What's a jake brake?

[CraigM]

What\'s a jake brake?

The other day, I was driving home on Rt 81 just north of Harrisburg. This road is very heavily populated by the big trucks. One coasted up along side me on a long gradual downgrade and decided to trim a few MPH with the jake brake. I'd heard this plenty of times before from a distance, but when it happens right next to you, you can feel your teeth rattle. Does anyone know what in the world they do to an engine to cause such a God-awful racket?



Craig
Hershey, PA

 

[Bird]

Re: What\'s a jake brake?

/w3tcompact/icons/laugh.gif/w3tcompact/icons/laugh.gifCraig, I'm not enough of a mechanic to accurately describe the "Jake" brake (slang for Jacobs, I believe), but there are number of "exhaust brake" configurations. But the way the Jake brake has been described to me is that it changes the timing on the opening of the exhaust valves so they don't open to let the exhaust out immediately when the piston starts back up, but instead build compressed exhaust gasses in the cylinder, then when the exhaust valve does open, it sounds like a little explosion when those gasses are released. Anyone want to try for a better description? I guess a lot of people don't like the sound, and the last time I went to Alaska, it seemed like every little town we went through in Canada had a sign at the edge of town telling truckers that the use of engine brakes was prohibited in that town.

Craig, after I tried my half baked description, I happened to think that you could probably find a much better one on the Internet, so try this link http://www.jakebrake.com/products/engine/theory.htm

Bird<P ID="edit"><FONT SIZE=-1>Edited by Bird on 11/6/00 12:13 PM.</FONT></P>

 

[CraigM]

Re: What\'s a jake brake?

Bird:

Thanks for the link. Your description was really pretty close to the mark. I am constantly amazed by the amount of stuff out there on the web. Just didn't occur to me to look
it up there.



Craig
Hershey, PA

 

[bpence]

Re: What\'s a jake brake?

This may sound kind of silly, but I think I now have the topic for lunch discussion tomorrow. Thanks, guys. Jake Brakes. Who'd have thought. I've never heard of these before.

Bob Pence

 

[Anonymous Poster]

Re: What\'s a jake brake?

Yup, nailed the Jake brake, origin of name and how it works. The yuppie larva trucker wanabe calls his exhaust brake by Jacobs, BD, DeCelerator, or whatever a jake brake but it I S N ' T because it doesn't change the engine timing just closes off a fair percentage of the exhaust passage, albeit with a lot less noise than the big rig's jake brake.