Can someone explain, technically, how the LMM and Ally engine braking works? Obviously there is no exhaust release mechanism (Jake) so how does this work exactly. I am assuming being a diesel since there is a nearly full return of compression energy, it must work by reducing intake manifold vacuum, thus simulating gasoline engine braking? I am also assuming that the braking I feel is not simply a lower gear being selected, because again if there is no compression braking the RPM's of the motor would be irrelevent.

Is it the variable vane geometry / design that makes Grade Working work; or something else? Any chance I have a Jake and all I need to do is blow out the baffles in the DPF, and the Muffler?? :D (Joking)

Thanks for the lesson, I'm just curious how this works.........

There is a throttle body on the LMM that could be closed to create pumping losses. Also I believe the vanes on the VGT turbo close to create exhaust backpressure.

I thought is was just a lower gear and used the compression of the engine to brake.

That's the nature of my question because there should be no compression (as an entire revolution, not single stroke) in a diesel once the fuel is shut down. But I know there is no true compression brake either, so just curious how it works...... There must be a mechanism for shutting down air intake in order to simulate a gasser, right? Or is there a mechanism on the exhaust side that I don't know about? Maybe both as mentioned above.

The butterfly valve ("throttle body" that has very little to do with throttle) is used to assist in increasing EGT's for regens. With stock programming the turbo vanes do not close to create additional back-pressure. Closing the vanes is done with EFI Live, Banks Speedbrake, or Fleece TurboBrake to create a software driven Turbo Brake that works extremely well. To the extent of my knowledge, in stock form Engine/Grade Braking is achieved by friction with no other contributing factors (increased exhaust pressure, reduced manifold pressure, etc).

Anyone confused by "no compression (as an entire revolution, not single stroke)", put a socket on your alternator pulley and turn clockwise. You'll see how easy it is to rotate the crankshaft. VERY LITTLE compression resistance, just resistance from friction.

I'll have to try that, I assumed that there was MASSIVE resistance on the upstroke, but that there is almost equally massive spring rate on the down stroke -- thus equating to zero resistance over the whole revolution cycle. Why would you be able to turn the engine over so easily, you still have, what, 10:1 or so?

NEVER MIND, I'm a moron............obviously the trapped compression in the other 4 cylinders are acting as counter-balancing 'springs' to assist in rotation of the engine. Course a gas engine would do the same thing I assume. My head hurts,.....

That is on thing that I'm a little foggy on. I had a 400 SBC, 9.5:1 CR, that was a PITA to turn over by hand. I had loaned out my trusty flywheel wrench and had to adjust the valve lash, turning the flywheel the hard way. The only thing that I can think of that makes a gas harder to turn than a dmax is camshaft profile. I don't know anything about a diesel cam profile, but if I'm thinking correctly a gas engine cam with a decent amount of overlap would release the "counter balance" pressure making it a one sided fight against the compression stoke.