Corvettelvr73

In class today a friend and I thought about how he could get better gas mileage in his 5.9L Durango on the way to the mountains today (3hr trip). If you were to disconnect every other fuel injector and that supporting sparkplug wire according to the firing order would this be safe. Then reconnect them when you are off the highway? Do you think this would be a huge difference? He averages 11.7 mpg now. :grouphug: :smiliedrool:

Larry B.

I know it sound like it would work... but.... A non firing cylinder or cylinders actuall decreases fuel economy. You would need to keep the valvs open too.. There have been a few designs that actually elininated some sylinders under certain conditions and none of them worked very well.

PRNDL

do a little research on "displacement on demand" - enjoy the economy of a 4 cylinder while puttering around, and the power of a V8 when you need it! :lol: GM supposedly has advanced the technology and will use it again in the near future. Might have tested it with that 1000 hp concept cadillac ? Was that a 16 cylinder engine?

SteveG75

NO. NO. NO.

Injectors would still inject fuel. So, you would just be pumping raw gas out the engine. Acceleration would require more throttle since you would only have half the cylinders firing. BUT, the non-firing cylinders would still get gas. I would actually expect mileage to DECREASE.

Just tell your friend not to floor it all the time and use cruise on the highway to hold a steady speed. My Avalanche gets 12 around town and 18+ on the highway. It is the acceleration that kills your mileage.

Cookwithvette

Chrysler is using a DoD system in their new "300" and GM will be putting it's system into production in 2005.
http://www.chrysler.com/300/features...ndex&type=left

The engine MUST be designed for such a function. Disconnecting plugs and injectors is a very bad idea. Your best bet for increasing fuel economy is driving steady, removing as much weight as possible before the trip, and being sure your tires are properly inflated.

As of now I've read of DoD functionality in Chrysler's HEMI V8 and on the Chevy side a V6 and a V8.

This tech was tried many years ago and it sucked hard. However... that was before computer controls. I think they can do it now. :cheers:


[Modified by Cookwithvette, 1:18 PM 5/7/2004]

7t5

THE Displacement on Demand system on GM vehicles is right around the corner--I think next year. I work at the engine plant where the LS1 truck derivitave motors are built and the process is almost ready to go. The reason it works is the cylinders will be activated and deactivitated seamlessly and automatically. If done to a motor not designed for this, as earlier mentioned, you would have a significant loss of power for towing, initial takeoff, passing, etc. The D.O.D. only works in low stress low power times like cruising on the freeway at 55mph, for example. The D.O.D is going to be great and I can't wait to drive one.

Fevre

I take it they are designed to 'drop' cyl similar to rev limiters that drop cyl in rotating order so it is not the same cyl dropped each revolution? Seems that would make the most sense and be best for the eng.

7t5

Actually, no. It drops cylinders evenly on both banks so the vibration isn't obnoxious. I also am under the understanding that the cylinders drop off immediately after the intake stroke so the air is constantly compressed and decompressed, acting like a spring and helping to lessen parasitic losses. When cylinders drop, the valves stay closed, fuel is shut off and spark stops until there is a need for more power . At this point the valves and fuel and spark become operational in those cylinders. The engine is then operating on all cylinders until lower power levels are required at which point the cylinders drop off again. it is quite a complicated thing but much more advanced than the V8-6-4 that was very embarassing for the General so many years ago.
Sorry if my explanation is unclear. If you don't get it ask again and I'll try again.

vetteboy1976kr

How do they keep the valves closed? I'm assuming that it is either a pushrod or OHC engine, so either way the cam operates the valves in normal operation, right?

RMVette

This is the same concept that was out in the early 80's with GM's 8-6-4 engine. Didn't catch on. :seeya

Schmucker

I think with electronically actuated valves it would be very possible, and they would make system that go right on our old engines, but those are a few years further. You actually wouldn't have better fuel economy by just flatout disabling pistons, assuming you didn't have to fight compression or anything. It would still require the same horsepower to move the engine along and the volumetric efficiency (VE) would be unchanged. With a good displacement on demand setup the VE is increased with the other cylinders being shut off. Twice as much air is available for the pistons to use at a given throttle opening. This results in an increase in port velocity therefore an increase in VE. So it is more efficient at making the necessary horsepower to move the vehicle.

wcsinx

A VTEC like system could do it.

Z-man

Didn't I read an article stating that the new Vette will soon have a DOD option? The computer shuts down 4 injectors and electronic actuators on the pushrods expand to keep both valves on the non-operable cylinders open. (If they are closed, you have pumping/compression forces to overcome).

:)

Robert N

Had a 81 Caddy with the system. If memory serves, the system would automatically adjust from using 4 to 6 to 8 cyclinders based on demand. In town driving had the engine "hunting" and never really saved gas. I would have prefered a system that allowed me to choose the # of cylinders used. Select 4 for highway cruising, 8 when needing to merge, then drop back to 4 kinda thing.

7t5

I think it allows the lifters to collapse so they cannot lift the valve.

Avette4me

bwahahahaha..retardedmofo... :blueangel:

BSeery

Difference ?? hell ya he'll get a difference. Try a "Check engine" light that will show up immediately, and that's if it even starts up. Next will be horrible vibration, no power and even worse gas mileage if it manages to move.

Tell him if he wants gas mileage in a truck, to ditch the 5.9 and get the 3.9 or 4.7.

and :rofl: :rofl: to him for thinking he would EVER get good gas mileage in a V8 truck !

mrvette

The DOD system can work quite well according to what I have read, and it makes perfect sense....accept for dragging a piston up and down against ring friction, and physics of course....

but it requires electronicall activated valves, and then the rest is easy....

but without that solenoid/electronic valves, the issues are allmost insurmountable....hense the 4-6-8 option caddys that didn t make it....

GENE

Cookwithvette

:iagree: BINGO! We have a winner!

http://www.canadiandriver.com/articles/jk/020710.htm

battsup

I work at a chrysler dealership and i talked to a couple of mechanics about this new system on the hemi and they said that even if it does end up working it wont be worth the money in the long run because of the all the differents things that can break.