The Stovebolt Site Forums The Shop Area General Truck Talk V4-6-8 engine reborn?

Years ago I saw a Caddy with weird looking valve covers, and on the side it said V4 6 8.

The owner explained it was some (at the time) new fangled method of increasing fuel economy.. the engine would run as a V4 for around town driving, as a V6 when you needed a little more power, and as a V8 when you really put your foot into it.

Most people i've talked to about it said the engine wasn't used but in just a few model years, and the idea was eventually scrapped due to numerous reliability issues.

Flash forward to present day.. on a commercial for the new Chevy Impala, I saw that a simular idea was being used in the SS models, now called "DOD" or Displacement On Demand technology.

From the chevy website:
A 303-hp small block V8 is standard in SS and features Displacement on Demand (DOD) technology that uses eight cylinders when you want more power, four cylinders when you need better mileage — delivering an EPA estimated, petrol-pinching 28 MPG highway.

What do you think?

fumblin - i am not sure what i think about it but the nee "hemi" in the chrysler cars has this same technology which, so they claim, gives the new charger almost 30mpg on the highway. it is not a new technology, it was scrapped on the old caddies cause the idea was ahead of the technology of the day and too many problems occured. i think that technology is probably good enough now to make this idea work. i like the idea in some ways but i am not sure that i want my car deciding for me when it is going to do. same reason that i am not big on throttle by wire, or active stability controllers, maybe i am just old fashioned, who knows. neat technology though.

I have driven the Chrysler 300C hemi on a long trip and it really works well. I couldn't detect any change in the engine operation and it has more than enough power for me. In addition,it got better mileage than a Chrysler mini van. However, the car is not something that I would buy, even if I had the means! The styling causes problems with the view down the side and to the rear. It is also a rather large sedan.

The Caddy engine was used in the 1980 model year only, as I remember, and had a moveable valve rocker arm pivot that disabled the intake on several cylinders as it cut back to 6, then 4 cylinders in operation. It would drop back to 4 cylinders very nicely, but it was reluctant to come back to full power quickly. Cadillac was replacing engines regardless of mileage a couple of years later at no charge, because the perfromance was so lousy. Maybe Chrysler's got it figured out now, but I'm not holding my breath until it happens!
Jerry

I drove a HEMI 300C recently and was quite impressed! The change from 8 to 4 was imperceptible, as was when you hit the gas, the eight came right back and allowed for smooth, speedy passing. My niece has one she uses in her real estate job, putting as much as 300 miles/day on it at times. She has 45K on it now, and says it has been trouble-free.

The old Northstar 4-6-8 relied on mechanical drive to cut out the cylinders. Northstar recently went with electronic control called variable valve technology, and now have a good engine. I was reading Car & Driver last night, said that Chevy was going to use the engine in the new Tahoe/Burb they are coming out with.

The 4-6-8 is ABSOLUTELY NOT A NORTHSTAR.

The caddy northstar was introduced as an alternative to the 4.9L motor in the '93 model year for most FWD cadillac autos, and it displaced 4.6 liters (289 CI). The 4-6-8, by comparison, was introduced in the '80 model year, and displaced over 300 cubes. Additionally, the first generation of northstars (93-95, prior to OBD-II implimentation) did not have DoD, and the northstar VVT wasn't available until after 2000, and only on the Cadillac mini-suv (at least it was facing the right direction, all previous northstars were transverse mounted)

Pontiac developed a car called the "GXTP" which had a northstar under the hood, not sure if it ever went into production but I sort of doubt it.

I have a 2005 Dodge Magnum R/T with the new 5.7 Multidisplacement HEMI and I love it! Like previously stated you don't really notice the engine dropping back to 4 cylinders when you are cruising down the highway and there is no hesitation when you jump on the gas and the engine goes into 8 cylinder mode. I don't really baby the magnum as I drive it to and from work mostly on highways traveling at 65mph and I have been getting 20-21mpg, they claim you can get up to 25mpg highway, but I have not seen it yet.