Rotary engines make a sound that’s unique among combustion engines. The noise is like a dentist’s drill channeled through an amplifier with the volume turned up. In this video, enjoy the cacophony has Rob Dahm’s custom RX-7 races mildly tuned Jeep Grand Cherokee Trackhawk.
There’s not much Mazda left in this RX-7. The engine is now a four-rotor setup with a massive 94-millimeter turbo supplying the boost. The total output is as much as 1,330 horsepower, but Dahm backs down the output to 1,000 hp for reliability.
This RX-7 is all-wheel drive. Dahm can tune it to have all the power going to the rear wheels or as much as 50 percent turning the front axle. There’s a sequential gearbox.
In comparison, the tune on the Grand Cherokee Trackhawk is fairly mild and functions as a daily driver. A tune to run on E85 boosts the output to 850 hp, versus the stock 707 hp. It rides on an aftermarket set of five-spoke wheels and Eibach lowering springs.
The racing starts with a 1,000-foot, heads-up race. With more power and less weight than the Trackhawk, the RX-7 scores a victory by several car lengths. However, the Jeep does an admirable job of keeping up off the line.
After the first run, Dahm says he can “taste” carbon. A tire pressure sensor fell off and was rubbing against the wheel.
The second race is 500 feet. The Jeep is supposed to get a slight advantage, but there’s a miscommunication. The result is more of a heads-up run. The Mazda gets loose, and Dahm has to back off the throttle. This lets the Trackhawk score a victory.
Between races, Dahm finds an issue with the RX-7’s front driveshaft. This means the car has to run in rear-wheel drive for the final challenge. Once again, they go 1,000 feet heads-up. The Jeep gets a great start, but the Mazda pulls ahead down the strip. By the end, it’s about three car lengths ahead.
