An 80-percent-new engine adds six ponies while sipping less fuel.The only exterior change to the 2007 350Z may be subtle—a new hood with a slight center bulge—but there are big changes under that hood. Power is increased to 306 horsepower, a modest six-hp bump for manual-transmission Zs and 19 for automatics, but Nissan claims that 80 percent of the Z’s prolific 3.5-liter VQ engine has been changed. This is the same update—and the same engine—that powers the Infiniti G35 sedan. The changes were extensive enough that Nissan renamed its celebrated V-6 “VQ35HR” (just rolls off the tongue, eh?).
HR stands for "high-revving," reflecting the higher redline for the manual-transmission model, which increases from 7000 rpm to 7500. (The less-fortunate driver of an automatic 350Z can only rev to 6600 rpm, as with the previous engine.)Specifically, the changes to the engine include a higher block deck height, which also results in longer connecting rods, hence the taller hood and a redesigned front strut-tower brace. The VQ35HR also has a new dual-intake system, revised cylinder heads, variable valve timing that operates over a wider range, and a higher compression ratio (10.6:1, up from 10.3:1).
Other highlights are asymmetrical piston skirts and a stiffer cast aluminum engine cover and oil pan.
The benefits are twofold: In addition to the few extra horsepower, the fuel economy is improved by 1 to 2 mpg in EPA city and highway ratings for both manual- and automatic-transmission versions of the coupe and roadster. Engine smoothness is improved as well, and the wider torque band should result in slightly better midrange acceleration.
