Frank H. Cicerale
November 1, 2008

The Roush Connection
We headed to JDM Engineering to cover the Roushcharger TVS install on a Roush 428R Mustang. Before we get into the details of the installation, we chatted with Bunn about the specifics of the kit Roush offers, and some things of interest that we had questions on. "We offer three different versions of the Roushcharger TVS kit," Bunn says. "The kit that we sent to JDM Engineering for the installation was a kit we have for naturally aspirated, Three-Valve engines. It comes with everything needed to install the blower on a naturally aspirated engine, from the blower to the intake manifold, hardware, intercooler, and more. The second version of the kit is the one we sell to those who already have a Roushcharger on their car, such as the 427R, 428R, or the Stage 3. This is a bare-bones kit that replaces the blower and intake manifold with the TVS pieces. Nothing else is needed because the car already has all of the other paraphernalia associated with the super-charger. The last version is actually a complete short-block with the blower kit. This is essentially the same package that we installed in the P-51A Mustang, and allows you to run higher boost levels with the TVS due to the P-51A's specific engine components. With the P-51A, we change the components to forged pieces, and lower the compression ratio from 9.8:1 to 8.5:1."

One thing that Bunn noted was the fact that a tune is needed with the TVS installation. "We currently don't offer a calibration for the naturally aspirated or swap kits," he says. "When we sell these kits to our customers, we tell them that they must take the car to a professional shop, such as JDM, to be tuned. We also suggest that they go through the bottom end and beef it up, though Jim [D'Amore of JDM Engineering] seems to have a good handle on making a stock bottom-end motor live with a TVS making a respectable amount of boost. As for the P-51A short-block kit, we do offer a tune with that one."

Roush also offers everything in the kit to make the installation a snap, though a few fuel-system and ignition upgrades are recommended. "We recommend it, but make it a point to almost tell the customer that a GT500 fuel pump is needed," Bunn says. "The content of the kits are unique in that most everything is there, including a dual 60mm throttle body similar to the one seen on the GT500, as well as a more durable and better flowing cold-air kit. As for the ignition system, we recommend a one-step-colder plug for '07-and-older cars, while the '08-and-newer vehicles can retain their stock spark plugs. In 2008, Ford went to a 5/8-inch plug, which is smaller than the '07s'. The smaller plug seen in the '08 is more resistant to detonation under boost than the '07-and-prior plugs due to the design."

Price And Performance
So what does this all mean in terms of price and horsepower? Let's get the pricing out of the way first. For the full-on kit (such as the one we installed), the TVS and its related components will set you back $5,899 and can be found in the Roush catalog or online under PN 403994. For those who already have a supercharger, such as the Roushcharger, the kit checks in at $4,999 (PN 403995), minus all of the unneeded components that the big kit comes with. While that's a good chunk of change, based on our before-and-after dyno and track testing, it's well worth it.

The car on which we performed the swap was an '08 Roush 428R Mustang equipped with a five-speed transmission. It was probably better we tested it on a car that already had mods done to it, as most of you out there don't hesitate to throw the bolt-on speed parts onto your S197s. Regardless, our test subject showcased a full-on Kooks exhaust system, including long-tube headers, as well as adjustable rear shocks, instant center brackets for the control arms, 4.10 gears, a one-piece aluminum driveshaft, and 15-inch Bogart rear rims wrapped in 275/60/15 Mickey Thompson drag radials.