Multi-Displacement System or cylinder deactivation

[Lonnie time to go]

Would this concept work on 8V71 just asking please be nice



Chrysler Group said it will offer the Multi-Displacement System (MDS) to its Ram trucks equipped with the HEMI engine. Currently the Chrysler 300C, Magnum R/T and HEMI-powered Jeep Grand Cherokee employ the cylinder deactivation system to help save fuel by 20 percent. Chrysler says MDS equipped vehicles sold in 2006 and 2007 will save 63 million gallons of gas.

http://en.wikipedia.org/wiki/Variable_displacement

http://www.leftlanenews.com/2009-dodge-ram-with-hemi-v8-could-top-segment-in-fuel-economy.html


Lonnie

[Zeroclearance]

It won't work..  No spark plugs in the 8V71..

[Lonnie time to go]

LOL  Can you shut down cylinders with a switch

[RJ]

Lonnie -

On an MUI engine like you've got in your 4905, you'd have to come up with some way to disable each of the mechanical injectors.

On a DDEC engine, the injectors are controlled electronically, so theoretically the "black box" could be programmed for this type of operation.

Would it work?

Who knows - but it might be an interesting experiment for those who are programming whizzes and can crack the DDEC code.

FWIW & HTH. . .

[bigjohnkub]

Many years ago, 1971 to be exact , The USAF provided our group with a new Little Giant 20 ton truck mounted crane. It had an International diesel engine in the truck carrier. Threre was a cable to pull out when roading to run on 4 of the eight cylinders. It worked somewhat, but I never used much. An 8 wheel drive truck with a crane on it's back need all eight all the time. Never seen another one. I guess no one else liked it either. Besides, diesel was free from the USAF. If I remember correctly, it was called a "swirl Destroyed " engine.
  Big john

[Lonnie time to go]

Thank you guys curiosity got the best of me

This would be good if on the highway you could shut down a couple cylinder



Lonnie

[kyle4501]

Never mind, bevans6 said it better than I did 

[bevans6]

with everything else equal (which is obviously never the case) cruising at a given speed  requires a given amount of horsepower, which requires a given amount of fuel.  The reason MDS works in a Chrysler Hemi is that the engine is so powerful that when it is throttled back to produce only the small amount of power required to cruise a pickup truck at highway speeds, it's very inefficient.  Turning off 4 cylinders and making the remaining four cylinders operate in a more efficient mode results in greater economy.  A gas engine is most efficient operating at full throttle, with power balanced against load perfectly.  A diesel engine doesn't have a throttle, power is balanced against load by the amount of fuel injected.

Also consider that the Hemi has a fair bit more power than a 8V-71, roughly 350 hp vs 270 hp (in typical bus tune).  Yet it is carrying a vehicle that weighs around 20% of what the bus weighs.  Bottom line is the bus with the 8V-71 is already balancing power against load pretty effectively, and taking a few cylinders away wouldn't make a material difference to economy.  A MC-5 with a 6V-71 isn't more economical than a MC-5 with a 8V-71, when both are driven identically, I would bet.  A bus cruising at 60 mph with a 8V71 is probably using around 50% of the available power.  A pickup cruising at 60 mph is probably using 10% or less of the available power of the Hemi.

If you were to hack the DDEC code, you'd also have to get the exhaust valves to stay open or the pumping loss of compression against a dead cylinder (sound like what happens with a jake brake on?) would negate any potential gain.  I'm not sure you can do that (keep the exhaust valves open all the time) with a DD.  On the Hemi, they keep both the intake and exhaust valve closed all the time, to kill the cylinder and somewhat balance out the pumping loss.  Keeping valves closed is an easier trick than keeping them open...you could, for one thing, just collapse the lifter.  I have no idea how they actually do it.

Brian

[Don4107]

I suppose on a mechanical V engine one rack could be selectively disengaged given enough thought and design time.  Don't have any idea what would happen.  i would be concerned that you might create some bad harmonics in the crank.

What are the firing orders for the common Detroit V engines?

In the 70s I played with plugging one primary barrel on a 350 Chevy.  Effectively cut off half the cylinders because of the dual plane manifold.  It was a four barrel so when you got on it the secondaries would feed the cut off cylinders.  Ran, but was gutless and pretty rough.  The cut off cylinders sucked oil past the rings and fouled plugs.  Did not run if far enough to find out what it did for mileage.   

[Ed Hackenbruch]

Don't i remember back in the 70's or early 80's that Cadillac and maybe somebody else had a car that could switch off some of the cylinders? Seems to me that it did not pan out at the time.

[baker4106]

Chey has a v8 that does that but its a gas engine.   In the 70's International Harvester put a V8 (550?) diesel in a tractor and it ran on 4 cylinders until the governor kicked in the other four.   Engine wasn't any stronger or better fuel consumption than their 6 cylinders so they discontinued production.   It was a nice sounding engine though.

[Busted Knuckle]

OK Say you do find a way to "disable" the injectors in some cylinders. Where are these cylinders going to get something to "lubricate" them while "disabled"?

In a 2 stroke diesel is more than most people think it is! Not only does it burn, but it also lubrcates the cylinder walls too!
FWIW
  BK 

[Lonnie time to go]

Thank you for the info guys

Like I said curiosity got to me after seeing commercials on TV


Lonnie

[TomC]

MTU (Motor Turbine Union) the industrial engine side of Detroit Diesel, has that feature on the 4000 series.  Hear in Los Angeles, the Catalina Island Expresses uses twin MTU 16V4000 (3,200hp each) through jet drives.  Below 1200rpm (I think) they run on 8cylinders.  Then above 1200rpm all 16 kick in.  Really saves fuel when idling and running at harbor speeds (5 knots). But-they are electronic, and have an exhaust valve lift to eliminate compression on those cylinders also.

I think you're going to find that the 8V-71 is just not that big of a power house and you're going to want all 8 cylinders all the time.  Good Luck, TomC