Cummins Diesel BD Exhaust Brake

Stainless Steel Exhaust and More Braking Power

Jason Thompson
Feb 1, 2012
Photographers: David Kennedy
Since this Cummins doesn’t have a throttle valve on the intake (like most gasoline engines), there is little engine braking or negative torque created by the crankshaft. This is because the traditional diesel engine doesn’t have to fight vacuum pressure, which creates pumping losses for non-direct injection gas engines. Our diesel engines get to take unobstructed breaths, which creates efficiency. Therefore, when towing heavy loads with our ’99 Dodge Ram (before the installation of the BD exhaust brake PN: 2033137), we relied too much on our friction brakes. This exhaust brake modification takes about a weekend’s worth of time, although it could take longer if the Cummins engine is ’98 and older, since it will require stiffer valvesprings. In the end, the effort and money was well worth it because it made our older truck perform just as good as a new one.
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Thermal Management and Stainless Steel
According to BD, the exhaust brake can also help keep your valves from warping. This is because when an engine goes uphill, it gets really hot. When it crests the hill and starts to go back down, the valves get very cold. The exhaust brake can actually help make the temperature difference not so dramatic. The other part of this project was the installation of the MBRP stainless steel exhaust. It increased the general morale of our seasoned hauler with its good looks. Another benefit is the free-flow design, which is thanks to the mandrel bends and larger diameter. This creates less backpressure. MBRP claims a 1 to 2 mpg and 18hp increase compared to the stock exhaust system.
Exhaust Brake Types
There are three types of engine brakes. The first type, invented by Clessie Cummins and developed by Jacobs Vehicle Systems, is common for over-the-road trucks. It’s an internal type that uses the engine’s valves to create negative torque at the crankshaft. The next type is the external style, like BD’s, which restricts exhaust gas after the turbocharger. The newest version uses the variable vane on the turbocharger to restrict flow. The following quote is what first inspired these inventions:
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“About dusk on the fifth day, we reached the top of Cajon Pass west of Barstow, California. Before retiring to the sleeping compartment, Dave had warned me against this 35-mile stretch of mountainous downgrade. I failed to register when the sign for the Cajon Pass appeared. Soon, however, I realized my error. The brakes wouldn’t hold. Now running in Third gear, I tried desperately to get into a lower speed. Nothing doing, I saw I would just have to ride it out. I suddenly saw something moving across the road ahead. I realized with new alarm that a freight train was cutting across our path. As we raced inexorably toward the crossing and doom, the train’s caboose loomed out of the darkness. Its red lights cleared the highway just as we reached the tracks. We had escaped certain death by inches.”
— Clessie L. Cummins (during a 1931 truck speed record attempt from New York to Los Angeles)

Sources

MBRP Performance Exhaust
N/A, AK
888-636-7223
www.mbrpautomotive.com
BD Diesel Performance
Sumas, WA 98295
800-887-5030
www.dieselperformance.com

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