[Matra et Alpine]

Originally Posted by hightower99

Honda VTEC systems have been able to change timing since 2001 (2002 in the US) with i-VTEC.

Need to keep up to speed with innovations if you want to be designing your own, ht Honda's latest is A-VTEC and patent was published over a year ago.

While BMW certainly trumped the rest of the market on getting such a system into production, Honda’s additional years of research seem to have paid off with several advantages. Take a look at the drawings here - BMW World - Technology You will notice several things about BMW’s application. First, Valvetronic increases the height of the valvetrain and cylinder head quite substantially. Second, BMW’s intermediary actuator (I can’t quite call it a follower) is quite large, adding extra moving mass in the valvetrain (perhaps explaining the rpm limitations of the first generation Valvetronic engines). Finally, BMW’s implementation does not alter valve timing by moving the cam centerline. This means that in order to optimize low lift valve timing, BMW’s VANOS VTC system _must_ be applied as well to advance valve opening. By comparison, VTC control seems far less critical on A-VTEC. So, in summary, reduced size, mass and self regulating VTC all would appear to be advantages of A-VTEC over Valvetronic