Tom Wilson
August 1, 2009
Photos By: Courtesy Of Edelbrock
Seen during installation without its decorative coil-cover side panels, the E-Force supercharger still stands out as a handsome addition to the top of an S197 Mustang engine compartment.

Although we've been there many times, we always get a bit of automotive acrophobia when taking in Edelbrock's main facilities in Torrance, California. Besides the unparalleled history of the place--Vic Edelbrock Sr. started the company in 1938--the scale of the business sets us back. Most automotive performance aftermarket companies are some version of cottage industry, but Edelbrock is high-performance on an industrial scale.

Such a feeling is difficult to ignore when walking among rows of busy CNC machines, going from room to room holding manufacturing, shipping, warehousing, marketing, and corporate offices, or ogling the latest in rapid prototyping capabilities. And then you realize this is just one of three Edelbrock campuses in Torrance; there are two additional foundries, one for sand molds and another for permanent molds, in San Jacinto, California.

So it's with an understanding that Edelbrock doesn't just off-handedly toss parts into the aftermarket that we went to inspect Edelbrock's E-Force supercharger at close range. We had seen the new blower at the SEMA show, but this was an in-depth visit to study, install, and dyno the new blower for '05-'09 Mustang GTs--and '10 GTs after Edelbrock gets a chance to verify the fit.

Here's how the E-Force comes out of its shipping box, except that the fuel injectors and rail have been added for a little highlight. There's no need to fiddle with any difficult or sensitive blower assembly work because it's done at the Edelbrock factory.

What we found is a supercharger aimed squarely at the center of the street market with a performance reserve for track-oriented cars as well. Edelbrock's design philosophy with this supercharger is to provide a fully engineered product the average enthusiast can bolt onto his real-world street S197 Mustang and have some fun. There is a higher-output competition version of the E-Force, but the emphasis is not on trailered, rollcaged race cars.

A quick review of Edelbrock's in-house testing shows the E-Force makes over 400 rwhp on the company's SuperFlow chassis dyno in the 6 to 8 psi range, which jibes with the 466 flywheel horsepower shown in the ads. Combined with the 439 lb-ft of torque at the rear tires, that's a definite bump in the backside. We also saw a touch over 600 flywheel horsepower (up to 650 now) on Edelbrock's built, free-breathing Three-Valve dyno mule, so there's power to be had here.

Recognizing it would be impossible to better a dedicated specialist when it comes to the heart of supercharger design, Edelbrock teamed with Eaton Corporation for the fundamental guts of its new supercharger, the rotor set; Edelbrock builds the remainder of the supercharger.

Edelbrock's E-Force layout is distinctly two-story. Downstairs is the supercharger itself, along with the air inlet, drive snout, and bypass valve. Upstairs is populated by the charge-cooler core and the intake runners. By arcing from the far side of the manifold, over the top of the charge cooler, and then down into the ports, the intake runners are long for good off-boost torque.

Eaton is a large OEM-level supplier, and we've all seen its superchargers before on Thunderbird Super Coupes and the '03-'04 Mustang Cobras, along with numerous Aston Martin, Mercedes and others. For the Edelbrock E-Force supercharger, the latest TVS rotor set was chosen. This is the same rotor set used in the ZR-1 Corvette. It's a four-lobe, 160-degree twist design displacing 2.3 liters of air per revolution. Eaton uses Twin Vortices Series--TVS--to denote this highly twisted rotor design.

There has been much discussion comparing the merits of the twisted-Roots design of the TVS blower versus the male-female arrangement of twin-screw compressors, and frankly, we don't intend to settle that argument here. Both are advanced designs, and at anything approaching normal boost pressures, the differences between these designs is likely academic. By the time one supercharger shows superiority to the other, it's likely time to bolt on turbochargers anyway, so we'll leave it at that.

One place where the TVS has an edge is price. Edelbrock is able to sell its Mustang supercharger for $5,795.99. This is notably less than the newest twin-screws on the market, but how much of the price delta is attributable to the price of TVS rotors or simply Edlebrock's economy of scale is impossible to determine.

Turning the input casting around and looking through the throttle-body opening shows just how unimpeded the airflow is once past the throttle body. A kiss from the CNC machine--visible on the right of the throttle body opening--helps port-match this casting to the Edelbrock throttle body.

As the largest rotor manufacturer in the world, Eaton also brings an OEM level of machining, gear finish, and other niceties to the table. This pays off in extremely quiet blower operation--the injectors are noisier at idle--and capable customer support.

The project engineer on the Edelbrock blower is Rob Simons. He is a Saleen ex-pat, where he engineered on hot Mustangs and the S7 exotic among others. Ironically, this puts him in a competitive position with his old compatriots who are now working across town at Techco. You may recall those other guys just released their own supercharger, which we reviewed last month. Funny how small the world is sometimes.

Rob did all the design work on the Unigraphix 6 software; in turn, the finished programs were fed to Edelbrock's SLS FDM and rapid prototyping 3D printers (which "prints" parts using melted ABS plastic "ink") to quickly check fit and airflow. Such rapid prototyping has seemingly overnight become the standard method for better-funded aftermarket companies. It's an amazingly powerful set of tools and really leverages the promise of digital design.

A simple bypass actuator is used on the outside of the supercharger case. It uses the industry-standard vacuum motor and non-adjustable linkage.

The design capability yields a complete, relatively easy-to-install kit. Our advice if installing the E-Force at home is to budget all weekend for it, strip down the engine and bumper cap on Friday night, and then hit the installation proper starting Saturday morning. It can be done in two days, of course, but we advise you finish up earlier on Sunday rather than eight hours before you drive your Mustang to work on Monday morning. Leave those antics to magazine production.

At the other end of the air gun are some pro shops claiming they can slam on an E-Force in a mere 3.5 hours. You could sell tickets to a show like that. We expect something closer to a day and a half for most pro shops as there is little way to hurry the wiring, neatly route the hoses, and that sort of thing. Anyone quoting a few hours installation is putting a whole squad of people on the project.

Inside the case the bypass blade is visible at upper right. It allows air to communicate between the supercharger and charge-cooler sections, nearly eliminating the power load to rotate the supercharger under cruise conditions. The open nature of the rotor inlet area is also visible here.

You'll note our installation is on a Bullitt, not a GT. The only mechanical differences are the addition of the Bullitt's strut tower brace--it clears the E-Force as if made for it (ironically, Edelbrock's own strut tower brace doesn't because it picks up the cowl in addition to the strut towers)--and the cold-air induction. Electronically, the Bullitt doesn't get along with the pre-programmed files in the Diablo, but Edelbrock and Diablo sorted that out so it isn't an issue with customer kits.

We think the E-Force is a contender for S197 blower glory. The pricing is attractive for a positive-displacement blower, the hardware is OEM quality, and installation on par with the market. Reserve capacity appears good for those wanting to step up the boost, and Edelbrock products are available everywhere. There's even an optional warranty.

We also had the pleasure of driving the Bullitt test car for a quick street evaluation. It's a blast, with a good torque hit and a strong pull all the way to the fuel shut-off. This type of power is perfect for the current crop of heavier Mustangs, the ample low-rpm torque starting the fun right away and lasting right through to redline.

Off-boost the Edelbrock installation ran like a stocker, with good low-end power and response thanks to its long intake runners. The Edelbrock supercharger is also hushed, easily the quietest of the current crop of positive-displacement superchargers. Off boost there is essentially no blower whine, and a non-enthusiast (that's your mom, Bub) would never know the car is blown.

The two water fittings for the charge cooler are AN with slip-on connections. If threaded AN braided hose is desired, it's as easy as substituting the appropriate AN fittings.

On boost, the E-Force does emit a rather polite blower whine but it's subdued. You'll hear it and get a kick out of it for the first week after bolting on the blower, but after that, it's just another sound you sorta forget about because its mainly in the background. Put another way, we can hear the blower if the windows are rolled up and we hit the gas, but if the windows are down, the stock exhaust note drowns out the blower whistle.

The 3.73 gears in the Bullitt are a good match. They aren't too low in First for standard driving, and really get the car out of the hole when trying hard. Switch off the traction control, turn her in aggressively, hit the gas, and it's easy to play drift king.

On The Dyno
Edelbrock has three engine dynos and one chassis dyno in house, so they have plenty of data on the E-Force supercharger. In round terms, they rate it at 466 hp and 439 lb-ft of torque at the flywheel. On its chassis dyno, it typically makes around 410 rwhp. As expected, the E-Force puts out the smooth, textbook-flat torque and rising horsepower curves associated with a positive-displacement blower.

The Bullitt in the installation photos posted 404 rwhp at 6,281 rpm and 386 lb-ft of torque to the rear tires at 4,362 rpm on Edelbrock's SuperFlow chassis dyno, detailed in the dyno figures shown here. Of course the power peaks don't quite land on the exact rpm figures we've listed, but those are the peak numbers. In our previous Bullitt experience, a stock Bullitt lays down 264.90 hp and 282.22 lb-ft of torque to the tire on a Dynojet, so call the E-force a 140hp upgrade.

RPMPowerTorque
2,{{{900}}}197.4358.7
3,000214.8372.0
3,{{{200}}}232.9379.0
3,400250.7384.5
3,{{{600}}}264.6383.7
3,800279.3384.1
4,000295.1385.8
4,200309.4385.5
4,400324.2386.0
4,600338.5385.8
4,800347.8380.4
5,000360.6375.7
5,200368.5370.0
5,400375.9364.7
5,600383.6360.1
5,800392.9354.8
6,000400.1348.4
6,200403.6342.0
Once the heat exchanger and pump are in place, there is no more need to access the front of the car, so the bumper cap is reinstalled. If you're a belt-and-suspenders sort of guy, you might want to leave the bumper cap off until the end. This way any electrical or plumbing troubleshooting goes easily.

There was a bit of the dragster feel to the Bullitt thanks to its stone-stock suspension and standard brakes. Like all of the fairly massive positive-displacement superchargers, the Edelbrock added a bit of weight over the front axle. Thus, the Bullitt rears up under the big torque and settles down noticeably when you get off the power. The stock brakes aren't optimum for extended use with supercharger power either, but that's no mystery. We suggest upgraded brake pads, or better yet, larger front brakes to match a blower installation. A touch more spring rate would be good, too, but it's difficult to find a spring with a little more rate and no lowering.

Curiously, we noticed a distinct notch in the Bullitt's power delivery in Second gear. Up to 2,500 rpm the power was a hair flat, then it would switch on, charging powerfully up the tach. The pull in the other gears didn't have this notch in it, so it may be a Bullitt tuning issue or some other Ford artifact in the software. This is just the sort of thing that prototype and early production cars exhibit, so we'll bet it's gone by the time you read this. Edelbrock says none of its Mustang GT test cars have exhibited this notch.

All said, what a great street car. The combination of ample extra power delivered on demand is tough to beat.