LETS RUN ON ONLY 4 CYLINDERS... (and save gas)

[basslover911]

SO, how does GM get their cars to run on only 4 cylinders while on the freeway? (does it simply cut off the signal to the injectors and turns four of them off? Just that?)...

I was thinking maybe, just maybe, I could put in a switch and everytime I hit cruise control four of the eight injectors signal would be cut, therefore only runing four cylinders at a time (and saving probably 5mpg if not more on the freeway while going at a constant speed and with the cruise control)...

What do you think? Am i completley nuts?

 

[Lextreme II]

No... I have been thinking about this too.

 

[jibbby]

The GM Version Hybrid is equiped with the "Active management fuel system" which enables and ables fuel delivery when needed... It works like this - The fuel is cut off to 4 cylinders and when active that apparently is just enough power to propel the GM truck at freeway speed flat grades... As soon as the truck hits an incline fuel is immediately restored to all eight cylinders... Apparently, the truck has no balls when the fuel is cut which makes perfect sense... Also they mentioned there is an elecric motor to help assist in stop and go traffic when the fuel is cut... So in the end you got a smart fuel system that cuts off fuel in a timely manner not effecting the ride too much and you get the gas mileage like a 4 banger most of the time.... Very clever, but I would still like to test drive these GM Hybrids to make sure the truck is not so herky jerky or something...

So for our Lexus cars, we would need to incorporate this Active Fuel management system and also the assistant electric motor to even consider this... Also the GM Hybrid is equiped with a larger motor to perform this function. I think the GM hybrid Yukon is 6.0L, so I am not so sure if the smaller UZ's running on 4 cylinders would even make enough power to roll the car.....

Good thinking anyway fellas....

 

[Treynon]

Daimler Chrysler has a similar system called MDS I believe. Multi displacement system I think is what it stands for I used to sell dodge trucks that were equipped with it.

 

[basslover911]

Sure, but the thing is that I am going to turbocharge my sc400 to about 400whp, so at 3000rpm (lets say) I will have (let say) 5hp instead of 1hp so the power should be there.

Also, it will only be when I (a) hit the cruise control button and I know that there wount be that big of a hill and (b) maybe when I am not in the accelerator i.e. idle.

There would be more human imput with this type of system instead of the GM one, but then again I will make it in a garage and not with 10 other engineering guys

 

[1uzfekp60]

You would have to cut air inlet and spark to those cylinders with no fuel cause they would be running lean while the excess fuel was burned off causing possible damage.

Ken.

 

[jibbby]

What about uneven exhaust flow, ignition, etc..? I just don't see it happening.. These hybrids have alot of technology behind them...To take a conventional motor and rework it to run on 4 cylinders part time and make it all work well without causing the motor damage over time would be quite an achievement...

Best of luck baselover, and keep us posted if you do infact give it a go....

 

[cribbj]

FWIW, my 2007 non-hybrid Surburban has this 4-8 switching, although I haven't been curious enough to buy the manuals to try to understand how it works.

 

[gloverman]

early mitsi mivec MD engines cut the injectors to two cylinders when idling but they also open the valves on these cylinders to drop the compression. I beleive to make it worth doing the cut cylinders need to have their valves opened to remove the compression drag. From what I have read most late systems that try this have complex valvetrains to enable removal of the compression drag - cheers