To combat these niggles, BD manipulates several areas of the engine-control software. The BD brake controller taps into the factory backpressure sensor that controls the EGR and VGT function, providing it with the appropriate backpressure value. The vehicle's factory throttle-position sensor (TPS) is used for precise exhaust-brake activation, while the vehicle-speed sensor (VSS) is used to turn the brake off at speeds too low to create effective engine braking. Finally, the BD brake controller monitors the cruise-control input. "If we didn't do this, the brake would apply when the cruise control was activated and the throttle was released," Parker says. "The cruise control would be trying to fuel the engine while the brake was trying to slow it down. So when the exhaust brake is activated, it automatically disables the cruise control."
On 6.0L Power Stroke applications, the BD brake mounts in the vehicle's exhaust system and is activated using an integral air cylinder and onboard air compressor (included with the kit). When the signal to activate is received by the BD exhaust-brake controller, the compressor is energized and the control solenoid opens, allowing the air into the cylinder to close the exhaust brake. The BD brake incorporates a butterfly valve shaft that is offset so the surface area on the upstream side of the valve is larger than the downstream side. In this way, the exhaust pressure can push against the air pressure in the cylinder to regulate the backpressure. The higher the air pressure in the air cylinder, the higher the backpressure. In this application, the user adjusts the air cylinder to achieve a maximum of 45 psi of exhaust backpressure (the factory-specified maximum) at peak braking rpm-usually set just below engine redline. And because the system is activated using a pressurized air cylinder instead of a vacuum, exhaust-brake effectiveness won't diminish at high altitudes.
 The weld joints are sprayed...  The weld joints are sprayed with corrosion-resistant paint, then a band clamp is added on the discharge side of the exhaust brake. A leak-free weld is important on the upstream side because this is where the exhaust pressure builds. Downstream, the flange can be tack-welded and secured with the supplied band clamp. |  The onboard air compressor...  The onboard air compressor and related equipment are located under the hood on the passenger side. The bracket on top of the HVAC box is the pressure regulator, which controls the brake pressure and is attached to a pressure switch that controls the compressor's function. The line from the brass T-fitting runs down to the compressor itself. The mounting brackets are specific to each application to achieve the correct fit. |  Wiring and air lines from...  Wiring and air lines from the underhood components are routed along the passenger-side framerail and wrapped in a wiring loom (save for the preexisting blue wire on our subject vehicle that is routed to another accessory). These will be attached to the frame-mounted control solenoid and brake valve. Also note the air line with the yellow tip-it's the vent line for the air cylinder that admits/releases air as the cylinder cycles. It will be routed to a location under the hood, away from moisture and dirt. |
 The control solenoid is mounted...  The control solenoid is mounted on the framerail adjacent to the brake assembly to allow for faster exhaust-brake actuation. The wires run to the brake controller, and the air lines run up to the regulator in the engine compartment. |  The exhaust-brake controller...  The exhaust-brake controller is mounted underneath the dash to keep it dry and to facilitate adjustment of the brake-actuation set point. |  The BD Autoloc module is a...  The BD Autoloc module is a waterproof enclosure designed for underhood mounting. Here, it's attached to the top of the fuse box using hook-and-loop tape. |