8-6-4 questions

I have a 1981 Coupe DeVille, it has the 368 with V864. I had it disconnected cause it sounds funny in 6 and 4 cylinder mode with my exaust and other reasons. But gas prices are up again and I'm tring to get better gas milage out of it. I want to put it on a switch so I can turn it on when I'm on the highway and off when in town. Will this work okay, has anyone tried it?

Hey Coupe:  I have the 1981 Fleetwood Brougham with this engine configuration and I have the electrical manual for this year. After going over the specs. my recommendation to you is to not tamper with the system. We are talking about buffer amplifiers, computer command control, vehicle speed sensor circuits, unless you are an electronic wizzkid then you will be opening a can of worms trying to put a switch somewhere in the right circuit. You will undoubtedly end up in a world of grief for just trying to save a buck on gas. This is quite a complicated system which also has many subsystems that all work together.The ECM controls the cylinder selection through the MODULATED DISPLACEMENT DRIVER AMPLIFIER . When five conditions are met then the ECM program will select the 6 cyl. mode, when another three conditions are met then the four cyl. mode will take over. All of your circuitry will have to be in near perfect working order for all this to happen flawlessly. Mine does not function at this time and I don't intend to worry about it at all. The problem with this engine too is that there are no mods that I know of to help  out in the mpg area. Hope this helps there dude.

Ii totally forgot these things were made.
Does any one know how are the new Dodge Chargers alike these 8-6-4 engines?

This is a write up on the modern Hemi.
Does anyone have a write up on the Cadillac engine?
 

quote:

by Allpar
The 2005 Chrysler 300C and Dodge Magnum RT were the first high-volume, modern production vehicles in North America to feature fully-functioning cylinder deactivation; at Chrysler, they were followed by the 2006 Durango (Honda came out with a cylinder-deactivating V6 later). The MDS (“multiple displacement system”) seamlessly alternates between fuel economy in four-cylinder mode, and power in V-8 mode. Owners receive the powerful benefit of the Hemi engine with the fuel economy that they would expect from a less powerful V6 engine. Most test drivers cannot tell the difference.
"The MDS was part of the engine's original design," said Bob Lee, Vice President Powertrain Product Team, Chrysler Group. "This resulted in a cylinder-deactivation system that is elegantly simple and completely integrated into the engine design. The benefits are fewer parts, maximum reliability and lower cost."
This system should triumph where the Cadillac 4-6-8 failed because of the speed of modern electronic controls, the sophistication of the algorithms controlling the systems, and the use of electronic throttle control. The HEMI will be able to transition from eight cylinders to four in 40 milliseconds (0.04 seconds).
The system deactivates the valve lifters. This keeps the valves in four cylinders closed, and there is no combustion. In addition to stopping combustion, energy is not lost by pumping air through these cylinders.
Fuel economy gains go up to 20 percent under various driving conditions, with a 10 percent (or so) aggregate improvement, without any change in customer experience—drivers will receive the benefit without changing their driving habits or losing power.
Don Sherman's article in Automobile noted described a test of the MDS. They found that only four cylinders were used during 17% of the suburban traffic portion of the test, during a full 48% of the freeway test which included "over 70 mph" speeds.

Overall, they found that the engine powered down to four cylinders about 40% of the time. Non-enthusiast drivers may experience even more savings. As with most testers (including us), Don was generally unable to detect the changes from four to eight cylinders and back again.

Chrysler engineer Cole wrote: "The modern HEMI always shuts off the same four cylinders. In our duarability test cycle (150,000 customer equivelant miles driven at the 95 percentile, meaning that only 5 percent of our owners are more abusive than our testing), we have not found any adverse wear patterns." (Chrysler PR materials boasted of “over 6.5 million customer-equivalent miles through development and durability testing.”)

for more, look here:

http://www.allpar.com/mopar/new-mopar-hemi.html

You don't think I can run a switch off of the sensor you unplug from the transmisson to dissconnect the 864? I want to switch it cause I don't like the way it acts in town, but need the mpg.
 
Oh and the new Chevy's and Dodges with variable displacement, they only switch from 4 to 8, no 6. There's a odd vibration in 6 mode.

If you keep your foot in it a little , you can keep in 8 cyl mode. In 6 cyl. mode at low engine speeds they all shake, its just physics,and the 368 is a paint shaker. Fortunately they normally don't stay in 6 cyl mode much. The ones I drove a while back weren't too bad in 4cyl. I would leave it alone as long as it working right and learn to drive it so it does what you want it to do.