Hi Guys,

Last night I remembered that Honda advert (not sure if you have it there) basically a V6 (maybe Straight 6) that can run on 5/4 or even 3 cylinders...

Given high gas prices and the will to do as much for the environment as possible I thought why cant we do this as well?

Any technical reason (apart from lean AFR's and the cat) why we cant do they same thing?

Basically we would cut fuel to 1 cylinder during hwy cruise conditions.

We might have to make it a bit more complicated than that, ie rotate which cylinder we cut fuel to... But that's the general idea!

Cheers
David

 

I don't see why you wouldn't be able to do it. If you had a misfire you would only run on 3 cyl's and you can do that for extended periods of time with no motor damage

I think thats the new calling for ecu programmers like yourself! Forget HP, gimme MPG!!!

 

I thought of this idea already, then I saw that Honda had it on a V6 model. My idea was to rotate the missed cylinder as to ensure everything was symetrical in case there was accellerated wear or higher cylinder temps over it.

Great minds think alike.

Ha, like either of us have enough time to undertake such a project.

I would be interested if there is a patent on this.

 

Can this even be done on a inline motor? I would think the balance would go to shiat. Of course, I'm not an engineer...

I believe dodge also does this with some of their V8's.

 

Im down... Ill test it too! It would seem you almost would have to cut 2 cylinders for the balance.

 

article about this on Honda:

http://www.greencar.com/features/features46/

Last couple of paragraphs are of most interest...

 

This is nothing new...wasn't Cadillac's Northstar one of the first engines to do this like 15 years ago?

Anyway, I think the question would be: Would this really save much gas? If you cut 1 cylinder on our 4 cylinder engine, you're removing 25% of the power to rotate the crank, so if the momemtum of the other 3 cylinders can make up for that by consuming less than 25% more gas, then we would save gas, but how much? I can see where it would make a difference on a V-8, because at cruise, you don't need 8 cylinders to produce enough power maintain the cruise. Each cylinder probably can't get to the lowest threshold of gas use to maintain the cruise, so it simply wastes gas, if that makes any sense.


Eric

 

Interesting. I've been thinking about fuel economy for the last week as well. Why dont we maximize what we have. How about Alt map fuel economy mode with fuel efficient ignition/fuel/mivec maps? Tephra, does alt map currently support an entire set of maps with a mivec map or just fuel/ignition?

 

What would the difference be between alternate maps for fuel efficiency and tuning the cruise areas of the maps we already have?

Cutting out a cylinder under cruise sounds pretty cool

 

Isn't the balance already shiat on an inline 4? I think that's why we have balance shafts.

Seriously, though, the firing sequence is 1-3-4-2, yet the 1+4 move together and 2+3 move together, so the firing order already would imbalance the motor. I don't see how rotating a cylinder cutoff would produce any more problems, but I don't know for sure, either.


Eric

 

The reason you do this is to decrease pumping losses. IE the losses induced when the engine draws on manifold vacuum. Vacuum is not free, it costs energy. The closer you are to 0 psig manifold pressure the more efficient the motor is. Actually the more manifold pressure you have the more efficient the engine is (as the manifold pressure will force the piston down on the intake stroke instead of vacuum pulling it back up).

Anyways the biggest issue WAS that the ****ty fuel in the day would clog up on the injector tip. They have since then added detergents so that this is NOT an issue.

Maybe somebody can look into this for me but I believe you have to hang an intake and exhaust valve open so that the piston can move up and down with less restriction. IE: your still doing the intake and compression of air (without the fuel) which is the energy we talk about when we say "pumping losses". Thus all you really do when you shut the injector off is reduce engine power, not reduce pumping losses.

Thats just what I have on the top of my head, and I'm 6 beers deep so please excuse the poor penmanship.........

 

The motor would still be in mechanical balance because the pistons and balance shafts are still moving. An I4 is balanced in first order vibrations, not so much in second, third, fourth, etc... vibrations. Thus the need for the balance shafts. Its a moot point though because as I said, we still have mechanical balance. I don't think the cylinders that are burning have much to do with balance AFAIK.

As compared to an I6 which is balanced in first, second, third, etc.... order vibrations.

 

Yeah, yeah, I want to be able to shut off 3 cylinders by the flip of a switch and make my EVO sound like a Subaru.

 

Actually, to add to that...

Cut your spark plug wire and wire in a switch...route that to the cabin and when you want to shut off one cylinder, flip the switch!




Just kidding...

Edit: Actually, it really isn't a bad idea...except do it from the ECU just like the NLTS switch but I guess the easiest would have to be what you said about using the TPS, RPM, Load, and Vehicle speed to shut off a cylinder.

 

The other issue with just cutting fuel to a cylinder or two cylinders is compression. The cylinders are still moving and the valves are still opening and closing. There is a lot work that goes into compressing the air. So not only are you cutting 25% of the power contributing to rotating the crank, sliding the cylinders up and down, and all the other power draining components, you still have the one cylinder doing a compression stroke with out any benefit in the end. The other three, two or how ever many cylinders have to compensate for that work also.

The optimum way would be to some out disconnect the "dead" cylinders from the crank and there you go. (not possible)... the next best solution would be to change the valve timing such that there is never a compression happening in the "dead" cylinder (is possible with some very tricky valve-train....)