Testing JWT’s Nissan 370Z Ultra Light Flywheel

Testing JWT's Nissan 370Z Ultra Light Flywheel and Heavy Duty Clutch

By Mike Kojima

Most of us are familiar with the advantages of a light flywheel. A light flywheel robs less power from the engine, as an engine accelerates through its rev range; a flywheel’s mass requires power to accelerate it to higher rpm. A lighter flywheel frees up the engines power that would be spent spooling up the heavy flywheel, so although a flywheel doesn’t actually make more power, it allows more power to reach the wheels. A light flywheel also allows the revs of the input shaft to fall slightly quicker during shifts, unloading it, making work for the transmission’s synchronizers a little easier, speeding shifting and extending syncro life.

A light flywheel does have some disadvantages. Generally a lighter flywheel needs a little more clutch slippage to get off the line smoothly. A lighter flywheel also transmits more of the engines vibrations through the drivetrain where they can become annoying to the driver and passengers. On the Nissan 370Z a lighter flywheel can also increases input shaft rattle, a rattling noise present at low rpm. There is also the question of compatibility between the flywheel and the 370Z 6-speed sports model’s high tech computer controlled SynchroRev system

Technosquare's Howard and Ritchie Watanabe had the 370Z's tranmission out of the car in no time

From a performance standpoint, the Nissan 370Z probably is one of the best candidates for performance improvement from a flywheel because of its extremely heavy stock clutch and flywheel. The stock flywheel weighs a stout 32 lbs, the pressure plate 16 lbs and the clutch disc 3 lbs. That’s 51 lbs of rotating weight that must be spun to speed at the end of the crankshaft! Why is the stock 370Z’s flywheel so weighty? In an effort to reduce NVH (That’s engineers speak for Noise Vibration and Harshness) to extremely low levels, Nissan made the stock flywheel very heavy. The heaviness of the flywheel helps to smooth out power impulses of the VQ37VHR engine. This makes the engine feel smoother, like a V8 and also reduces the pulses that create the harmonic that can cause transmission input shaft rattle.

The crank face must be spotlessly clean.  The flywheel must be square on the cranks register and the bolts torqued and tightened twice, the second time with loctite to avoid problems.  A hydraulic throwout bearing is a really cool feature.  It is quieter in operation and lasts much longer as the bearing is always in contact with the diaphragm spring. Although this system was somewhat problematic in early 350Z's it was countermeasured in 2008.  We weighed all the parts on an electronic scale

To further damp out vibrations the 370Z’s flywheel is what’s called a dual mass flywheel. First introduced on the VQ35DE engine found in the 350Z, the flywheel is a two piece affair; one part is attached to the crank and the other half which contacts the clutch disc, has most of its mass on the rim. This side of the flywheel floats freely from the crank on a sleeve bearing, constrained by springs. The free floating part of the flywheel is designed to act as a mass damper and is tuned to damp out low rpm vibrations. This technology is usually reserved to smooth out the strong power impulses of diesel engines but Nissan is using this on the VQ37VHR.

At 16 lbs the JWT flywheel is half the weight of the stock unit.  The stock unit is heavy because of its steel construction and unique dual mass technology that acts like a vibration damper