Somewhere, there's a perfect balance between horsepower, throttle response and clean emissions. Nissan Motor Company's come one step closer to finding it. It's getting there partly because of its newly released Variable Valve Event and Lift (VVEL) technology and preexisting Continuously Variable Valve Timing Control System (CVTCS). So far VVEL is scheduled to appear only under the hoods of 2008 G37 coupes, which will feature the all-new VQ37DE engine. But more important than which cars are slated for VVEL treatment - since most all Nissans and Infinitis will end up with it sooner or later - is exactly how it works, and just as important, why you should even care.
Nissan's already offered Variable Camshaft Timing (VCT) was introduced on the preceding Z's VG30DE engine. An electric solenoid controlled by the vehicle's ECM triggers the VCT, which alters valve timing but not lift or duration like other systems. And then there's Nissan's version of VVL (Variable Valve Lift), which uses hydraulic pressure to lock up two different sets of camshaft lobes, effectively increasing lift; it also controls valve timing and duration. It's similar to Honda's VTEC.
But VVEL is different. Of course, Nissan's latest valve timing control system is good for more horsepower, otherwise you can bet we wouldn't be bothering to tell you about it, but it also does other important things like improve throttle response, fuel economy and emissions output, arguably things we all care about. Besides managing valve events, VVEL renders the more conventional throttle plates useless ... almost (they remain for emissions reasons, however); that's because the VQ's intake valves instead determine how much and for how long air is introduced to the cylinders during low and mid engine speeds. BMW comes to mind here, and yes, the Germans developed this first and called it Valvetronic, but VVEL is different and, if you ask Nissan, better. They want you to know why.
VVEL controls the incoming charge at the intake valves, and CVTCS manages all of the 24 valves' up and down characteristics, specifically lift and duration. Like other manufacturers' variable valve timing systems, Nissan's VVEL keeps the intake valves open for a shorter period of time during moderate driving conditions. This reduces the chance of the air/fuel mixture blowing back the wrong way, which means a more complete burn and hopefully more torque. At higher engine speeds the system allows the valves to open farther and for longer periods of time where the likelihood of blowback is reduced due to the increased air velocity; this results in additional top-end horsepower (read: The stuff that makes us care about VVEL in the first place). A rather unconventional-looking rocker arm paired with two special links is responsible for moving the intake valves. The rocker arm imparts its motion onto an eccentric cam mounted on a small, rotating driveshaft to make this all happen. Output cam movement is varied through a rotating control shaft inside a mini DC motor; this effectively alters the rocker arm links' fulcrums for constant valve lift adjustments. Sounds complicated. It is.
Compared to what those Germans concocted, Nissan claims 32 percent quicker responsiveness with its VVEL, 52 percent less parts per cylinder and a 20 percent smaller design overall (For now, we'll have to take their word for it, but we're guessing the new VQ's heads have got to be a heck of a lot bigger than the old ones to fit all of this). We don't mention this to disparage BMW's pioneering efforts and proven technology, but it's worth noting anytime the same job can be accomplished using fewer and smaller components. The new VQ37DE is said to produce 330 hp and 270 lb-ft of torque. Some of this is likely attributed to the added 0.2 liter of displacement and redesigned cylinder heads, but we're sure VVEL also has something to do with this newfound horsepower. Peak torque gains are minimal in comparison to its 3.5L predecessor - only 2 lb-ft - but it's worth mentioning the 6 percent increase in torque down low and 4 percent increase toward the top end. These are exactly the types of torque gains we'd expect from valve timing adjustments.
And then there's the green stuff. VVEL isn't just good for horsepower, it also creates a cleaner burn. The VQ37DE is said to burn 10 percent less fuel and, in turn, emit fewer carbon dioxide emissions. During low- and mid- engine speeds, the intake valves serve as the throttle control, not the throttle plates inside the two throttle bodies. By controlling the intake charge closer to the combustion chamber, air travel is eased, which contributes to lower emissions. As mentioned, intake valve lift remains low at these speeds; this reduces valvetrain friction - mainly at the camshafts - which also reduces emissions. Nissan considered intake valve timing during start-up conditions also, when the catalytic converter's still cold and not working as effectively. Intake timing is optimized here to build exhaust heat quicker, essentially making the cat work sooner. Additionally, hydrocarbons are kept minimal through less intake valve lift during lower engine speeds. The lower valve lift helps promote additional airspeed, which creates a fine mist of fuel for more complete combustion. Makes sense.
We're looking forward to getting our hands on one of Nissan's new 3.7L VQ's. The 3.5L V-6 has already proven itself to be a monster once turbocharged, so we can only imagine the repercussions of bolting on, say, a couple of hefty-sized, ball bearing GT turbos from Garrett backed by the new VQ's added displacement and VVEL. Should be nice.