Dodge is going to offer Multivalve Displacement Systems in its Hemi engines in the new '06 Ram Pickup...in fact the entire Hemi engine line will have MDS, which shuts down valves when less power is needed increasing fuel economy.

Is this the future for V-8s? Isn't Ford supposedly working on something similar?

 

1) Sneak up behind a long-time Cadillac dealer and yell, "VEE-EIGHT-SIX-FOUR IN THE SHOP!!"

2) Call the paramedics and tell 'em to bring the paddles...

 

That Caddy system was absolute junk. One of the worst ideas in the history of internal combustion engines.

But now that we have sequential port fuel injection and ECU's that control hundreds of different engine parameters, things are totally different.

I do have reservations about the use of such a system in trucks, however, especially where heavy loads or towing is involved. A system that shut down cylinders under a "light load" situation, might not work so well with trucks carrying close to max payloads or pulling trailers close to maximum gross weight.

 

it's in the jeep hemi right now and seems to be working.

 

I never understood the theory behind this. You've still got all the internal friction you had before. Plus, the remaining working cylinders are now working harder. You decrease fuel vaporization by decreasing manifold vacuum. Yes, it's fuel injection, but manifold vacuum still has an effect. They should be focusing on something like variable valve timing, which WILL help. And I dont mean just advancing / retarding the cam with rpm, I'm talking about changing lift and duration with rpm and load. There are ways to do this. At low engine loads, reduce the duration and lift, close the intake valve earlier to build more compression, run it lean, and advance the timing. Duh.

Personally, I think the whole cylinder shutdown idea at low engine load is stupid. Note, I didn't say that about anyone on here. Just about the idea from the vehicle manufacturers. I am not calling anyone on here stupid.

 

They are still internal combustion engines. How can it be one the "worst ideas in the history of internal combustion engines." Yet add some electronics and now things are totally different??

It is a good idea but took modern day electronics to make it function better than the old Caddy system did.


Actually they are not. The air that is pulled inside the cylinder acts as an "air spring". The other cycinders do not have to use much of their power produced to "run" the deactivated ones. The deactivated cyclinders are just going along for the ride at that point. Not a whole lot of losses. Hence; fuel savings.



DUH? You make it sound as if the technology is available at the grocery store! If it is that easy it would be in effect now. Currently only F-1 car engines have that pneumatic valve technology. Do a search on camless valve actuation, too. Both are coming to production engines but not for a while.

Then don't buy a car/truck with it. It is a fuel savings idea and it works.

 

Actually, the technology has been available for years. That is what the Honda VTEC motors do. Not the camless thing, but the varyable valvetiming and varyable lift.

 

What is the tow rating on that vehicle? What I found says it fell from 7,700 lbs. to only 3,500 with the variable cylinder hemi engine. Is that right? I would not want that in a real truck.

 

While jeeps site isn't very clear, from what I've found, no. The hemi is the top in towing at 7k+ lbs. From what I understand it only activates under 2K RPM's and only at low constant throttle. Not gonna happen while towing anything substantial.

Anybody have a good site explaining the MDS?

Supposedly GM is coming with a near identical version soon.

 

If you think back, GM has had some real engineering blunders!! In addition to the Cadillac V-8-6-4, the 350 diesel conversion, the Vega all aluminum 4 cylinder, etc. .....

 

no flaming by me bob, but the vega was not that bad if run on lead free gas. i had one that had 100k before it wound up with a small block in it's place

 

The Vega's (and GM's) reputation with the aluminum engine was destroyed before unleaded gas was introduced. Briggs & Stratton was able to make aluminum blocks and leaded fuel work.

I think the 8-6-4 Cadillac failed because computers weren't developed enough to handle the task. I think the new technology will be more successful.

 

in the one i had was a 1971 and i ran amoco lead free all the time. they where the only company that had it back then

 

Mercedes 3.8L V-8 back then was all aluminum, and worked!!

 

You're right! I had forgotten about the "white gas". Where I live, there was only one station in town that sold it and it was very pricey. If you could afford to burn it, you could afford a real car.