Replacing our original semi-automatic...
Replacing our original semi-automatic valve body with the TCI transbrake unit was very straightforward. It involves removing the old valvebody and bolting up the new TCI unit. The TCI transbrake only uses one check ball, located in the rear servo. All others must be removed.
Back in the pits, just as Buck suspected, the air pressure in the Mickey Thompson radials was way too low. Cooler weather conditions caused the pressure to drop down to 12 psi, so we aired them back up to 18 psi. Likewise, since we had never experienced tire shake before, the rear shocks were set at two clicks from full loose. Project Fox's single-adjustable Competition Engineering shocks feature 16 clicks of adjustability, so we tightened them up to eight clicks from their stiffest setting. Furthermore, since we were unsure of how high the TCI transbrake would allow the motor to rev up at the line, we left the timing curve in the MSD box unchanged from our prior test session at Lonestar Motorsports Park. The tune was set to ramp in all the advance back in by 3,500 rpm, and since the transbrake allowed loading the converter up to 3,500 rpm, that meant that we were leaving the gate with all 28 degrees of advance. Just in case the motor was overpowering the tires, we dialed in 10 degrees of retard at 3,500 rpm, and ramped it back in by 5,000 for the next pass.
To engage reverse with the...
To engage reverse with the touch of a button, the transbrake relies on an electric solenoid that takes the place of a standard modulator. It slides into the side of the case, and is actuated by a button in the cockpit.
The tweaks definitely helped, as the tire shake was far less violent on the next pass, and the 60-foot time dropped to 1.72 seconds. A nice improvement, yes, but it was still poor enough to warrant an aborted run. On the next pass, we decreased the launch rpm from 3,500 to 3,000, netting a 10.21 at 137.49 mph timeslip on a 1.67-second 60-foot time. While the tuning changes helped reduce the severity of the tire shake, it wasn't entirely eliminated. The next logical change is to adjust the instant center of the rear suspension. Project Fox's Competition Engineering lower control arm relocation brackets feature three different sets of boltholes, and Buck thinks that raising the rear of the arms from the lowest setting to the center setting will help soften the hit to the rear tires. Unfortunately, our test-and-tune session came to a close before we had a chance to change the instant center, so we'll have to save that for our next round of testing.
A Track In Your Own Backyard
For decades, Hennessey Performance churned out some of the most powerful late-model performance machines in the world. Its fire-breathing Dodge Vipers are what first put Hennessey Performance on the map, but these days everything from LS-powered Camaros and Corvettes to new-age Hemi cars and mod-motor Fords fill its 30,000-square-foot facility. A cool 1,000 rear-wheel horsepower is very much the norm at this joint. The kicker is that testing these beasts out at the dragstrip requires just a 500-foot drive through the parking lot. Like every hot rodder has fantasized about-John Hennessey has his own dragstrip in his backyard. He acquired Lonestar Motorsports Park several years ago-located 45 minutes west of Houston-and built a brand-new shop right on the same facility. Hennessey has already expanded the track to a full quarter-mile, and is also putting up a new road course and karting track. Lonestar Motorsports Park hosts regular test-and-tune nights and special events, and as we found out during our test session, the place hooks hard. The one-two tandem of a premier performance shop combined with a dragstrip make Hennessey's impressive compound one of the most unique facilities in the country. For anyone in the Houston area, it's definitely worth checking out. -Stephen Kim