I will be installing a JWT clutch setup into my NX over the christmas break, and am wondering about my flywheel options. I realize I wont be in there again for quite a while, so now would be the time to do the flywheel. Basically do i just have it resurfaced? Or I could have it lightened by a shop, take 5 or so pounds off it, but i have heard tht factory lightened flywheels are prone to exploding. Having said that, I know many people on this forum run lightened stock flywheels withiut problems. The I could go all out and spend like 450 bucks on a JUN or CM or JWT lightweight wheel.
So basically what I'm asking are what are your experiences with each? When you lighten a stock flywheel can you actually notice a difference, or should I just spend the (really hard to come by) big bucks and go all out?
TIA

You can get the Fidanza too. It's around $350. I've had it installed for 4,000 miles and have no problems. Really fun mod.

zex/jun ultralight, baby. you'll be glad you did :)

Ric

After I upgrade this week, and fix a few things I may consider a clutch swap. Same JWT, 01SE combo.

I am going to pay maybe 60-80 at most, at a local machine shop to have 3-4 lbs shaved off the stocker. It's strong enough or so I've read ymmv. I'll post back to this thread if, and when I do.

Originally posted by Bennitto Mallito
I am going to pay maybe 60-80 at most, at a local machine shop to have 3-4 lbs shaved off the stocker. It's strong enough or so I've read ymmv.
That'll be just like flushing money down the toilet. I had 5 lbs removed from a 20 lb. stock unit and ran it in my car before the VE swap and noticed absolutely nothing. NOTHING!!!

I've had an 8 lb. Fidanza in the car for nearly 20 track days this season with a pronounced improvement in rev matching and no ill effects.

JGY quit lightening stock ones because their composition is not consistent. I'd go with the Fidanza myself, lightest weight for the money last time I checked.

Wow you pulled your tranny just to put a flywheel? I was jsut gonna do this if I did the clutch. $350 seems like a waste for me, and that's an inexpensive flywheel. I've heard good things about fidanza's.

I see your point though, but 15lb versus 8lb will create a huge inertial difference. I wouldn't expect much difference shaving a stocker anyway.

So you really notice a difference in the revs with a lightweight flywheel? I have my stock flywheel lightened and i don't really feel a difference, i also heard that a flywheel throws off the internal balance, i also want an 8 LB fidanza but if the revs aren't that much noticeable then why not leave the stock ? I just want my engine to rev quick, also would installing underdrive pulleys AND an 8 lb fidanzabe even more efficient? Or would it be better to do either or?

Unless the flywheel was goobered by the machinist, it can't affect internal engine BALANCE. The flywheel has two functions:
provide a friction surface for the clutch
provide inertia for the crankshaft

Item two is what lightened flywheels address. There has to be enough inertia in the reciprocating assembly to make sure the crankshaft makes it far enough around to get the next piston into firing position. More cylinders require less inertia since there are more firing events per revolution.

A four-cylinder engine has a 2 firing events per crankshaft revolution. An eight cylinder (flat or straight) will have 4 so it need less flywheel. A single-cylinder engine will need a heavy-ass flywheel to get the crankshaft around twice before the cylinder fires again.

A side effect of the flywheel inertia is that it softens the impact of the cylinder firing; this is probably what was meant with "throwing off internal balance".

Originally posted by Slartibartfast
Unless the flywheel was goobered by the machinist, it can't affect internal engine BALANCE. The flywheel has two functions:
provide a friction surface for the clutch
provide inertia for the crankshaft

Item two is what lightened flywheels address. There has to be enough inertia in the reciprocating assembly to make sure the crankshaft makes it far enough around to get the next piston into firing position. More cylinders require less inertia since there are more firing events per revolution.

A four-cylinder engine has a 2 firing events per crankshaft revolution. An eight cylinder (flat or straight) will have 4 so it need less flywheel. A single-cylinder engine will need a heavy-ass flywheel to get the crankshaft around twice before the cylinder fires again.

A side effect of the flywheel inertia is that it softens the impact of the cylinder firing; this is probably what was meant with "throwing off internal balance".

I want to know everything this guy knows.

Slartibartfast,
do you have a book out I can buy.
-D

any of you heard of people haveing problems with the jun lightened flywheels? i'm interesting in buying one, and the guys out at sr20development said they've never had any problems, i was wondering if you guy ever had. thanks...adam

~25k trouble free miles so far. you will notice a different "tone" to the sound of your starter engaging the ring gear on it, but that's completely normal.

metro_se-r, I have no single book that I can recommend. I started working on cars right out of high school in 1975. I've had 27 years to gather up car-related knowlege from many sources, primarily car magazines like "Car and Driver" and "Road & Track". All I can say is read, read, read. Especially technical articles like "Suck, Bang, Squish, Blow". I do have an unusual advantage of working with Ph.D. Chemical Engineers so I have access to some specialized reference books and practical knowlege.