LMM Air Intake Valve - Jake?

[moondoggie]

Good Day!

Per a new DP article, the latest LMM DMax has an Air Intake Valve that was added to the intake plenum, just upstream of the intake air heater. Wouldn't it be possible to program it to close (variably too, I'm sure) to increase engine braking?

In the good old days, we used to call engine braking "compression braking." When I got my 1st diesel (below), I wondered: if it's compression braking, why then does this 21.3:1 CR engine cause my truck to feel like it's falling off a cliff when I go down a hill almost regardless of gear, while ANY gas engine car/truck (9:1 CR or so) can gear down to hold the hill?

I figured it out. The gasser is actually a vacuum pump - that's what makes it hold the hill better than a diesel. The gasser has a throttle plate, the diesel has none & takes all the air it can all the time.

I can't wait to hear your thoughts. ;)

Blessings!

[JohnC]

Better still:

Program the vanes in the turbine section of the turbocharger to close and make it into a compressor. I thought I read that they actually do this in the heavier trucks.

[More Power]

Lots of vaccum on the intake side might suck more oil past the piston rings and the valve guides.

Jim

[Robyn]

The two bsic types of engine brakes are the exhaust flap that actually closes off the exhaust outlet and runs the engine up against back pressure.
The other type that is found on the big trucks is the Jake type.
The jake has an electrically operated hydraulic device that uses oil pressure to operate a mechanical divice that opens the exhaust valves just as the cylinder aproaches TDC on the compression stroke.

The fuel is shut off completely and the 600+ PSI cylinder pressure are dumped off rapidly.
The piston then has to be drawn down on a dead hole.
The engine effectively turns into a power absorbing air pump.

The fact that the high cylinder pressure is dumped off rapidly is the reason that jakes can be so noisy if the mufflers are not up to snuff.

The flap type brakes are relatively noise free as all they do is provide back pressure.

The diesel having no intake vacuum also negates its ability to offer any holding.

Under a no fuel condition the compressed air in the cylinder still imparts a lot of "Bounce effect" back to the piston on the down stroke.

Hope this answers your question

Robyn

[moondoggie]

Good Day!

"Lots of vaccum on the intake side might suck more oil past the piston rings and the valve guides." Never thought of that - I suppose for an engine (diesel) that is never expected to see a vacuum, the oil control rings might not be able to handle this.

"...on the big trucks is the Jake type. The jake has an electrically operated hydraulic device that uses oil pressure to operate a mechanical divice that opens the exhaust valves just as the cylinder aproaches TDC on the compression stroke." Cool! I always wondered how these worked.

"The fuel is shut off completely and the 600+ PSI cylinder pressure are dumped off rapidly. The piston then has to be drawn down on a dead hole. The engine effectively turns into a power absorbing air pump." I would write "air & vacuum pump." Wouldn't this create engine braking 2 ways? 1) Pressurizing the cylinder on the compression stroke (which is then vented, as you described); & 2) the vacuum created when the piston goes down on the (non-)power stroke? We know the vacuum situation works well from our gassers; adding the pressurization part of the cycle (#1 above) adds another apparently highly-effective engine brake. In fact, my guess would be the pressurizing part of the cycle is the more effective of the two.

"Under a no fuel condition the compressed air in the cylinder still imparts a lot of "Bounce effect" back to the piston on the down stroke." I guess that would be why taking my foot off the footfeed feels like falling off a cliff, at least when used to what happens in a gasser.

Thanks for another excellent tutorial, robyn! :D

Back to the subject: Any other reasons this wouldn't work? If the potential problems can be answered, maybe one of our top-notch vendors might find this worth working up, eh? ;)


Blessings!
(signature in previous post)

[Mountainman]

OK, you smart people (notice how I phrased that), why was it added to the
LMM?.....Emergency shutdown for runaway.....?

[diesel65]

Most likely it has to do with EGR issues.

[moondoggie]

Good Day!

"why was it added to the LMM?....." Read the article. ;)

[Mountainman]

Whoops! When DP was mentioned, I thought D Place not Page. I'll check it out.

[DmaxMaverick]

Whoops! When DP was mentioned, I thought D Place not Page. I'll check it out.

Find it HERE (http://www.thedieselpage.com/members/duramax/2007LMMEmissionsc.htm).

[Robyn]

Well I wont dissapoint anyone by saying how nice all this looks. :eek:

Sounds like enough electronics and goodies to power the Starship Enterprise.

I just shake my head at this technological nightmare.

What's all this stuff going to be like when the rigs get 200K on them and the goodies start falling off or stop working.

At least they are not burning down the local coffee hutch like the Ford flame throwers :rolleyes:

[Yukon6.2]

Hi
I got to see one of the new ford Flamers yesterday.I can see why you need to pull the cab to do any major work on the engin.And it dosn't take much to be major work.Everything is jambed in tight.I noticed the aftercooler pipes are necked down with lots of restricion to make it through all the wires hoses and miss stuff.The owner seemed to like it.
I wouldn't want to try changing anything,you would need a masterplan for wiring and hose placement.I wouldn't want to own it after warrenty ran out.Oh yea steared clear of the exhaust when i walked around:eek: