'08 exhaust brake - how does it work?

[dutch6]

Is the factory exhaust brake on my '08 an engine brake (disables valves) or an exhaust brake? I had a Pac Brake in our old motorhome that sounded like sand in a coffee can. The brake in my '08 sounds like a Jake brake on a big tractor, only quieter. Don't get me wrong - I love the sound my truck makes when braking, just curious how it works.

 

[grasmo]

Yeah me too! I am not sure how the exhaust could withstand the pressure created by the load placed against it.

 

[AABEN]

YOU have an exhaust brake and a very good one. I thank you will like it. --BEN

 

[HBarlow]

It is actually none of the possibilities you offered in your question.



IIRC the turbo has a sliding nozzle which blocks exhaust discharge in the closed position. It works in almost exactly the same way as the previous Jacobs Exhaust Brake works only instead of a butterfly valve post turbo in the exhaust closing, the turbo itself blocks the exhaust discharge. The turbo has the capability for the nozzle to slide back and forth to give more boost at lower engine speeds and does not overboost at higher rpm so it doesn't require a waste gate. It can also close to provide exhaust braking.

 

[AStrand]

I just had one installed on my 07 with the 5. 9L. The factory ones on the 6. 7L must work different. My Jake is installed post turbo.

 

[jelag]

Harvey... . excellent choice of words.....

 

[grasmo]

I wonder how much pressure would be measured between the exhaust valves of the engine and the restriction device / sliding nozzle of the turbo during the activation of the turbo brake during an event?I've never really thought much about the theory involving an exhaust brake. It seems interesting though.

 

[HBarlow]

Harvey... . excellent choice of words.....

Thanks, Jim. Every once in awhile I stumble into posting something understandable.

 

[HBarlow]

I wonder how much pressure would be measured between the exhaust valves of the engine and the restriction device / sliding nozzle of the turbo during the activation of the turbo brake during an event?I've never really thought much about the theory involving an exhaust brake. It seems interesting though.

Not much. Several years ago when Jacobs Exhaust brakes were first offered for the earlier 12 valve engines it was necessary to change the exhaust valve springs to 60 psi springs IIRC so that the exhaust valve would not be held open by the back pressure created by the exhaust brake. Later engines had stronger valve springs and it was no longer necessary to upgrade them.