New Chevy Impala?

[Shibby]

I just saw a commercial for it. What was interesting was that in ran on 4 cylinders for economey, but could change to 8 cylinders for power. I'm curious how this works and if it sounds like a huge problem waiting to happen.

[metalmarty]

From what I've read, the variable displacement does not do all that much for fuel economy... but it depends- I've also heard that the new vette gets around 30mpg. It seems to work better in lighter cars than in trucks (which is all I care about really), so the Impala probably does okay. However, I think the new Impala is great for two reasons - 320hp and rear-wheel drive. Good ol' Chevy!

[metalmarty]

Oh, in reply to how it works, variable displacement works by disengaging four cylinders at cruise speeds (overdrive). Once the engine is presented with a full load (downshifting) all eight cylinders are engaged for maximum torque. And about it being an accident waiting to happen, it failed in its early stages (the Cadillac 6.4 liter), but the new engines seem to have the bugs worked out. As for me, more options means more is likely to go wrong.

[jwoody]

Oh, in reply to how it works, variable displacement works by disengaging four cylinders at cruise speeds (overdrive). Once the engine is presented with a full load (downshifting) all eight cylinders are engaged for maximum torque. And about it being an accident waiting to happen, it failed in its early stages (the Cadillac 6.4 liter), but the new engines seem to have the bugs worked out. As for me, more options means more is likely to go wrong.

I can see how the computer could tell the injectors not to spray to those 4 cylinders when they are shutdown. But how do you keep the pistons from continuing to compress. Or is this of no real concern? I figured you wouldn't want the pistons to fire dry.

[beefcake]

I can see how the computer could tell the injectors not to spray to those 4 cylinders when they are shutdown. But how do you keep the pistons from continuing to compress. Or is this of no real concern? I figured you wouldn't want the pistons to fire dry.

The other pistons will pretty much be doing nothing and just be driven by the power of the crank from the other cylinders. There is no spark in those cylinders either. The hemi's have this system as well. It seems to be pretty perfected though.