Variable Displacement

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Sep 7, 2005 | 12:48 PM

justing

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Variable Displacement

Alright this may be a horrible idea but here goes anyway:
A new features on upcoming cars is Variable Displacement Engines. For example the Chrysler 300C has a V8 Hemi that can become a 4 cylinder. I’ve spent some time researching this technology and it seems that when you get right down to it they are simply cutting the fuel to half of the cylinders.

Now with that said what would be the feasibility of rigging up a button in the cabin of my expedition that I can press to cut the power to 2 or 4 of my fuel injectors while I’m cruising on the highway? In essence wouldn’t it simply push air in out of those cylinders?

I know there would be a problem of uneven wear on the engine but what other problems would you see coming from something like this?

Sep 7, 2005 | 01:23 PM

scholzee

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From: Grand Island, NY

First I would think there would be more "clean air" in the exhaust system from the unused cylinders, I believe this would fool the O2 sensors into thinking the motor was running lean and adjust for more fuel. The computer may detect misfires from the cylinders without fuel, I believe some of the new systems can chanege the fuel, spark and valves to accomplish this and the computer is aware and can adjust. In a nutshell I thing the computer would have the biggest fit with your method.

Sep 8, 2005 | 01:19 AM

Monsta

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From: Washington State

There is a guy in the V10 forum who is "experimenting" with it. Rather than unhooking injectors he is fooling the computer into going into "limp home mode" where the cylinders will alterante as if the engine is overheating.

So far, it is working but long term effects are unknown.

The advantage of the MDS system is that it closes off the cylinder and trap the air inside to acts as a air spring. This reduces pumping losses, or rather, minimizes it over just cutting fuel.

I feel it is it were as easy as unhooking or depowering injectors then a system would already be in place.

Last edited by Monsta; Sep 13, 2005 at 04:30 PM.

Sep 8, 2005 | 11:04 AM

justing

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Thanks i checked the posts there. It seems like he's a few steps ahead. I appreciate being pointed in the right direction.

Sep 8, 2005 | 12:04 PM

oldfordtrucksrule

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Joined: Dec 2002

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From: Effingham,IL USA

the hemi engine has special lifters that stop moving the valves when in the "4 cylinder mode" goin down the highway.so not only does the fuel injector shut down, but the valves stop moving, so you have half the displacement that u did b4.

Sep 13, 2005 | 03:41 PM

Iceman8984

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Joined: Oct 2003

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From: North Carolina

I don't know about this variable displacement thing, GM tried it back in the 80's on some Caddys. I know with todays technology it should be a whole lot better but I still have nightmares about the one my Dad owned. Ended up putting an olds engine or some thing in there................ God help the poor mechanics!

Sep 13, 2005 | 04:33 PM

Monsta

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From: Washington State

GM's design pre-dated even the Internet. Look how far technology (especially automotive) has come.

I can understand your concern but that is like saying "I wouldn't own an Apple G5 computer because my old Apple II didn't work very well."