How does an exhaust brake work?

[TurboDiverArt]

Hi All,

I've seen the diagrams so I think I understand what it's doing. Is it basically giving the engine constipation by stopping it up with exhaust? I'd think that by increasing the exhaust pressure between the turbo and brake, the turbo compressor would stall and would also increase the exhaust pressure in the headers. Is it making the engine harder to turn because you can't get the exhaust out of the engine? Being harder to turn it'll cause a lot more de-acceleration when you engage the exhaust brake.

Is this what it's doing? Pretty cool. I assume the big rigs use these? Is this at all related to sound many 18-wheelers make when they de-accelerate, the loud exhaust popping when they let off the gas?

Thanks,
Art.

[MAV]

The big rig Jake Brake as its called is totally different than the flapper style the pick-ups use. I drive a 2002 Frightliner Columbia with a series 60 Detroit Diesel and our Jakes are mounted on the engine itself. It controls the valves directly. This type of jake is every effective. In 7th gear I can hold back 77,000 lbs at 35-40 mph on a 6% grade with out ever touching the brakes. Thats excellent. Some of the newer Freightliners we have do have the new Mercedes Diesel and this engine has an exhaust brake mounted in the pipe like a pick-up. They all bitch that it doesn't work worth a crap...at least on a semi. It does work well on a pick-up though. This type of brake just makes a hissing sound. The engine mount Jake Brake is a little louder.

[CleviteKid]

Maverick is, of course, correct that the Big-Rig Jake Brake is different than the exhaust flapper.

What many people don't know is that the Jake Brake was invented by Clessie Cummins, founder of the Cummins Engine Co., after the bankers threw him out of his own company. The Jake Brake acts directly on the valves to convert the engine into an air compressor, and after compression of air on the compression stroke, it pops the exhaust valves open to dump the compressed air, so it does not re-expand and push the pistons back down. What you hear is the high-pressure air dumped into the exhaust manifold, and rattling the pipes and muffler.

Cummins convinced the Jacobs Company of drill chuck fame to produce the Jake Brake, and it was only Clessie's reputation in the diesel engine industry that convinced the engine manufacturers to allow the Jake Brake to be installed on their engines without voiding the warranty. Way to go, Clessie ! ! !

Dr. Lee :cool:

[TurboDiverArt]

Thank you both for the reply. Pretty cool stuff! I doubt I'll ever be towing anything remotely heavy enough to warrant putting one on. If the Jake Brake is what I think I'm hearing, they'll scare the hell out of you when next to one. Still a really cool sound!

Thanks,
Art.

[HowieE]

The "exhaust brake" that is used on our size trucks is mounted in the exhaust piping and when activated closes the exhaust pipe to produce high back pressure and thus impart some restriction on the flow of air through the engine. While not as effective as a true Jake Brake my exhaust brake will hold my truck, 16,540lbs, to 55 mph on a 6% grade without any peddal braking. Decellerations in traffic are greatly improved with the exhaust brake coming on as soon as I come off the throttle.
If you consider towing a larger trailer consider an exhaust brake and an upsized exhaust system right after the boost and EGT guages