A flap in the exhaust just after the turbo that the drive can engage manually to slow down the exhaust gas flow, thus slowing the engine down and in turn, slowing the transmission and drivetrain down, to assist the actual brakes.
The brakes started to fade when we were tankin it down the estate so I flipped the exhaust brake on so I could get round the corner without rolling the truck over on to the orphanage.
by Xboxmad July 6, 2015