Multi displacement engines

[fredjacksonsan]

I've recently read a (very) short article on multi displacement engines. The gist of the article was that there is some sort of oil interrupt that would keep the valves from opening.

Does anyone have some info on these systems and how they work (or a link), and reliability info?

Thanks in advance.

[curtis73]

You can maybe try www.howstuffworks.com . Sometimes they have stuff like this.

I know that some of the diesel manufacturers are experimenting with hydraulically operated valves and one of their objectives is multi-displacement and variable dynamic compression. The "cam" is very much like the fuel pump in a diesel; computer controlled high pressure, but it presses oil into a lifter cavity. The computer controls how and when it sends oil to the lifters thereby creating nearly infinitely adjustable valve lift and timing.

That's the only system I know of right now. I'm sure I read about another one somewhere but its escaping me now.

[MagicRat]

Cadillac had a multi displacement engine back in 1981. It had a solinoid which would close 2 or 4 intake valves under light throttle operation to save fuel. The called it the V 8-6-4. I have one in a parts car. According to the original owner, it worked flawlessly for the life of the car. However, it suffered from a bit of hesitation as it cycled from 4 to 8 cylinders.

I believe the current Chrysler Hemi as a similar but much more sophisticated system.

[curtis73]

I think the original owner got lucky. They were not reliable by any stretch of the imagination. I was joking with a guy once who said that he was going to take out his 8-6-4 and put an Olds 350 diesel in its place to double its reliability.

[MagicRat]

Originally Posted by curtis73

I think the original owner got lucky. They were not reliable by any stretch of the imagination. I was joking with a guy once who said that he was going to take out his 8-6-4 and put an Olds 350 diesel in its place to double its reliability.

haha
These things did have a bad reputation and resulted in lots of warranty claims, hence they were a one year only option.

I actually had two of these jewels.
The other one had an electronic glitch which made it run on all 8 cylinders all the time. As this was an improvement, I suspect it was not a glitch at all, but was a deliberate modification on the part of the previous owner.

I pulled that engine out and installed an olds 455.