For more than fifty years, engine manufacturers have relied on the Jacobs’ Engine Brake, commonly called a “Jake Brake.” All Jake Brakes come fully integrated into the engine and are an essential component in slowing and controlling your big rig. The Jake Brake has made it significantly easier and safer to drive on a steep mountain or slippery road with a commercial motor vehicle.
To fully understand how an engine brake works, you first must understand how the engine operates without the brake, and the 4 phases that comprise it: intake, compression, expansion and exhaust. During a normal 4-stroke diesel engine cycle, the intake valve will open, and the cylinder will fill with air. The air will then be compressed at high pressure and expand, thereby pushing the piston down and returning energy back to the engine. The movement of the piston coming back up will then push the gasses through the exhaust system and out of the vehicle. Since very little energy is absorbed by the engine, drivers need to rely on their service brakes to slow their vehicle.
However, by using the superior slowing capabilities of the Jake Brake, drivers will spend less time off the road and experience improved total cost of ownership such as greater fuel economy, reduced service brake maintenance and greater up time, enhanced vehicle control and higher productivity, which leads to shorter trip times.
To use the Jake Brake’s engine slowing capabilities, simply remember three things: switch, clutch and throttle. Set the switch to the appropriate load setting, release the clutch pedal, and remove your foot from the throttle. These controls will ensure a safe and manageable control speed by transforming your power producing diesel engine into a power absorbing air compressor. Just remember that the Jake Brake is a vehicle slowing device, not a substitute for the service brakes. The rig’s service brake still needs to be applied to bring the vehicle to a complete stop.
When you have your Jake Brake installed, notice how similar the two cycles are; the major difference, however, lies in the valve timing. While the intake phase will remain the same, by opening the exhaust valves near the end of the compression stroke, the energy used to compress the air in the cylinder is not returned to the engine and is released to the exhaust system. By utilizing the engine to absorb energy, the truck’s downhill speed can be controlled. And with new emissions technologies, the sound of the Jake Brake operating is all but eliminated.
Some drivers prefer to leave the Jake switch on constantly and others turn it on and off as it’s needed. The Jake Brake is a great tool; you have to be a little more careful when you’re on slippery roads. But even in slippery road conditions, the Jake Brake is an additional tool that can help you slow down and come to a complete stop. If you’ve got your rig lined up straight the Jake Brake will keep your truck from jack-knifing. Of course, keep in mind that if you’re on glare ice there may not be a way to stop, even with the Jake Brake functioning.
There’s a right way – and a wrong way – to use a Jake Brake. Here are a few tips to keep in mind when using your rig’s Jake Brake.
- Make sure your engine is warm before you use the Jake Brake; it should be 150° or higher before you turn on your Jake Brake switch.
- Never use the Jake Brake if you’re low on oil.
- In order to protect your engine, use the Jake Brake only in the lower RPM.
- The sweet spot for using the Jake Brake is in the shifting zone, between 1,100 and 1,300 RPM.
The Jake Brake is an important feature that professional drivers need to fully understand and operate correctly in order to ensure safety.
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