cylinder shutdown

[dt8068]

Alright, I'm probably gonna get flamed for this, but...

Would it be safe to unplug the injectors and coils for every other cylinder in the firing order to get better gas mileage for long highway trips; kind of like chrysler and GM do with their V8s?
When I did the valve cover gaskets a few months back my friend forgot to plug in the coils on the left cylinder bank, and I started the car, without realizing it. It idled rough, but over 1500 rpm it was smooth again. it took us about 30 seconds to realize the mistake, we plugged the coils in and all was well. (hopefully it didn't do any damage) This gave me the idea of the cylinder shutdown, and whether or not it would be harmless to run on 4 cylinders. The check engine did not come on nor did it throw any codes, which was weird, but probably because we didn't run it long enough for the ecu to realize something was screwed up.

I would like to do this for long trips to and from school, but something tells me the car will have a fit electronics wise.

Opinions? suggestions? (besides sell the 540 and buy a 525i)

[632 Regal]

you will ruin the piston rings and rod bearings in short order, perhaps the wrist pin and piston too.

[dt8068]

I don't see how this could do any mechanical damage, the bearings are still being lubricated, right? Does the fuel provide lubrication for the cylinder rings? I could be completely wrong but it seems that the main problem would be the engine having to overcome the compression on the non-firing cylinders, and therefore it might be a useless idea for better mpg.

Do those chrysler V8s open the exhaust valves full time for the shutdown cylinders, because that seems like it would be the only way to justify cylinder shutdown.

-again, flamesuit on.

[Fetch]

fuel either lubes or cools down, or both, the cylinders, I'm not positive.
I believe the exhaust valves do open up on those newer cars.

Have you ever driven a car that isn't running on all cylinders?.....It will barely move! lol

No flamesuit necessary, I understand where your idea comes from.

peace

PS: you should be getting 25-28mpg on the highway, which is pretty sweet for a '94 4 liter engine!

[dt8068]

yea, I get just over 25 mpg highway, which is pretty good for a v8, especially with 200,000 miles.

Its just that I live in Philly, and go to school in Florida, and even though my gas mileage isn't bad, when I head home for summer and winter breaks that 2200 mile round trip is a lot of $fuel$. I would run on 4 cylinders for this drive only because it's boring, and I cruise at a constant speed for 15 hours.

[whiskychaser]

Old motorbikes used to have a decompressor valve to help you kick them up. So yeah you have no compression, spark or fuel. What happens when you hit a hill?

[Barney Paull-Edwards]

M-B used to make a diesel that cut out cylinders via a cam on the fuel pump,there was no rack to increase the stroke of the pump, seemed to work pretty well, ask anybody charged by an "E" boat! Surely friction will negate any fuel advantages?

[Ross]

scott h had a miss on 1 cylinder for a short whike and the rings were completely shot. How do you figure?

[Barney Paull-Edwards]

Lets say you cut 4 cylinders then those 4 pots are being dragged round by the other 4 as well as them trying to drive the car, if you see what I mean. It should be possible for one of the whiz-kids like jon k to devise a system to alternately cut pots on low load surely?

[Ross]

The engines that selectively shut down cylinders also leave the intake valve closed. Without doing so you are still compressing every other stroke.
There may be consequences to the ECM from unplugging the coils. I don't think unplugging the injectors would damage any electronics though. You're still going to have pumping loss operating dead cylinders so doubt you'd see any economy in doing so.

[Barney Paull-Edwards]

Agree with that, it was the reason the chev/chrysler(?) was a failure,big diesel can absorb the pumping losses. It makes more sense to me to maximize the efficency of what you have and use the gauge below the rev counter.Not really a good comparison but if i have a mad moment with clean oil and filters then the OBC can read 57 as opposed to 37 normal or 27@147. If clean oil makes such a difference in my diesel then it must make a difference in a petrol too?

[filip00]

sell the car to a little less stingy bmw fan.

[dt8068]

I would never sell the e34, and when it dies (if it does) I'll keep it for parts for my next e34.

I was just thinking of crazy ideas to maximize the efficiency of my 1100 mile drive to and from school, but it seems its not worth the trouble, or the chance of ruining a good engine.