The Infiniti (and Nissan) faithful are plenty familiar with the VQ-series family of V-6 engines. The VQ V-6, which ranges in size from a wee 2.0 liters in foreign-market vehicles all the way to 4.0 liters in the NV van, has been in service for more than 20 years, and is found in nearly every current Infiniti model (all except for the mostly Mercedes-Benz QX30). The most common variant is the 3.7-liter version that makes 330-or-so horsepower, depending on the application. Now, Infiniti has lifted the hood on the VQ’s replacement, the VR. This new, turbocharged V-6, which is making its debut in the 2016 Q50, begins a new chapter in Nissan V-6 engines, and so we’re taking a closer look.
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Godzilla fans will recognize the nomenclature, because the GT-R’s twin-turbo 3.8-liter V-6 goes by the codename VR38DETT. Infiniti says the new VR is in the same family as the GT-R’s VR, but there is enough different about the engine to consider it all new.
-For starters, the new VR isn’t nearly as big. The aluminum block comes in just one size, 3.0 liters, but with multiple outputs, much like the new 911 engines. And unlike the GT-R’s oversquare design, this engine has an identical bore and stroke of 86.0 mm. It is noteworthy that the 86.0-mm-by-86.0-mm cylinder size is rather popular in Japan. Nissan’s SR20 engine, which powered the tuner-friendly Silvia in the Japanese domestic market, and Subaru’s 2.0-liter flat-4 have identically sized cylinders. The Bugatti Veyron’s W-16 also sported 86.0-by-86.0-mm cylinders.
-The new VR comes in either 300- or 400-hp strengths. Both are force-fed air via a pair of turbochargers, and Infiniti says that aside from programming, the only differences between the two versions are their engine mounts and an optical speed sensor for the turbochargers on the 400-hp variant. This speed sensor is what allows engine programmers to spin the VR’s turbos up to 240,000 rpm, a speed Infiniti claims is the fastest of any production V-6 engine.
-Unlike the GT-R’s exhaust-manifold-integrated turbos, the new VR’s turbos bolt directly to the cylinder heads. Incorporating the exhaust manifolds with the head shortens the exhaust’s path to the turbine and reduces weight and size. Infiniti says the engine without the turbos weighs 430 pounds, about 39 pounds less than the VQ it replaces. The turbos and intercoolers add another 57 pounds back onto the total, but the 18-pound net gain is a fair penalty to pay for the added muscle of the turbos. Spray-on bore coatings eliminate the need for iron cylinder liners, saving nearly four pounds.
-Boosted intake air passes through a pair of liquid-to-air intercoolers that are mounted on top of the engine. The idea is to minimize the path from compressor wheel to intake valve, thus improving efficiency and response. The alternative, an air-to-air intercooler, requires lots of plumbing to the front of the car, adding several feet to the distance the air must travel.
-The DOHC heads come packed with 24 valves and cam phasers. Exhaust-valve timing is adjusted with a hydraulic phaser, while the intake valves are adjusted with an electric phaser. Electric phasers are favored for their wider range of variability and quicker reaction time.
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There is still a lot we don’t know about this new engine, such as maximum boost pressure, but we did know that max torque, of 295 or 350 pound-feet, arrives at 1600 rpm and plateaus all the way to 5200 rpm. Whether 300 or 400 horsepower, the power peak is 6400 rpm, and we expect max revs to be about 7000 rpm. We’ll be sure to let you know what we think of the new engine once we get a chance to opens its throttles, early next year.
-from Car and Driver Blog http://blog.caranddriver.com/check-engine-a-deeper-look-at-infinitis-new-twin-turbo-3-0-liter-v-6/
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