Unlike gasoline engines, diesel engines produce no vacuum when the throttle is released to help reduce the speed of a vehicle. The diesel’s higher compression acts like a spring on the crankshaft, even with no fueling. An exhaust brake restricts the exhaust, making the pistons work harder, slowing down the crankshaft and the truck.
Driving an engine-powered pickup, SUV or motorhome gives the idea that there is precious little braking effect upon backing off the throttle pedal. Few things can be more terrifying to someone driving a heavily-loaded vehicle: pulling a trailer in a long downhill grade that progressively overpowers the vehicle's braking system as the driver struggles to keep downhill speed in check. When the vehicle's brakes overheat and can no longer do its job, continued operation will only make the brakes hotter, further reducing its effectiveness. The driver, clearly terrified, is now losing control of the vehicle. Speed continues to climb and there's little or nothing the driver can do about it –at least not now that's he's already caught up in this tight spot.
Even when a vehicle's brakes are capable of keeping the vehicle from gaining unwanted speed downhill, certain cargoes inflict significant brake wear and leave a little safety margin for additional braking. Sustained brake use can cause overheating that will damage several braking system components, such as the brake rotors.
Generally, a vehicle's brakes simply aren't up to the challenge of sustained heavy braking. Conventional brakes are, after all, simply mechanical devices designed to convert kinetic energy (the vehicle's movement) into heat energy, thus, speeding down the vehicle. This is typically accomplished by forcing stationary friction surfaces (either brake shoes or brake pads) against a rotating machined metallic surface (either a brake drum or a brake rotor) coupled to wheel rotation. The more pressure with which the friction surfaces are applied against the rotating surfaces, the more heat is generated therefore, greater breaking effect. This is so far so good; but both the friction surfaces and the rotating surfaces have temperature limits at which it will begin to fail. The rotating brake drums or rotors can become literally incandescent, approaching the point at which the metal begins to lose structural integrity. Similarly, the stationary friction materials can get so hot that the composite material binding the friction materials together actually melts and begins to boil, releasing a thin layer of liquid binding material and hot gases that form a lubricating boundary barrier between the friction materials and the brake drums or rotors. When this happens, breakage ceases to takes place and a phenomenon known as "brake fade" occurs. Under these conditions, continued brake application does little or nothing to slow the vehicle. Fortunately, there are things that can be done to upgrade the braking systems that are standard equipment on many trucks and RVs.
Traditional brake upgrades consist of installing bigger brakes (an expensive procedure, at best) or adding special friction materials (if they are available for the vehicle) that are sufficiently capable of providing higher sustained operating temperature before brake fade occurs. While both of these approaches will increase braking capability, one of the most practical techniques is to utilize supplemental braking capability to take some of the load off the conventional brake system.
Typically, drivers downshift to a lower gear to provide some supplemental breaking, allowing the engine to exert some braking force as the engine attempts to intake air against a closed throttle. This only works, of course, on gasoline engine-powered vehicles that have air throttles. Drivers with diesel engines, which have unrestricted air intake, face a different problem. Diesels provide little engine braking unless it is fitted with either an internal or an external device that uses the pumping action of the engine to do the work. In either case, such devices on diesel engines are intended to create a pumping resistance that results in engine braking.
The internal mechanism built into some large diesel engines is called a Jake Brake®. It is named after Jacobs Vehicle Systems®, the one who instigated it. This mechanism opens the exhaust valve of each cylinder at the top of each compression stroke, thus, the engine has to work to compress the air, which is then released into the exhaust system. Unfortunately, the operation of Jake Brakes is fairly noisy, usually making a loud burbling sound as the vehicle decelerates. This is a fairly complex and expensive system that is commonly found only on large trucks or some large motorhomes. It is also something that cannot be retrofitted to a “non-Jake Brake diesel” since it is incorporated into the engine’s original design.
An external supplemental exhaust braking system for diesel engines can economically be retrofitted to the vehicle’s exhaust system, thus, the name “exhaust brake”. Such a device partially closes the diesel engine's exhaust when the throttle is released. This is completed by placing a shut-off valve in the exhaust system downstream from the engine. The valve uses an actuator to lock it against exhaust flow, forcing the engine to pump against a restricted exhaust to create braking resistance. Such devices are easily retrofitted to diesel trucks and motorhomes of all sizes. An exhaust brake upgrade can actually pay for itself in reduced brake wear and maintenance over the life of the vehicle. Best of all, periodic service or replacement is not required in a well-designed exhaust brake.
Exhaust brakes have a lot of effective befits on diesel-powered vehicles. It can provide engine braking to assist deceleration, help control downhill vehicle speed, reduce brake heat, reduce brake wear and provide a greater braking reserve for the conventional brake system. It is relatively quiet in normal operation and use. These benefits, nonetheless, are as effective as explained when the exhaust brake system is set, which is at the discretion of the driver.
The operation of supplemental exhaust brakes varies in the design. Most brakes are very basic, using a simple on-off switch to trigger a solenoid or a vacuum actuator to close the exhaust brake valve —essentially an all-or-nothing braking device. Some designs create an exhaust restriction even when not activated, negatively affecting both performance and fuel economy. Other designs are more sophisticated. Gale Banks Engineering manufactures an exhaust brake, the Banks Brake, based on a unique design that enhances exhaust flow for power benefit and better fuel economy under normal driving conditions. The Banks Brake is also the industry’s only computerized exhaust brake, featuring the exclusive computerized brake controller (CBC) module. The CBC functions automatically when the system is turned on, calibrating throttle pedal location, “exercising” the valve and providing fast engine warm up on cold starts and improving throttle response after brake activation. The Banks Brake also produces more braking force than other designs provide when activated. For Dodge and Ford diesel vehicles with automatic transmissions, Banks also offers an optional electronic device called the SmartLock™ that automatically locks the torque converter clutch at a specified point and raises transmission line pressure while braking, therefore, providing better holding capacity. By preventing excess slippage, the SmartLock also lessens transmission fluid temperature while braking, which greatly prolongs transmission life. GM and Chevrolet ’01-’03 Duramax diesel trucks already have a similar acting Tow/Haul feature built into their automatic transmissions and do not require the SmartLock module.
A well-engineered exhaust brake also includes defense and protection to prevent any excessive exhaust system overpressure that might harm the structural integrity of either the exhaust system or the engine valve train. Unfortunately, not all exhaust brakes are created equal. There are designs that bypass so much exhaust flow that they provide little or no braking effect in some circumstances. Still other designs restrict or disrupt exhaust flow downstream from the turbocharger, impeding performance during normal driving. Premium designs, such as the Banks Brake, combine both system safety and reliability with effective supplemental braking capability while simultaneously increasing normal driving performance. Diesel-Power Direct, however, promises to provide the best and most beneficial exhaust bake systems to its customers. Not only do customers get excellent vehicle upgrades, they also get the best price. Our site offers low price yet genuine exhaust brakes from manufacturers that strive hard to provide the market with efficient and long lasting vehicle parts and accessories.
An exhaust brake should be considered as a worthwhile safety enhancement for any diesel-powered vehicle and a virtual necessity for vehicles particularly when vehicles are heavily-loaded or towing trailers. It is known that adequate braking is very important, so the quality and features of a supplemental brake should be a prime consideration when purchasing such a device. Think that there’s no need for an exhaust brake? Think again! Yes, there weren’t any problems before but how about in the long run? What about the risks not having an exhaust brake? After all, nobody wants to discover the problem when they’re only part way down a long grade, gaining speed and their vehicle's brakes aren't up to the task at hand (er, at foot). The extended brake life an exhaust brake can provide can help minimize if not avoid vehicle maintenance and give greater peace of mind.
Exhaust brakes are ideal for towing applications such as pulling RV fifth wheels and horse trailers. The Jacobs Exhaust Brake is especially popular with owners who drive in hilly and mountainous regions for the added control on steep grades. |
