"The swap was fairly easy to perform," says JDM's Jim D'Amore. "This car was a bit easier because it already had a supercharger on it. If we were to install this on a stock Three-Valve, it would take one full day. For a car like this, with it already having the intercooler installed and plumbed, it would probably be three hours less."
With the original Roush blower and the added bolt-on parts, and stocked with a custom JDM tune, the Roush 428R thumped out 386 rwhp and 366 lb-ft of torque, also measured at the rear wheels. After spending the day swapping over the blower, D'Amore revised the tune to his liking and strapped the beast to the dyno rollers. When the computer spit out the numbers, we were all duly impressed. The blower increased power by 160 hp to 546, and torque by 183 lb-ft to 549 lb-ft at the rear tires. Also, if you look at the torque curve on the supplied graphs below, you'll see that the boost curve for the TVS blower is smooth and linear, while the same curve for the Roushcharger on the car dipped badly early on and was choppy throughout the entire dyno run.
So how does this translate to the track? Before the blower swap, the quickest this S197 made its way down the quarter-mile was an 11.84 at 119 mph at Epping Dragway in New Hampshire. That was before we got hold of it, however. With the blower on, the car tuned up, and the M/Ts ready to go, MM&FF editor and resident car jockey Evan Smith slipped behind the wheel for a couple of stabs at the Old Bridge Township Raceway Park quarter-mile in Englishtown, New Jersey.
In this diagram, you can see...
In this diagram, you can see the changes Eaton made to the inlet side of the TVS as compared to the Fifth-Generation M122 blower. (Diagram courtesy of Eaton Automotive)
Here's a dyno graph of the...
Here's a dyno graph of the "before" testing. Power is admirable at 386.13, with torque checking in at 366.78. If you look at the torque curve, though, you can see the noticeable dip early on in the dyno run, and how choppy it is the entire way through.
The key to the TVS making...
The key to the TVS making more power at lower boost levels revolves around the efficiency of the blower as compared to the M122. Here, you can see how much cooler the TVS is compared to the M122. Cooler thermal efficiencies lead to lower air inlet temps and more power. It's as simple as that.
The temperature showed 90 degrees on the thermometer, humidity was at 80 percent, and there was a 10-mph headwind-obviously not the best conditions in which to go for low elapsed time and top speed. The first two runs resulted in high-1.9-second 60-foot times, and an 11.73 on the first run and an 11.85 on the second at close to 124 mph. Obviously, Revvin' Evan knew there was more in the car, even on this sweltering summer day. "The Roush had wicked throttle response and was blowing the tires off badly, on launch and in Second," he says.
After cooling down the blower, Smitty lined up for the final three runs the car would make that day. The results were astounding. The next two runs showcased 60-foot times in the low-1.8-second zone, and a pair of 11.58-second elapsed times. The trap speed shot up to 122.93 and 123.62, respectively. The final run of the day saw the best short time so far, a 1.76, but a bit of heat soak set in, and the car slowed to a respectable 11.66 at 119.96. Smith feels that with a drag suspension and favorable weather, the Roush would be a 10-second machine.
While the quarter-mile testing didn't show the true potential of the car, we can chalk that up to the tight suspension and poor weather conditions. Still, with horsepower numbers like that, there's no question as to the benefits of the new TVS supercharger. Welcome to tornado alley!
While the power increase with...
While the power increase with the TVS is astounding in itself, even more amazing is the smooth and linear torque curve. At the rear tires, the Pony kicked out 546.33 hp and 549.59 lb-ft of torque-an increase of 160.20 rwhp and 182.81 rwtq. The torque curve is smooth throughout the entire dyno run, and the dip that was there in the "before" graph has disappeared.
With a best lap of an 11.84...
With a best lap of an 11.84 at 119 miles per hour before the swap, MM&FF test pilot Evan Smith banged gears in the Roush at Old Bridge Township Raceway Park. On a less-than-ideal day, the Mustang rolled to an 11.58 at 123 mph. That's an improvement of 0.260 second and 4 mph. Imagine what the car could have run if the weather conditions were ripe for making gobs of horsepower.