Part review: JUN 4.6kg Lightweight Flywheel B6

http://i.imgur.com/jUPlhef.jpg

JUN AUTO - Lightweight Flywheel for B6-ZE

Part#: 2001M-Z001

Weight: 4.6 kg / 10.14 lbs (std: 8.0 kg / 17.63 lbs)
Material: forged chrome-molybdenum steel

Website: http://www.junauto.co.jp/products/fl.../index.en.html

Driving impression after 8k kms / 5k miles

This review will cover the Jun flywheel but most of it would apply to any lightweight flywheel regardless of brand.

• Acceleration response is slightly increased, accentuating the revvy nature of the B6 engine.
• The more noticeable difference can be felt in the deceleration as the flywheel makes great use of engine braking.
• On the street this results in sometimes finding yourself in the correct gear but losing speed down a hill.
• Rev matching/heel-n-toe become noticeably easier to execute.
• Taking your foot completely off the gas suddenly will cause the car to jerk rather violently as it decelerates rapidly. You will learn to drive smoother with finer inputs to avoid this.
• When all conditions outside and inside are quiet you can hear the engine sing a new song as the flywheel rotates. You may or may not like it:)
• The lighter the flywheel the less street friendly it will be (consider the factors above).
• Maruha recommend a 5.0kg one. I would also recommend anything between 5.0kg - 5.5kg (11lbs - 12lbs), and not less than 4.5kg (10lbs) unless it is a race car.

Recommendation:
Only if you love revving, and you love NA, and you are taking out your gearbox/clutch anyway. If you have a B6 and 4.3 gear ratio, this should tempt you even more (buy any reputable brand).

Reference video: Revving in neutral std 8.0kg flywheel vs 5.0kg one
https://www.youtube.com/watch?v=eaJNx7yWmk4

Good review! a lightweight flywheel is next on my list of things to buy.

Thanks for the review! :bow:

I just picked up a used(approx. 2k miles) Flyin Miata 10.3lb flywheel and i can't wait to get in with my Spec Stage III clutch! A good (which means decently stiff, imho) clutch and lighter flywheel REALLY makes the driving experience so much better. I finally drove a miata with a aftermarket clutch and lightweight flywheel, thanks to MC70, and really enjoyed it.

The only previous experience i had was with a '01 Bullitt and at first was alarmed by the drivetrain noise it amplifies, especially in cold weather, but after lots of reading about the nature of lightweight flywheels it didn't bother me and i enjoyed thoroughly!

For those unfamiliar with lightweight flywheels the best analogy i read was it comparing the flywheel to a music triangle: a smaller/thinner one will create a higher pitch tone and resonate longer vs a heavier/thicker one creates a deeper tone and resonance dissipates quicker, the same with a flywheel. The heavier ones do not transfer the drivetrain noise like the lighter ones and of course the lighter they are the more pronounced drivetrain noise is.

You might have sold me....

I love that whine, one of the reasons (aside from better feel) that I love poly differential bushings.