Running a V6 on less than 6 cylinders

[charlie_pank]

I know that newer BMWs have a system for this to increase fuel economy when cruising. What would happen if I simply removed the injector plug from a couple of injectors on my V6 when going on a long steady journey? Obviously I'd have less power but better fuel economy.

 

Which 2 (or even 3) cylinders' removal would make for the smoothest running under the circumstances?

 

Would there be any long term (bad) effects resulting from cutting the fuel to some of the cylinders?

 

back here because I want to be.

 

Edited by - charlie_pank on 29 Mar 2010 12:20:09

[Irrelevant]

Nice idea but doubt it would work unless the ECU was mapped to do this.

Can't think of any harm though.

 

 

Edited by - Epimetheus on 29 Mar 2010 12:25:39

[charlie_pank]

Sorry, I don't understand. It's 1 injector per cylinder. So how will the mapping affect this?

 

What wouldn't work about it?

 

back here because I want to be.

 

Edited by - charlie_pank on 29 Mar 2010 12:27:53

[peterg]

The system may well go into limp home mode or even refuse to run if it detects a missing injector...

[Nigel Fox]

Your engine would be using energy to compress air in the non working cylinders.

If there is a Lamda sensor, excess air would be detected in the exhaust, presumably causing the ECU to richen the running cylinders.

 

Full time class 4 Zetec

[charlie_pank]

Both good points. Perhaps a more cunning cylinder shutoff mechanism is required!

 

back here because I want to be.

[Irrelevant]

Actuially . .. maybe I'm talking bollox again 😳

 

My thinking:

6 cylinders pull 1 car at X speed consuming Y fuel.

 

Removing let's say 2 injectors does not mean you can reduce fuel consumption by 2/6 of Y because you still have to pull the same car at X speed. So the ECU has to increase fuelling for the remaining cylinders. Whether the ECU can increase fuelling within it's mapped parameters will dictate whether it can cope with the loss of cylinders - I guess it will have trouble. MIght be OK in the cruise but when you need to go up a hill, it will be liable to run lean.

 

Try it . .. would be nice if the ECU gave you a warning light if the mixture goes too lean though.

 

I bet these modern engines that loose cylinders have mindblowingly complex mapping and logic controlling them. I know that Busas have a different fuel and ignition mapping for every gear and cylinder. I guess if you had this, and the ECU could reliably decide what mode the car was being driven in, it could start cutting cylinders when cruising.

[Irrelevant]

Your engine would be using energy to compress air in the non working cylinders.

 

Oh yeh . . good point . . . how the hell do they cope with this then? Does the variable valve timing allow gas straight through without compressing it then? How else could they do it

[IKB]

Wouldn't the ECU shut down the injectors to the redundant cylinders?

[I reply to every thread]

Yes - Otherwise you'd get horrendous borewash and the engine would last about 200 miles

[I.Mupferit]

I believe the system also varies which cylinder is shut down on a continuous cycle, so in effect, they all share the work - as it were. Just pulling plugs off injectors is a bad idea that won't save you anything.

 

 

[elie boone]

The cilinderhead would heat up unevenly, this could lead to all sorts of problems.

You can improve a lot on fuel consumpion with the right tyre pressure and a adapted driving style.

[Allen Payne]

The wiring to one of the injectors on my VR6 failed once and it ran horribly, it got me home but it was horrid to drive.