Engines That Shut Down Cylinders For Fuel Economy

[bahanthich]

its probably a stupid question, more out of curiousity then wanting to actually do it, but is it possible to shutdown 2 or 3 cylinders while driving for fuel economy? ie turn off some of the injectors temporarily or another way? im sure its not that simple and theres probably some bad effects on the engine/fuel system which is why no one does it, but if someone could explain why its not possible i would be interested to know. i was thinking of a 8 cylinder engine i read about a while ago that runs on half its cylinders to save fuel economy until you floor it, and then it runs on all the cylinders.

theres a bit of information on the internet about it 'firing on half-cylinders' or 'cylinder deactivation' but im interested if its possible to implement a similar thing on standard cars.

[Guilt-Toy]

its all in the ecu.

The new computer from ray hall would probly be capable of doing this if they wanted too.. i dont think there are any aftermarket ecu's that do it at the moment.

Make one. let me know how you go

[Shakiel]

Its both electrical and mechanical

From what i've kind got to understand its actually the valves on the particular cylinder being held open through the use of oil, flow of oil to hold the particular valves open obviously would be commanded by the ecu once it knows the car is at a cruising point where it can shutdown cylinders. i had it explained to me a few weeks ago but i forgot how and what actually happens. we were talking about it at work today, its how I kind of remember.

i think maybe its like vvti, vtec? where the valves are open for a little longer at higher rpm, but instead constantly held open

dont quote me on this either, as im not 100% but will definately find out again.

Apparently this function is already in the VE commodores, but due to vibration are not enabled.. so we'll most probably see it on the next series once they have their vibration problems sorted.

Edited May 21, 2008 by shAkIeL

[bahanthich]

what im interested to know, is just say you can make a switch that turns off three of the injectors, and use this switch when you dont need power (ie driving in traffic) im pretty sure you can turn off injectors using a laptop connected to consult port, but if you do this, is it safe for the engine, and would it screw up the fuel mixtures etc? i would have though if half the injectors are available, half the fuel is being delivered, and its in proportion so it should still run ok but with much less power? or is it more complicated then that?

some information on the net says the engines that have this done (using the physical system on the valves of the cylinders), get up to 20% more fuel economy.

[unique1]

unplug 3 injectors and set how it runs lol, not ideal at all u will be lucky if it runs at all

[Rolls]

With factory cars that do it they keep the valves open, as if you just turn the injectors off you will still have mechanical loses from compressing air. It will also run incredibly lumpy and probably not idle properly.

Basically dont bother unless you feel like engineering a head that can force the valves open.

[Kranker]

What i do know is that the system in the Chrysler 300C actally alternates which cylinders are shut down, otherwise you would have uneven wear within your engine.

And according to reviews in some major motoring publications, it doesnt really give a dramatic improvement in real world economy.

Its still all new technology so I dont think we're going to see any real improvement in fuel economy from cylinder deactivation for a couple of vehicle generations yet.

I think its only a sales gimmic...like hybrid cars. Pseudo-green cars.

In my opinion you want economy go buy a new diesel golf. (i die a little inside when i suggest someone buys a diesel).

Would be a laugh to try it, pick up a sh!t box from a wreckers and wire a switch to deactivate 2 injectors like you suggested. Just dont spend any money on the thing.

[Adriano]

Dont forget that most EFI cars turn all the cylinders off under decel

[JustinP]

I think it's a stupid idea, just for marketing really at a time when people are more fuel conscious. All that mechanical energy is being wasted by driving the inactive pistons, its just stupid. I like the idea of having a smaller capacity turbo charged engine, and using right foot to lower consumption.... Not that that actually ever works in real life hehe