cylinder shut down tech, how does a V8 run on 3 cyls?

[MS112]

I think one of the main reasons for a petrol engines higher part-load fuel consumption is due to the butterfly valve correct? The number of cylinders isn't the full issue; what needs to be fixed is the way a petrol engine is governed.

[Duk]

I think one of the main reasons for a petrol engines higher part-load fuel consumption is due to the butterfly valve correct? The number of cylinders isn't the full issue; what needs to be fixed is the way a petrol engine is governed.

You're on the right track MS112. http://www.autospeed.com/cms/A_110216/article.html. At the end of this article, the writer sugests using exhaust gas recirculation so that a larger amount of throttle (lower engine vacuum and so lower pumping losses) will result in better Brake Specific Fuel Consumption (More power per Kilogram of fuel burnt) during low throttle (cruising) driving.
It look very interesting and I see a valid method of getting a petrol engine close to the BSFC of a diesel by using the bennefits of electronic throttle control.
Whether this is better or can be used with the Cylinder shutdown/Displacement on demand engines will be interesting to see.

[o_man_ra23]

Good use of the word 'supposed' in the net effect of energy loss - as many would know that no real world application of energy conversion is perfect.

True that the practical application of energy is not ideal. But... the spring effect, with a heated cylinder (read good ring closure) wouldn't be too bad at all. Leakage would be minimal, and thus the energy stored during compression/decompression would be reasonable, making the net losses low. These losses would would be there anyways though, so by having the same compression losses, more efficient burning in the other cylinders, and the same power requirements, a fuel saving can be made. 20% is indeed a big claim, and I also am skeptical of that, but there could well be a significant reduction in cruising fuel consumption.

[Grega]

i found where it was : http://www.gm.com/automotive/gmpower...ch/pdf/DoD.pdf

[Grega]

i emailed the GM Powertain division.

[SeptemberSquall]

example:

2008 model year honda accord 3.5L v6 sedan with cylinder deactivation adr81/01 10.0L/100km 202kw 91RON
2006 model year toyota aurion 3.5L v6 sedan with dual vvt-i adr81/01 9.9L/100km 200kw 91RON 204kw 95RON adaptive mapping

in addition, dual vvt-i benefits not only fuel economy, but also smooth idle, improved midrange torque performance, etc. i'd like to see turning off cylinders improve both economy and perforamnce. haha

[3sgte]

i found where it was : http://www.gm.com/automotive/gmpower...ch/pdf/DoD.pdf

Do you have a copy of that PDF?
If so, I would really like to see a copy.

I have a dead link here.

[3sgte]

example:

2008 model year honda accord 3.5L v6 sedan with cylinder deactivation adr81/01 10.0L/100km 202kw 91RON
2006 model year toyota aurion 3.5L v6 sedan with dual vvt-i adr81/01 9.9L/100km 200kw 91RON 204kw 95RON adaptive mapping

in addition, dual vvt-i benefits not only fuel economy, but also smooth idle, improved midrange torque performance, etc. i'd like to see turning off cylinders improve both economy and performance. haha

It is my understanding that by using the Dual VVT-i, they can achieve an Atkinson like effect (longer expansion stroke) which has a similar effect on efficiency as increasing the load in the non-deactivated cylinders of a car with cylinder deactivation. With VVT-i they can also achieve internal EGR via the valve timing. Finally, those 2GR run a fairly high static compression ratio to allow the efficiency via this playing around...

Note that all the engines (not sure about the Merc) which use deactivation do not have the ability to vary the timing independently for the intake and exhaust camshafts.

I've made myself curious, I want to go and stick a vacuum gauge on the manifold on one of those 2GR and see what it tells me. I bet it would be interesting.
Anyone have one of them?

[timbosaurus]

This has been bugging me for a little while and i wasnt sure why. First off, what are they?

I don't know the official values on both drive cycles in L/100km, and even if I did, North America and Australia run different drive cycles anyways.

As I said, I'm talking about practical figures, and by that I mean I have had the pleasure of a lot of driving in both the VE SS, and the G8 GT... the comparible models.

The difference in actual figures is outstanding. In my experience between 10 to 30% on similar driving.

Yes, when cylinders are de-activated there is a comprimise in balance and smoothness... as expected. There are technologies that many companies implement including active engine mounts, variable inlet length, and exhaust flapper valves, all used to tune in/out resonances.

So in my experience, yes, it's more than just marketing hype.

[brett_celicacoupe]

Good use of the word 'supposed' in the net effect of energy loss - as many would know that no real world application of energy conversion is perfect. Im sure that they theoretically measured the differences to determine the 'best' solution but i wonder how they would have validated their results. Being involved with a project that must prove a 1% fuel efficiency increase when there are so many factors that contribute to it (the list involved about 20 factors) then that is very hard to measure.

im curious about top end lubrication. no fuel means no lubrication.

though maybe this isnt a problem since the valves dont open

[allencr]

So in my experience, yes, it's more than just marketing hype.

The engineers would be slitting their wrists if they had to go through all this BS for zero gain, but glorious marketing. I just think it's easier to market this kind of crap to wealthy fools that want power and also want to have a 'warm & fuzzy' feeling about conserving fuel, saving the earth, no matter how small the gains & complexity.

[MS112]

It is my understanding that by using the Dual VVT-i, they can achieve an Atkinson like effect (longer expansion stroke) which has a similar effect on efficiency as increasing the load in the non-deactivated cylinders of a car with cylinder deactivation.

I think (even in my limited experience) that continously variable valve timing would provide more benefits than cylinder deactivation. However, this would require valves which are controlled by a computer, not by a mechanical camshaft. I found this to be an interesting report on the design of a camless engine valve system.

Also, something else that bugs me: a diesel engine operates on the idea that you inject the required amount of fuel for the required amount of power. This in effect governs the engine speed. Why can't this princible be applied to the petrol engine?