The 2018 Dodge Challenger SRT Demon ushers in the couple of firsts for production ...
The 2018 Dodge Challenger SRT Demon ushers in the couple of firsts for production cars, and today, we are here to take the look at two of them in greater detail.
Both a transbrake and the torque reserve system are production vehicle firsts and they help the Demon launch with incredible force at a dragstrip.
Our host Jason Fenske of Engineering Explained breaks down both systems to help understand what is actually going on to ensure the Demon has the optimal amount of torque on tap for every quarter-mile run.
It all starts with a torque reserve. The system effectively holds onto 8 psi of boost from a 2.7-liter supercharger by closing off a supercharger’s bypass valve.
The supercharger is always spinning at the rate that depends on engine rpm because it doesn’t have the clutch disconnect. By closing off the bypass valve, the air is not recirculated and it is on reserve for a launch instead.
From there, a fuel flow and spark timing are retarded to allow a system to hold the engine between 950 and 2,350 rpm. But, something has to hold the vehicle back from actually moving before the driver launches the vehicle, right?
That is where the transbrake comes in. The transbrake locks three clutches in the first gear and one clutch in second gear in a 8-speed automatic transmission to hold the vehicle in place ahead of the launch. The driver does not have their foot on a brake with the transbrake engaged.
The driver instead modulates the throttle between a previously mentioned 950 and 2,350 rpm and holds onto the shift paddle.
Since two gears are being held in a transmission, the vehicle does not move and it prevents the reserved torque from making its way to the rear wheels.
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