Nissan’s VQ V-6 Engine Makes a Comeback

The respected VQ-series V-6 powers a variety of Nissan and Infiniti-brand cars, CUVs, trucks and SUVs, and it has been a favorite of WardsAuto editors for two decades. In displacements ranging from 3.0L to 3.7L, it made the Wards 10 Best Engines list 14 years straight from 1995 to 2008.

But it’s hard to keep up that pace forever when all-new powertrains are being introduced by competitors at unprecedented rates. Eventually the VQ became a bit less competitive in fuel efficiency and in some applications lost refinement as displacement and output increased. But now it’s back after an 8-year hiatus for a 15th Wards 10 Best Engines award.

Kentaro Watanabe, senior manager-Powertrain Engineering at Nissan Technical Center North America, says the primary design objectives for this nearly 2/3-new VQ V-6 were: “Improve engine efficiency for better vehicle fuel economy; meet stringent emissions regulations of LEV3-ULEV125 as well as MSAT (mobile source air toxic emissions); maintain previous-model engine NVH and achieve 300 horsepower without compromising any of the above.” All of which the VQ engine team have more than accomplished.

There is no question the new VQ’s NVH is better in the ’16 Maxima than the same-size 290-hp outgoing VQ V-6 was in the ’15 version. And its fuel efficiency is well up from the previous 19/26 mpg (12.4-9.0 L/100 km) city/highway.

“It’s quiet and smooth, with just enough grunt,” says editor Dave Zoia. “VQ is back!”

And while most other automakers are phasing out V-6s in favor of smaller, lighter and typically more fuel-thrifty turbocharged 4-cyl. engines in their midsize, and some larger, cars and CUVs, this much-improved DOHC, 24-valve, all-aluminum 3.5L V-6 is the only engine offered in the ’16 Maxima, which Nissan bills as a “large” sedan. And it’s not even (yet) direct-fuel-injected, making do instead with less complex and less expensive port fuel injection.

VQs powering the new Pathfinder and Armada trucks do feature Nissan's new direct-injection system.

Nevertheless, it spins out a healthy 300 horsepower at 6,400 rpm (that’s 85.7 hp/L specific output) and a strong 261 lb.-ft. (354 Nm) of torque at 4,400 rpm while scoring very respectable 22/30 mpg (10.7-7.8 L/100 km) city/highway fuel-economy ratings from the EPA. During their driving and testing, WardsAuto editors “routinely” topped 25 mpg (9.4 L/100 km), and some saw as much as 30 mpg in real-world driving.    

To refresh readers’ memories, here is what the judges wrote about the award-winning 3.7L VQ back in 2008, its last Wards 10 Best honor until now: “When Nissan engineers kicked off design of an all-new V-6 engine family 18 (now 26) years ago, they planned to make it at least the equal of any, and better than most. They could not have predicted how powerful, popular and prolific it would be nearly two decades later.

“GM has its legendary small-block V-8, BMW its silky in-line six, VW/Audi their mighty-mite turbo four. Now Nissan has its signature VQ V-6 powering nearly everything it makes midsize and up,” we wrote. “Together with bold, distinctive styling, it also arguably powered the company’s comeback from the brink of bankruptcy earlier this century, at least in the U.S. market.”

The first all-aluminum VQ V-6 debuted in 1994 in 2.0L, 2.5L and 3.0L displacements, the latter bringing 190 horses and 205 lb.-ft. (278 Nm) of torque to new U.S.-market ’95 Nissan Maxima and Infiniti i30 sedans. It was relatively light and compact, with lightweight internal parts, micro-finished camshafts and crankshaft, molybdenum-coated pistons and a 2-way cooling system that enables the block to warm up more quickly for reduced emissions.

61% New Parts  

Today, the thoroughly upgraded VQ35, which comes standard in the all-new ’16 Maxima sport sedan, is 61% new, according to Nissan. Up top, its redesigned intake manifold (with wider and shorter runners), heads and combustion chambers give it significantly better flow for higher output. At its bottom end, a much stiffer new oil pan reduces vibration. In between, it boasts reduced friction throughout, “intermediate locking valve timing” for more complete combustion and sodium-filled exhaust valves (from Eaton) that conduct heat away from its combustion chambers.

“The improved VQ makes for light, lively and refined power delivery through an ideally suited continuously variable transmission. We barely miss the shift points,” writes editor Tom Murphy. “For more than 20 years, the VQ’s calling card has been its unmistakably creamy midrange. But the new version displays a lot more composure when pushed hard, even to the brink of the 6,600-rpm redline.” He sums it up as, “a modern, silky smooth V-6 that can pull extra duty in luxury cars, sport sedans, CUVs and even pickup trucks.”

Nissan’s Watanabe adds that the engine team’s toughest challenge was reaching that customer-pleasing performance/efficiency balance along with the improved NVH levels. Another difficult challenge, he says, was optimizing the cylinder head port shape for higher tumble flow with less flow restriction, and the engineers made extensive use of computational fluid dynamics to accomplish that. Also proving challenging was precision-tuning both the spark and the valve timing and stiffening up the oil pan to suppress the additional engine vibrations that resulted from rapid combustion due to the high tumble ratio.

Did any key engineering innovations help the team achieve its goals? Yes, he says and among the most important are “a highly optimized short intake manifold and long exhaust system, a larger-event-angle exhaust cam phaser and a low-flow-restriction exhaust catalyst,” in addition to the vibration-fighting oil pan.

Among this new VQ’s key suppliers are Mann + Hummel for the intake manifold, Arvin Sango and Calsonic Kansei for the exhaust system, Hitachi for the cam phasor, Bocar for the oil pan and Nemak for the cylinder head casting.

As smooth, powerful and efficient as WardsAuto editors deemed this renewed 3.5LV-6 to be in their ’16 Maxima test car, Watanabe says there remains room for improvement in future generations in both output and energy efficiency. In addition to further friction reductions and combustion system improvements, expansion of gasoline direct injection is likely to be at the top of the list, along with the higher compression ratios GDI will enable.