BIG_MODS

iTrader: (9)

GM is incorporating DOD in there trucks soon. They also used it in the Cadillac 16 for the Detroit auto show so that it could go from 16-8-4 cylinders for better fuel economy. Is this as simple as shutting down the fuel injectors? Could this be rigged in a thirdgen TPI? Would it work? If cylinders on the right bank were shut down their lack of fuel wouldn’t affect the O2 sensor since it is on the driver’s side.

Just a thought. I was thinking of un-hooking an injector or 2 or 4 to see if it works.

Austin

Grumpy

This isn't anything new for GM, they tried it years ago, and it was a miserable failure. They do have a routine in the late Caddies where they shut down various cylinders when overheating to pump air thru the engine to cool it down when overheated.


Unplugging an injector will kill some HP, but that cylinder then costs energy to crank past TDC.

BIG_MODS

iTrader: (9)

yes, the dead cylinders will cause a loss due to friction power (sliding friction and pumping losses etc), but these losses will always be there even if the cylinders are firing. By shutting cylinders down, the cylinders that are firing have to make more power to account for the friction power from the dead cylinders and to get the same power output to push the car down the road. This causes a higher MAP, and engines typically have a higher fuel conversion efficiency (~power/fuel) at higher maps. Thats why smaller engines are typically more fuel efficient.

Can anyone think of a reason why this wouldn't work on a 3rdgen TPI? I did hear of Cadillac trying this in the 80's. Why did GM have so much trouble? Is the problem not with the concept but maybe controling it? I was thinking of wiring in some switches to manually shut down cylinders.

JPrevost

This isn't like the "shut down a cylinder to save gas."
It's more complicated.
http://www.reviewsonline.com/auto/gmdod.htm
Do a search on www.google.com and you'll find a LOT of information regarding the technology.
It's a good to see the v8 still selling. Now if only they could do phnematic individual valve control.... just think of the displacement on demand. You could activate cylinders in a specific sequence resulting in a very smooth operation. Even smoother would be the ability to keep the valves open under the compression stroke so as not to drag down the motors balance.
Next we'll see roller bearing cam shafts and hopefully gate or ball valves instead of poppet valves.
So anyways, nope, unplugging a cylinders injector will just make the car run like crap but if you're interested in doing it go for it.

Grumpy

Part of the selling point for the 42V auto electrical systems of the future is being then able to control valve movement, with solenoids. IH and others already have systems using it.

JPrevost

Yeah, but hopefully the general does it better than the rest and makes it backwards compatible .