Nerd’s Eye View: SEMA 2014 Part II


A common accessory on diesel trucks doing a lot of towing is an exhaust brake bolted to the exit of the turbine housing.
It’s a heavy duty butterfly valve that acts as a huge potato in the tailpipe to backpressure the engine which creates more engine braking power.
This is a basic setup from Pacbrake. An air compressor keeps the air storage pressure cylinder above a minimum pressure. When the driver demands the exhaust brake to turn on, the pressurized air in the cylinder powers the pneumatic actuator to open and close the exhaust brake valve. So how much braking power does the exhaust brake add? On a Dodge Ram 4500 HD, braking power from the factory VGT turbo alone is about 150hp. With the exhaust brake added, the braking power nearly doubles to ~280hp. For you guys with diesel tow setups, an exhaust brake is definitely something to consider if you’re towing up and over mountain passes. I can only image how big of a pucker factor it would be for the brakes on a truck and trailer to fail on a long descent.
Switching to a completely different type of turbo 6 is this Chevy Indycar engine with a pair of Borg Warner EFR turbos.
The clutch is small diameter requiring many disks to contain the torque of the engine. Integrated with the clutch is a toothed wheel with the sensor to measure it mounted at 12 o’clock. Notice the toothed wheel has a few teeth missing at the 10-11 o’clock position. I imagine this allows the ECU to determine the crank position.

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