NISMO had it easy with the Spec V. In stock form, the fastest of the Sentras is far from its potential and NISMO, as we saw in last month’s test, can work wonders with that scenario. Things aren’t so easy in the land of Z. The 350Z, though certainly not at the limit of its chassis’ capabilities, leaves relatively little on the table in stock form.
Both the S-Tune (the silver one) and R-Tune (the blue one) cars we tested have NISMO’s 304-stainless-steel cat-back exhaust. The stock exhaust’s bottleneck is the Y-pipe that merges the flow from the two cylinder banks. The NISMO system, then, has to replace this part to get any gains. Before the Y, NISMO uses 2.4-inch tubing, afterward it’s 3-inch. In total, the system weighs 9 pounds less than the stock one, but makes only about 4 hp in our dyno tests. (We had a stock Track Package Z along for all our testing so weather conditions wouldn’t skew the results.) The exhaust sound, not surprisingly, is beautiful. The VQ35 is probably the sweetest-sounding V6 to come out of Japan—a huge improvement over the flatulent VG30—and NISMO’s exhaust lets you hear it just that much better when you play with the throttle. At idle or light cruise, though, it’s hardly louder than stock.
That’s the extent of power mods for the S-Tune level (parts that are emissions legal and covered under a three-year, 36,000-mile warranty if they’re installed by a Nissan dealer), but R-Tune starts looking quite good from here on out. At least on paper. The cramped exhaust manifolds are replaced with tubular headers crafted, again, from 304 stainless steel. The headers feature stepped primaries that grow from 1.625 inches to 1.750 inches before merging in 2.25-inch collectors. Next, the R-Tune gets a mild set of cams. Valve lift is increased from 0.376 inches to 0.426 inches and duration steps up from 240 degrees to 262. The cams offer little downside, thanks to the Z’s variable intake cam timing. With the system automatically dialing out valve overlap at idle and low rpm, there’s none of the lopey idle you might secretly wish for. Instead, there’s just a subtle occasional misfire at idle and the same responsive, torquey bottom end the engine already had.
The cams do hide one dirty little secret, though. Labor costs. Installation is, at best, an eight- to 10-hour job. It’s a similar story with the headers, which typically take five to six hours to install. Start counting parts (four cams, two headers) and labor hours, and you start to understand the appeal of the inline four.
The crowning underhood jewel, at least acoustically, is the cold-air intake. Now, to be perfectly fair, the stock intake is also a cold-air intake, taking its air from ahead of the radiator. The aluminum NISMO piece adds some healthy acoustic resonance tuning, and with that comes a howl that’s easily the car’s most rewarding aspect. Romp on the throttle and the combined sound from the intake and exhaust is soul stirring. Do it in a tunnel and you won’t be able to stand up for an hour.
Nissan R-Tune adds a clever, adjustable clutch-type limited slip. The NISMO limited slip can be set up as a two-way (works under acceleration and engine braking) or 1.5-way (same thing, but it’s not as strong under engine braking). We recommend 1.5-way. The pre-load on the clutch packs is also adjustable by removing the right-hand stub axle and stuffing a 19mm socket in the hole. The three settings give a breakaway torque of 50, 69, or 101 lb-ft.
If you disassemble the differential, of course, you could also lower the breakaway torque even more by re-arranging the 10 clutch plates on each side of the diff so that some of them are inactive. NISMO doesn’t officially state this, but it doesn’t have to, that’s just how clutch-type diffs work. The NISMO diff is also stronger than the stock one, since it transmits torque through four pinion gears instead of the stock diff’s two.
We don’t know how the diff in our car was set up, but whatever it was, it was too tight for the street. On the track, where you brake, turn, and accelerate through every corner in the same smooth, predictable fashion, a tight limited slip can be good. Drive a narrow, twisty mountain road at night, though, and you won’t be laying into the gas at the apex and holding it down all the way to the next corner. Not with 249 hp at the wheels. Instead, you tend to feed in and out of the gas as you try to stay between the yellow line and the white one and figure out when this damn corner is going to end.
Rolling on and off the throttle like this makes the rear wheels lock together and release every time, which makes the front tires push and then grab with every move of your right foot. That makes you look like a swervy monkey. Don’t believe us? Look at the skidpad results. The S-Tune car, which uses the loose factory limited slip, pulled an impressive 0.98g. The R-Tune Z, with exactly the same suspension, but the NISMO diff, pulled "only" 0.95.