If you have ever pulled a heavy load to the top of a mountain, then you know what it's like trying to maintain control of your speed while going downhill. The weight pushes your rig faster and faster until you pass a runaway truck ramp and realize the next corner is marked with a 35-mph sign. Whoa, baby. Or maybe you traversed a steep downhill stretch of road that has switchbacks with tight corners until your brakes finally fade away and the only thing you're left with is a sinking feeling in your stomach and a desire to stop. Losing your brakes is a hair-raising experience. Downshifting the vehicle does not always help much on the really steep hills.
Unlike a gasoline motor, which controls the speed of the engine by regulating the intake mixture of fuel and air with a butterfly in the air passageway, a diesel motor regulates the speed by only controlling the fuel entering the engine. A diesel engine's air intake is unrestricted, and backing off the throttle does not restrict the air flowing into the motor to help create a vacuum as it does in gasoline engines. Large diesel trucks are equipped with an elaborate exhaust brake, a Jake Brake. Exhaust brakes for smaller diesel engines work on a similar principle, but are much quieter than a Jake Brake on a semitruck.
The exhaust brake concept is simple. The escaping exhaust gases are restricted with a flat piece of steel mounted on a shaft inside the exhaust system. When the shaft is turned, the butterfly valve blocks the escaping exhaust gases and they back up into the combustion chambers of the motor. This creates resistance and slows down the motor. A slower-running motor translates to a slower-moving vehicle. The backpressure does not harm the engine, and the only noise that can be heard is a soft hiss from the exhaust gases escaping through a small relief hole in the butterfly valve. It has the same effect as lightly pushing the brakes, but without any wear on the brakes. The faster the engine is turning, the more backpressure builds up, and the more slowing effect there is on the vehicle. Exhaust brakes are a supplemental braking system and are not designed to stop a vehicle.
Gale Banks Engineering, which pioneered the use of turbochargers to increase the efficiency of diesel motors in the light truck market, has developed an exhaust brake that when activated not only slows the vehicle down but by virtue of its design also increases power by as much as 30 hp when it's not being used. The 3-1/2-inch-diameter seamless housing moves the butterfly further away from the turbine than conventional exhaust brakes and makes a gentler bend as it sends the exhaust gases down toward the muffler system. During the testing process, Banks found that even more resistance could be transferred to the ground if the transmission torque converter was locked up and the line pressure increased. This reduction of transmission slippage also lowers the operating temperature of the automatic transmission. To perform this function, Banks developed an electronic controller that automatically handles locking the torque converter and increasing the line pressure when the exhaust brake is activated. Banks dubbed this lockup device a SmartLock and offers it as an option for several vehicles. Our installation concentrated on the installation of the Banks Brake. After installing the new Banks Exhaust Brake on a Ford Power Stroke diesel motor, we loaded up the truck and headed into the San Gabriel Mountains for a testdrive. When the loaded truck came to a downhill section of road, we let off the throttle and activated the exhaust brake by flipping the on/off toggle switch on the dash. Instantly, the 12-volt vacuum pump motor began running and the vehicle started slowing down. The pump provided vacuum to an actuator and it closed the butterfly in the exhaust brake housing. Backpressure began building up in the cylinder combustion chambers. A soft hissing noise could be heard as the exhaust gases escaped through the relief hole in the butterfly valve and the truck began to slow down. As expected, at higher rpm, the effect was more dramatic. It felt as if we were riding the brakes. When more speed was needed, simply pressing the throttle would shut-off the vacuum pump, open the exhaust valve, and the truck would accelerate. With the exhaust brake switch still in the on position, releasing the throttle reactivates the exhaust brake system. Its wiring harness is also tied into the cruise control, which keeps it from coming on when the Banks Brake is engaged. We began looking forward to coming across steeper downhill sections rather than dreading them.
The installation of the Gale Banks Exhaust Brake System did not require any special tools beyond those used by most backyard mechanics and should take about four to five hours to install. However, a 12-point 8mm socket on a swivel head ratchet will make life easier when you remove the bolts on the turbine and install the exhaust brake housing in the small space at the rear of the motor.