Here is something interesting...<P> <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><BR>On April 4, Toyota Group parts maker Aishin Co., announced that BMW had placed an order for its Variable Valve Timing (VVTi) unit which controls engine valve operation. <P>VVT is a system which automatically maintains the optimum amount of air flow through the intake and outlet valves according to engine revolutions. Aishin supplies the majority of its VVT units (called VVT-i by Toyota) to Toyota who employ this technology across most of its engine lineup from the 1.0 liter to the 4.3 liter V8. <P>Preceding the BMW deal, Aishin has already been supplying this technology to Volvo (CVVT-Continuously Variable Valve Timing) and Renault (VVT-2 Stage Variable Valve Timing). The high efficiency levels of Aishin's VVT hydraulics and the fact that the component is between 30-50% lighter than those of rivals' ensures that orders stream in from manufacturers looking to minimize weight in engine bays. And under the name "Vanos," BMW has also decided to incorporate this technology to improve fuel efficiency and reduce emissions. <P>Aishin will supply 200,000 units in 2001 with a goal to expand to 800,000 by 2003. Utilizing the strong PR of the BMW order, Aishin will aggressively approach other US and European carmakers in the near future."<HR></BLOCKQUOTE><P>Volvo's CVVT and Toyota's VVT-i are both "Cam-Phasing" variable valve timing systems unlike Honda's VTEC which is a "Cam-Changing" variable valve timing system. The advantage of VTEC is that it has high top end power, but not much improvement in torque. VTEC is also noncontinuos and has a maximum of 3-stages. That is why it has an on/off feel. No other VVT system can vary valve "lift" like VTEC, besides Porsche VarioCam Plus.<P>On the other hand, Volvo CVVT, Toyota VVT-i, and BMW Double Vanos are less heavy, expensive, and complex. This type of VVT improves torque across the entire rev range and it is continuous unlike VTEC. But this system does not have variable valve lift and valve opening duration, with the exception of Porsche VarioCam Plus.<P>The only companies that use "Continuous" Cam-Phasing VVT are Volvo, Toyota, Jaguar, and BMW. The rest of the companies with "Cam-Phasing" VVT use 2 or 3 stage discrete phasing.<P>The Volvo 4 / 5 / 6-cylinder modular engines use either inlet or exhaust, continuous variable valve timing.