[Joenavy85]

IMHO the more you change something the more likely it is to fail. The Engineroom i worked in had quite a few solenoid valves for various different functions, when one burns out (about once every 2-3 months) the function is lost for that piece of equipment until it gets fixed. So on a car engine you make them spring shut, now when the coil burns up (probable when you figure at 1700 RPM it opens 850 times a minute (~14 times per second)) your exhaust valve is stuck shut, and that cylinder is now making no power, not to mention pumping losses (i figure a 15-20% loss of power on a V8, more so with fewer cylinders). burning out a coil would be the equivalent of breaking a push rod.

NOTE: I am in no way at all doubting the FE gains of this type of system, only pointing out potential issues with it. I personally don't want the gains at the risk of burning out a solenoid coil and then having to pull the head to repair it. Yes i know, if it's new it's under warranty, but how many of us dispose of a car as soon as the warranty is up?