Downshift or exhaust brake?

Grit dog wrote:

IdaD wrote:

4x4ord wrote:

Grit dog wrote:
While I’ll likely not tow heavy enough to make great use of a compression brake, the Load Leash is just another example of how awesome a time we’re living in for vehicles.
I mean having a pickup truck with exhaust brake and a real Jake brake? Pure awesomeness!

The LoadLeash sounds like a step up from an exhaust brake on its own but still quite a step down from a "real Jake brake" in my opinion. I wonder how long it will be till we see the energy used in braking stored as compressed air or in batteries to be used to climb the next hill.

I think the new light hybrid Ram (I forget what they call it) has regenerative braking.

Yet another cool means of slowing a vehicle sans service brakes.
4x4ord, how is a load leash a step down from a Jake? I'm no big diesel truck expert, but are they not both mechanical compression brakes?
On a side note, I wonder when we may see hydraulic retarders enter the heavy (light duty trucks) pickup market either engine or trans? Especially trans retarders. With today's bulletproof and computer controlled transmissions, I bet the components are almost all already in place for this.

The Load Leash requires an exhaust brake to reach its full potential. It holds the exhaust valve slightly open while engine braking. This means on the compression stroke the air is pushed past the slightly opened exhaust against the 60 psi or so pressure maintained by the exhaust brake. Because the exhaust valve is slightly opened and the exhaust brake is maintaining high back pressure the cylinder will fill with exhaust on the power stroke. This exhaust can be forced past the exhaust brake again on the the exhaust stroke. So for every two revolutions the engine is filling its cylinders with air twice. First revolution will be with intake air and second time with exhaust. Every time the piston comes up it is pushing against the pressure maintained by the exhaust brake. So the Load Leash would have nearly double the braking effect that a normal exhaust brake would have.

With a "Jake Brake" (or decompression brake) the piston rises up on the
compression stroke building very high cylinder pressure with both valves fully seated. (I'm going to guess the cylinder pressure might rise to 800 psi when the turbo is creating 40 lbs boost during engine braking on our Cat C15). When the piston approaches top dead center the exhaust valve is popped open letting that very highly compressed air escape out the exhaust valve so that it isn't able to expand against the piston on the power stroke. So with a "real Jake brake" the engine only fills once with air per two crank revolutions but there is a tremendous amount of braking accomplished on the compression stroke.