[quote author=azazel1024 link=topic=28995.msg400196#msg400196 date=1126263684]
Not entirely. AFAIK
Most of Honda's systems use multipul cams in conjunction with continuously variable timing control (in the case of the i-VTEC) or simply two sets of cams. The mazda unit does not change the lift by using multipul sets of cams, it only controls the timing control. This means that potential gains are more limited, however cost and complexity is much less. [/quote]
That’s why I said almost.* Look at my entire post above and you will see that I said essentially the same thing you did.* To summarize:
VTEC in all its implementations varies both valve timing and lift.* VTEC uses multiple camshaft PROFILES to improve low and high RPM performance.* There are two cam lobes (instead of the traditional one) actuating each valve.* Note that VTEC does NOT require multiple cam shafts.* The D15Z1 found in the 1992-1995 Civic VX is a Single Over Head Cam VTEC engine optimized for low-emissions and fuel efficiency.
DOHC VTEC is the system most commonly meant when someone mentions VTEC.* The Dual Over Head Cam VTEC has high and low RPM lobe profiles on the intake and exhaust camshafts.* A SOHC VTEC switches between lobe profiles so smoothly that is hard to tell when the switch occurs, but on a DOHC VTEC you can hear and feel the cam profile change while you are driving.
Toyota (VVT-i) and a number of other manufacturers came out with VVT systems that utilized more than two profiles for lift and timing.* In response Honda developed i-VTEC, which rotates the camshaft using hydraulic control to advance and retard valve timing.* I-VTEC engines thus produce more torque at lower RPMs than a standard VTEC engine.
The Mazda MZR engine featured in the 3 utilizes continuous Variable Valve Timing, but not Lift.* The timing is handled via a static camshaft attached to a cog, which can advance or retard the cam’s timing.* Mazda then utilizes a Variable Length Intake Manifold (VLIM) to increase the torque band on our engines.*
The MZR engine has a solid torque range from 3000 RPM to a little over 5000RPM while a VTEC has torque PEAKS around 2000 RPM and 5000RPM.* Most automotive critics consider Honda’s VTEC engines to be the best 4-cylinder engines available to consumers, but depending on how you drive you might prefer a different implementation such as Toyota’s VVTL-I or the VVT + VLIM used in our cars.
A full list of Honda and Acura engine codes can be found at: