Exhaust Brake

What Is an Exhaust Brake?

If you've ever piloted a loaded diesel pickup down a long mountain grade, you know the anxiety that comes with relying solely on your service brakes. That's exactly the problem exhaust brakes were designed to solve. An exhaust brake is a device that closes off or restricts the exhaust path from the engine, causing exhaust gases to be compressed in the exhaust manifold and in the cylinders. Because the exhaust is being compressed with no fuel being applied, the engine works against itself — slowing the crankshaft, and by extension, the entire vehicle.

The key reason exhaust brakes matter specifically for diesel engines comes down to engine design. Diesel engines control power output by regulating fuel rather than airflow, meaning they have no throttle plate creating intake vacuum. As a result, lifting off the accelerator in a diesel provides virtually no engine braking — the truck simply coasts. On a heavily loaded rig or while towing a fifth wheel through the mountains, that can quickly become a dangerous situation. An exhaust brake fills that gap, providing supplemental retarding force that can in many cases slow the vehicle on a downgrade without ever touching the service brakes.

Why Add an Exhaust Brake?

The practical benefits of an exhaust brake extend well beyond safety. The primary advantages include:

• Reduced brake heat: Service brakes that overheat lose effectiveness through brake fade — an exhaust brake keeps them cooler and in reserve.
• Extended brake life: Every time the exhaust brake helps manage speed, your pads and rotors get a reprieve, reducing wear and replacement intervals.
• Improved downhill speed control: Especially valuable when towing trailers, hauling heavy payloads, or navigating mountain passes.
• Quiet operation: Unlike compression brakes (Jake Brakes), exhaust brakes are relatively quiet and are not subject to the noise ordinances that restrict compression braking in many jurisdictions.
• Minimal maintenance: A well-designed exhaust brake has no parts requiring periodic replacement and can be retrofitted to most diesel exhaust systems.

Some advanced exhaust brakes communicate directly with the engine's computer to provide precision on-demand braking, while others are completely mechanical — each approach has its merits depending on application and budget.

Top Exhaust Brake Brands

BD Diesel is widely regarded as one of the most recognized names in aftermarket diesel exhaust brakes. Founded in 1972, BD released their first exhaust brake in 1989 for Ram trucks equipped with the legendary 12-valve Cummins engine, and they've been refining the technology ever since. Their signature Variable Orifice Technology uses a solid, offset butterfly valve with spring-loaded pressure regulation to deliver up to 150 retarding horsepower throughout the engine's RPM range — not just at high RPM like simpler designs. BD builds their brake housings from rugged cast iron, with an exclusive alumibronze bushing, piston ring-seals, and a stainless steel butterfly shaft engineered to withstand the extreme heat cycles of the exhaust environment.

Pacbrake brings a legacy dating back to 1961, when the company began supplying exhaust and engine brakes to commercial truckers, loggers, and the military. Their flagship PRXB (Pressure Release Exhaust Brake) line is engineered to deliver maximum braking power starting as low as 1,200 RPM, providing consistent holdback through the entire operating range — a major advantage in the 1,400–1,800 RPM range where most towing occurs. Pacbrake's PRXB brakes feature an industry-exclusive Arcor nitride coating on housing and components for superior corrosion resistance, and the line is severe-duty and military approved, including use in the U.S. Army's fleet of Stryker Wheeled Vehicles.

What to Look for When Shopping

When choosing an exhaust brake, consider your engine platform (Cummins, Duramax, or Powerstroke), transmission type, and whether your truck uses a Variable Geometry Turbocharger (VGT) — since some inline brakes are not compatible with OEM VGT setups. Also weigh whether an air-actuated or electronic actuator system better fits your needs: electronic units eliminate air compressors and the risk of frozen air lines in winter, while air-actuated systems are proven workhorses in heavier-duty applications. Above all, match the brake's pressure regulation design to your typical use case — consistent RPM-range performance is the hallmark of a quality exhaust brake.