2007 Nissan 350Z

     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.