Engine Brake

I just finishef the section on air brakes of the high road training. It was the toughest section for me so far. I am completely baffled by this engine brake. Can someome explain to me how this works.

Thanks Jordan

Certainly.

Engine brakes work by restricting the flow of exhaust out of the engine. While the engine is trying to push the exhaust out, the "Jake Brakes" as they're referred to restrict the flow of exhaust gases which puts pressure back against the engine - slowing it down.

You wouldn't think that simply restricting the flow of exhaust out of the engine would be able to produce a whole lot of force, but it's incredible just how much force it produces. If you're in the proper gear and the engine RPM is in the high end of the range, you can take a 78,000 pound truck down a long, steep mountain by using the Jake Brakes alone - you won't have to touch the brake pedal at all. That's how much stopping force it produces.

The higher the engine RPM, the more back pressure the Jake Brakes produce, therefore the more effective they are.

One time I had a driver say to me "I don't know why they even bother putting Jake Brakes on the truck. They don't do anything. They just make noise."

Nobody ever told that driver you have to be in the higher end of the RPM range for them to be effective. I'm sure it was a tremendous surprise to see how powerful they were the next time he used em!

Wow. Thanks. That seems like a lot of force if you don't have to use service brakes at all.

Thanks

During my two weeks OTR with a Trainer, I saw this with my own eyes. We were starting to go down (I think it was Cat Mtn?) a 6% downgrade in Eastern TN on our way to Atlanta. The Trainer put the truck in 8th gear with the Engine Brake engaged. He never had to touch the service brake on the way down. The Jake Brake held us at 35 mph and no higher than 1500 rpm all the way down. Other trucks were smoking the brakes to hold down their speed and their drivers probably had high "pucker" factors, but we were relaxed and stress free all the way down the mountain. It made a believer out of me as to how beneficial engine brakes can be.

During my two weeks OTR with a Trainer, I saw this with my own eyes. We were starting to go down (I think it was Cat Mtn?) a 6% downgrade in Eastern TN on our way to Atlanta. The Trainer put the truck in 8th gear with the Engine Brake engaged. He never had to touch the service brake on the way down. The Jake Brake held us at 35 mph and no higher than 1500 rpm all the way down. Other trucks were smoking the brakes to hold down their speed and their drivers probably had high "pucker" factors, but we were relaxed and stress free all the way down the mountain. It made a believer out of me as to how beneficial engine brakes can be.

If you were on I24 that would be mount eagle.

Yup...Mount Eagle can be horrid, if you head down in to high of gear, which alot of drivers seem to do. The old wives tale of " you go down the mountain in the same gear that you go up it" is basically "bovine excretment". No mountain has sides exactly the same. It takes experience, and knowing what your loaded weight is, and how your truck handles it, to let you put it in the right gear, and walk down the mountain on your "Jake aka Engine brake". Different trucks, with different transmissions, engines, and rear gears will all go down the mountain differently, with the same load on them. 35mph is a reasonable speed to go down nearly all the mountains in the US. But remember...you can go down mountains to slow for the rest of your life,,, you can go down a mountain to fast just once.........

But remember...you can go down mountains to slow for the rest of your life,,, you can go down a mountain to fast just once.........

Reminds me of the old saying..there are old cowboys and bold cowboys, but NO old, Bold Cowboys...

But remember...you can go down mountains to slow for the rest of your life,,, you can go down a mountain to fast just once.........

Reminds me of the old saying..there are old cowboys and bold cowboys, but NO old, Bold Cowboys...

and if you want a really good lesson..listen to Harry Chapin singing,"30,000 pounds of bananas"...

OK Guy...ya got me curious...off to Youtube I go to find Harry Chapin......

Just listened to it...funny...but I like Cats in the Cradle much better.....