Putting a switch on the passenger side fuel injectors fuse. I know that Mercedes-Benz did something like this once before with their "Displacement On Demand" V12. I could put it on a switch in my console, with my other switches, and use half the gas on the highway. I've pulled the fuse when I was tracking down a short and know it will run ok w/o those 4 cylinders.

So, do you think it's a good or bad idea?

 

I think mercedes put alot more thought into it then just rigging a switch to the injectors on the right side of the engine. Needless to say the computer will throw codes and the engine probably will stall. Thats just my personal thoughts of what would happen. Try it and find out!


Matt

 

I have pulled injector connectors with getting no codes or stalling, but that was only 2 at a time. I wonder if you are the first to think of this or someone else has and it was already deemed a bad idea.

 

Your right, Mercedes did engineer it out so that when the driver wanted to accelerate, the hydralic (sp?) valve train and the injectors come to life. A marvel of modern engineering. Of course the spark plugs still fired. But, theoretically, there should be no problems, other than a lack of power, but only when cruising. The O2 sensor is on the driver side manifold in my car, so that's why it would have to be on the passenger side.

 

Ever since Cadillac's 4-6-8 mishap in '81, I've been leary about cars that only run a couple cylinders at a time.

 

I wasn't around back then. Tell me about it.

 

I wasn't either, but Caddy rigged up a clutch system within the crankshaft valley where under 1/3 throttle, 4 cylinders were fired, with 2/3 throttle, 6 cylinders were fired and full throttle all 8 fired up. It was toted as an engineering marvel, but it ended up being an engineering mishap when the clutch systems failed. All engines were warrantied before the end of the model year.

 

WOW! That sucks! But, what I'm talking about doing is controlling the injectors with a switch. It's not like the injectors dont already take a lot of abuse. All I'll be doing is giving them a break.

 

caddy disengaged the valves for those cylinders, there were no clutches

 

How were they disengaged then? I've talked to owners of these car who know the history and they've told me that (upon different occasions) that there was a serious of clutches that engaged/disengaged the cylinders. The clutches were the part of the system that failed. If there were no clutches, I'd like to know how Caddy did disengage/engage the cylinders.

 

Ad far as i know there was some sort of solonoid that disconnected the valves. If you look at one there is some device in the valve cover thet is controlled by wires. i believe on the center 4 cylinders

 

I've seen on Car&Driver TV where GM is going to be doing that to the pick-ups/SUVs for the 2003 or maybe the 2004 model year. Can't remember exactly.

The ECM is in control of the entire operation though. It only works at speeds above 55 MPH and like 1/4 or mabe 1/3 throttle after constant speed has been maintained for a certain length of time.

Jim Schoutten (Spelling) test drove it and he said there is no change in the ride at all, and he could not tell when the system was operating other than a light on the dash.

IIRC, it's a random fire system also. It doesn't just cancel out #1-4-6-7 or #8-3-5-2 cylinders either (I know that's not the new firing order, but you get what I'm saying ). It probably has some other sequence it uses such as every 360* of crank rotation, and since each cylinder has it's own coil now, those may not fire at the same time the injector doesn't spray. Not sure.

I'm sure that GM's done it's homework on this one since that Cadillac system sucked so bad. Although they are still having trouble with the variable timing exhaust cam on the new Inline-6 cylinder aren't they?

AJ

 

Yeah I've heard of the solonoid too where it actually disengages the valves. I asked a few mechanics at my work but they kinda gave me mixed answers. I've never been able to look at one because they only made it in 81 and by 85 all of the engines in North America had been documented as being replaced I believe.

 

threre are some still out there, i've worked on them. Just haven't opened one up. but i have seen several

 

How much gas would you save cutting your power in half? Wouldn't the engine have to work harder to get your thirdgen up to speed anyway? I mean, I'm sure it can help, I'm just curious as to how much.

Of course, the real mileage saver is probably that it keeps you from mashing the pedal. The power ain't there so ya don't try, hehe.

 

I think this idea was for steady highway driving, so the HP required would be small.

 

Yeah, it is, along w/ fleshy rained on roads that get no traction. It doesn't seem to hurt it, but it is very powerless. Flipping the switch for all 8 is like hitting a nitrous button.

 

Back in the '70's when the fuel was scarce in the US, Crane came out with a system which turned V8's into V4's.

The kit included 4 weights to take the place of the pistons, 4 high domed pistons that bumped compression to (IIRC) 16:1, and a special cam shaft.

The 16:1 compression was there to compensate somewhat for the loss of 4 cylinders; the cam was ground such that the intake charge wasn't enough to fully fill the combustion chamber in order to aviod detonation at this high compression ratio.

I don't think this ever made it to market. I have the article in my archives someplace.....

 

It won't work unless you deactivated the valves on the same cylinders you shut the injectors off. The engine spends quite a bit of energy just pumping air in and out of the cylinders. If you just shut off the injectors you're still pumping the air through, still spending the energy, but getting nothing in return. In other words, you're just working the remaining 4 cylinders that much harder.

By leaving those valves closed, however, you're not pumping any air- you're just compressing and expanding the same air over and over, which takes, in theory, no energy (what you spend compressiong the air you get back when it expands again).

As you can imagine, oil gradually gets past the rings in that cylinder and makes a heluva mess, which is why all modern computer controlled systems drop cylinders randomly or in a predetermined pattern- making sure each has some "run time" to keep it clean.

 

I would think that if cutting off one side would cause an unbalance, which in turn would cause premature bearing failure since the loads are not equal. That and the oily mess damon was talking about. without the explosion pushing the rings against the wall im sure that you would fill the cylinders with a good amout of oil if your doing a long highway cruise. That and the fact that liquid doesnt compress...if by any weird chance it happens to fill with enought oil to fill the compression stroke.....somethings going BOOM