I am having a debat with someone about the reasons why engine brakes arent available on diesels smaller than semi's. Is it cost or is there a mechanical reason. I understand fairly well how an engine brake works but I dont really know if it puts any stress on the engine in anyway. I read before that a light/medium diesel couldn't take the pressure of an engine brake. Also this person says that an engine brake would work on a gas engine. I cant seem to argue anymore so some other input from someone else would be great.

 

an engine brake doesn't make pressure... it releases pressure...

the problem is that our little motors don't have cam triggered injectors, so there's no easy way to time the opening of the exhaust valves when the piston is at/near TDC

Forrest

 

Its not that it would not work......it would,but on a isb one would have to reprogram the ecm to make sure fuel never got dumped in with the ex valves open.
And of course someone has to make a assy or unit that will hold the ex valve open to creat the jake effect.
the hole idea is the eng. being a airpump- hold the ex valve open /no risidual compression=more drag so the piston is not helped over center at all........
That help??

 

most jakes I've seen use the cam to actuate the valve opening... timed closely with the injection event. it would be a LOT of work to retrofit one to a B series...

sure wish there was an affordable Jake for the 12v though!!!

 

I guess I'm getting smarter ?? I didnt realise that there was a difference between a engine brake and an exhaust brake. Can someone elaborate a little on this??

 

an exhaust brake is just a butterfly in the exhaust... when closed, it creates a lot of backpressure that the engine must work against, thus slowing it down...

an engine brake is a fairly complex setup that opens the exhaust valves right around the time that the piston is at TDC.

on a diesel, you have no throttle body, so the engine takes in a full breath of air, that is then compressed, and then the compressed air pushes back on the piston... on a gasser, you don't have that compresson, and the engine slows quickly as it fights against the throttle body creating vacuum.

with an engine brake, that compressed air is released past the exhaust valves when the cylinder pressure is still quite high... there's no more pressure to push down on the piston, the engine slows, and the escaping pressure emits that beautiful sound we all know and love!!

whenever I'm coasting, I can hear exactly how my truck would sound w/ an engine brake, and it almost brings a tear to my eye to think how great it would sound!! LOL!

 

I know what you mean. I love that sound. But think about how funny you'd look with your face stuck to the windshield! An engine brake develops some serious braking force, roughly equal to the torque the engine is capable of at a given RPM. The exhaust brakes can only generate about half the braking force, and only at high RPM. Many engine brake setups have a selector switch for 2, 4, or 6 cylinder braking so the driver doesn't get shoved into the steering wheel every time he gets off the gas in an empty or lightly loaded truck. You can hear the difference when a truck is set for 2 or 4 cylinders, listen for a truck that "stutters" coming into a toll booth and you'll hear what I mean.

 

also the engine doesnt have to have a cam actuating injector , the ISL which is similar to the ISC and ISB has a Jake brake set up just like the big boys.

 

Actually an engine brake doesnt just let out the air around TDC. It opens the exhaust valve around half way down the power stroke releasing the pressure then closes the valve again while the piston is still traveling downward causing a vacumm. Which is what slows the engine. What I dont know is why have I read that the ISB (smaller diesels) cant take the abuse of an engine brake?

 

I am finding this very interesting!! I now have to smile, because of all the small towns I go through that specify "No Exhaust Braking Allowed", when I think they want to say "No Engine Braking Allowed"! Am I right that the engine brake is the really loud one, not the exhaust brake? I can just see the look on the local prosecutor's face when the judge dismisses the case!

 

Yep, exhaust brakes are pretty quiet. Some trucks have both an engine brake and an exhaust brake, this provides even more braking power and also quiets the truck down some.

Anti-engine brake signs I've seen:

"Use of Jake Brakes Prohibited" -Does that mean a PacBrake is OK?

"No Retarding Devices To Be Used Within City Limits" - I guess that means no television in this town.

"No Engine Brakes Allowed" - Does this mean you have to stop and remove the engine brake before proceeding through the town?