CAHobbs

While I was surfing the net, I came across this little bit of information. After reading it I was a bit surprised to say the least.

It has to do with the something called the "Honda's Variable Cylinder Management system".

Here's what the article said:

Maybe some of our members can explain this system better to me and verify that this takes place in our 3.2s because I wasn't aware our engines could shut down cylinders like some of the GMs could.

I can't imagine we run ala inline 3 cylinder mode as the artical states... imagine telling someone who's trying to race you, to back down or your going to open up another 3 cylinders of woopass on them!

Any clarity would greatly appreciated!

Happily Confused!

ussi

iTrader: (1)

i'm curious too

T Ho

VCM is only available in the Accord Hybrid, Odyssey minivan (Touring Model only, IIRC), and some version of the Pilot, I think.

Basically, what happens is the i-Vtec is setup to completely shut off the valves for the disabled cylinders. At the same time, the fuel and spark for those cylinders are shut off. This removes the pumping losses from these cylinders, not to mention the heat loss (and therefore economy loss) associated with burning fuel in additional cylinders. I think it's responsible for about 6-8% fuel economy gain.

I do wish my 6spd had it. The car is geared high enough, and is aerodynamic enough, that it could take great advantage of the system, I would think. There are probably NVH (noise, vibration, harshness) issues to work out before they run it up the Acura line, though.

lil12002

werd i know its in the touring odessy's...

Anansi

Yall got it pretty much right. We have it in our Odyssey and it's kind of cool to know that you've just shut down half of the engine and that your mileage is improving. It wouldn't work for racing though. It only shuts the cylinder bank down under low stress situations (ie: cruizing at a steady speed on level or downhill roads). Hopefully if you were racing someone, you'd keep the revs up enough to prevent the engine from shutting down your other 3 cylinders.

Atrain

You want the valves open, not closed. To reduce pumping loss, you have to eliminate the compression. Hanging the valves off the seats would do this.

I believe the engineers just shut of the injector pulse width and spark to the cylinders. Saves maybe 1-2% economy.

The problem in all this is the closer an engine runs to it's adiabatic efficiency, the more efficient it becomes. Shutting down 3 cylinders drops the heat factor which makes the engine run cooler. If it drops below adiabatic (which is most likely will do), then you lose efficiency and economy.

Try a colder thermostat and see what happens. The cooler it runs, the more fuel you'll use. It also keeps you less knock constrained which means, in theory you can add more spark timing and make more power.

A-Train

F23A4

Touring and EX models.

trancemission

This is off topic and needs to be posted in Car Talk.