Robert McElwee wrote: > I'm wondering what the > effect would be if I killed fuel/spark to two of the cylinders on a > Miata while cruising around 50-55 MPH. Anyone want to venture a guess?
Big time pumping losses. You're still going to be compressing whatever gases end up in the deactivated cylinders. The way the new GM V8's that do cylinder deactivation work is that they close *all* the valves to the offline cylinders. So you're spending energy compressing the gas, but it's basically an air-spring and you get it back on what would be the power stroke. It's been a couple of years since I heard the tech talks on this, but IIRC, they draw a charge, fire it, but never open the exhaust valve. I think they continue to spark. There was something about reactivating the cylinder every minute or two, but I don't remember the details. Mechanically, this is done with magic lifters that have a pin open to the side of the lifter. If that pin is in it's natural position, the lifter works normally. If you push it in, the cam side of the lifter can move without moving the pushrod. An extra oil galley to the sides of the lifters provides pressure to push the pin into the lifter and deactivate the valve. -Z _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower
