minimize pressure variations for a smoother discharge of air and higher efficiency over traditional Roots units.
Edelbrock optimizes the design even further in a variety of ways, from the blower-case configuration to the hose fittings on the intercooler. In contrast to other positive-displacement systems, the case was not only rotated so the inlet and drive pulley are at the front of engine, but also inverted so airflow goes upward. After exiting the case, the air goes through air/water intercoolers on the sides of the unit (rather than on top, like the ZR1). It then feeds into 12-inch runners underneath the case, which dump into the heads.
The advantages are numerous. The front-drive, front-inlet configuration makes for a shorter intake path without the use of a jackshaft. Also, on the ZR1 version, the coupler is encapsulated with a large casting that blocks airflow to the rotor on the passenger side. The E-Force system dispensed with this casting by using a Teflon seal on the coupler, which provides freer airflow to the passenger-side rotor.
The side-mounted intercoolers lower the profile of the blower case so the entire unit can fit under the stock hood. In addition, the long intake runners below the case offer several benefits.
One is more low-end torque for crisper throttle response. The temperature distribution of the cylinders is also better with longer runners. "Typically we see a 60-degree spread, but it's only 20 degrees on the E-Force system," Simons notes. That makes tuning more precise, since you typically have to tune to the hottest cylinder, he points out.
Another benefit of the runners is a lower boost level at low rpm, since they get air out of the plenum more efficiently. Under light-throttle conditions, an integrated bypass valve minimizes parasitic loss (by removing load on the supercharger) to maintain fuel efficiency.
"A longer runner is tuned to maximize the scavenging effects of the oscillating pressure wave, in the lower-rpm range," Simons adds. "The name of the game is airflow-tuned intake runners reduce restrictions."
To keep up with the increased airflow, Edelbrock supplies the same-size injectors used on the ZR1 (52-lb/hr), but mounted at the end of the runners so they don't interfere with airflow. The ECM's fuel map is modified as well, with a handheld programmer for downloading proprietary software. Edelbrock engineers handled all the calibrations in-house, derived from testing done on both engine and Eddy-current chassis dynos.
"That took a lot of time," Simons admits. "And the Eddy-current is the most important, as it allows varying the loading for more-precise programming. We use it to improve driveability."
Speaking of driveability, for all the sophistication of the E-Force design, Edelbrock didn't neglect to focus on a more fundamental aspect: the belt system. "Superchargers are notorious for throwing belts," Simons says. "So we designed a six-rib belt system with maximum wrap and a new tensioner with twice the throw and torque. So there are no belt issues."
How about emissions issues? Edelbrock says CARB testing has already been completed, and an EO number is expected before fall. In the meantime, the company is already shipping out E-Force systems. Extended warranties are available, as much as five years and 100,000 miles.
Installation time is estimated at 10 hours, facilitated by the molded connections and fittings on the pre-assembled hoses. In addition, no plumbing of oil lines is required, since the blower case has a self-contained oiling system with a 100,000-mile service interval.
Getting back to the driving experience, there's no question that Vic's Vette has way more beans under the hood. Even so, he prefers a subdued exhaust note so it's more of a stealth bomber. The traction control kicked in pretty quickly, but we were reluctant to switch it off and hammer real hard on his personal car, even it was fitted with the Z51 suspension and Edelbrock IAS shocks. So maybe we smoked the tires a little, but let's keep that just between you and us, OK?