Nissan’s 370Z VQ37VHR Cylinder Head and VVEL Continually Variable Cam Timing Technology, Technological Terror or Performance Breakthrough?

The VQ37VHR does retain twin drive by wire throttles but they mostly stay wide open, the only time they close is on overrun to help provide engine braking and if the engines ECU detects low vacuum in the brake booster reservoir. In case of emergency they can also help slow the engine in case the VVEL system has a problem.

Nissans complicated system is advantageous from a performance standpoint because it can optimize the valve events for the immediate driving conditions giving both more power with a wider powerband and better driveabilty over a conventional valve actuation system. In a simplistic explanation from an enthusiasts point of view, the VVEL system gives the top end power of a long duration and high lift racing cam at high RPM, the good torque and midrange power of a hot street cam at mid RPM’s and the smooth idle and crisp driveabilty of a stock cam at low RPM.

The Nissan 370Z's VQ37VHR engine uses VVEL and CVTC on the intake cam only

This complication also increases the VQ37VHR’s efficiency and greeness. Nissans VVEL system helps reduce emissions by eliminating a race cams fuel wasting, hydrocarbon spewing and rough idling characteristics during idle and low rpm operation. The VVEL system has the ability to eliminate the EGR valve with early intake valve opening at low RPM and light loads; this retains combustion gas in the cylinders, reducing NOX emissions by quenching combustion, cooling the combustion temperatures.

The engines idle and low speed running stability is also improved greatly at cold start by reducing valve overlap under these conditions. This helps reduce cold start hydrocarbon emissions and speed catalytic converter light off. Since most of a modern cars total emissions output is produced during cold start, this technology helps the 370Z burn clean with no sacrifice in performance.

The VVEL system uses a cross link to move the position of the eccentric that controls the motion of the rocker shoe that operates the intake valve.  By rotating the upper shaft and moving the link, you can control the amount that the intake valve is opened in an infinite stepless manor

The complex VVEL valvetrain also greatly helps improve fuel economy in ways beyond the obvious optimization of valve actuation for all driving conditions. The engines speed and output is largely controlled by ECU control of the intake valves, not the throttles. By not having the restriction of the throttle blade at partial throttle, fuel wasting pumping losses are reduced. By lifting the valves only the amount needed for the load demand placed on the engine, a lot of mileage robbing friction can be reduced at part throttle. Lift the valves less at part throttle and the valve springs don’t have to be compressed as much wasting less energy. The sophisticated valvetrain is the main reason for the 370Z’s 1-2 mpg improvement in fuel economy over the 350Z at 18 road and 26 highway mpg respectively despite the VQ37VHR having a 5.7% increase in displacement and a generous 26 hp improvement in power. It is also responsible for this high performance car having a ULEV emissions rating.