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SHAVING THE FLYWHEEL


allen_hammond

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A seriously lightened original is 15#, plus 24# for the cover. That's (just call it) 40#. It's not SFI rated, and I wouldn't use it over the stock rpm range of the vehicle.

 

For the cost of an 11# Tilton, the SFI rating, billet construction gives me peace of mind with little/no performance difference. If I was RACING on a road course, Tilton or any of the other aftermarket items. Generally the lighter the better. The 4.5Kg units are even lighter than the Tilton, but all still use the 24# stock clutch cover. so at BEST you are only going to get around 32-33# on a standard diameter conventional flywheel.

 

That is 2X the weight of the 10,000 rpm unit out of Lancaster, the Tilton Triple-Plate, or any of the Quartermaster units.

 

TWO TIMES THE WEIGHT---that is the kind of step you have...

 

If it's a dual purpose car, you CAN get a low-inertia double or triple plate Quartermaster unit with an inertia ring...but you kind of defeat the purpose (especially if you have the torque that needs the double disc!) I have not had an issue driving my car with an HKS 9# flywheel, but I don't drag race it. It does take some getting used to, and it's not for everybody. But for a dual-purpose car I would say that would be the best you could do. The low inertia triple disc stuff is just too light for a smooth launch and you will burn it up in short order causing $300 rebuild to be due.

 

The big difference people miss is that pressure plate. It's 24# no matter what, so they see flywheel weight and forget that they have to add 24# to it (basically doubling the weight of the early 240 flywheel!) The jump to dedicated modular units removes this weight, AND gives a significantly reduced moment of inertia making them unsuitable for the street. It's not the weight, as I said early on, it's where the weight is removed from! a 15# modular is a neck-snapper compared to the Centerforce 15# aluminum unit (which in reality is 39#!!!)

 

Follow? Basically once you get to the CrMo 4.2Kg units, that's the lower limit. The next step is to go modular at half the weight. You can get that inertia ring on a modular unit, but do you really want a $1000 clutch to save 7# when you can get the CrMo for $240 and use STANDARD clutch components and basically replace them at standard intervals because they don't burn up every stop-n-go session?

Edited by Tony D
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Yeah I didn't consider the fact that the lightened wheel will still have to use the old bulky pressure plate...

 

So in terms of lowest (reasonable) *total* weight, a lightened wheel will still be too heavy/possibly unsafe, but a completely modular unit that weighs even less than the original wheel altogether is overkill for street use because it would just be too sensitive to be fun. In the middle ground, going one direction and getting a light multi-plate clutch would offset the weight of a heavier wheel, but isn't really worth the hassle/money, sooo, the ideal option is to get a super light billet wheel to offset the heavy standard clutch because it will be about the same as the former's total weight plus sustainability.

 

Is that the gist of it?

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If you can use a clutch and aren't using a grabby double-metallic clutch, it will leave smoothly and drive fine.

 

My kid learned on a 3.3L Frontier. He adapted to a 15# centerforce flywheel very quickly. Still a little jerky because I don't let him drive it all that often...

 

I don't think any of those are overly light...the superlight 9# Flywheels will likely be tedious for people lazy with their feet. If you have torque and a low rear end, you better be very smooth with your right foot and coordinated with your left.

 

The Tilton and Centerforce should easily be smoothly controllable by any beginner driver if they have any sense of throttle modulation and know what gear to be in at what speed!

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Truthfully, the way your throttle tip-in is modulated makes for a big difference in the 'snap' you feel with a big-torque engine. I put a progressive cam on my triple ITB's and the modulation of the cars engagement and in-gear snap when idling along was quite a bit better.

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  • 1 year later...

Yeah im bringing this one back up from the dead...

 

So im building up a turbo motor shooting for 350 whp and this car will mainly be driven on the street and will see occasional 1/4 fun :0 and possibly some autocross if i get around to doing some brake upgrades.

 

I am going to be using a hybrid clutch from south bend clutch its a stage 2 240mm using the 350z pressure plate and organic on one side of the disc and feramic on the flywheel side.

 

I bought a stock flywheel would it be worth the money to have it lightened to 17 lbs or so or should i not worry about it and just leave it the stock weight?

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  • 2 weeks later...

I have a lightened stocker in the floor next to me...chucked it up on the lathe and cut it down to 18lbs...225mm flywheel. Was dissapointed in the weight reduction, but it's as thin as I'd feel comfortable with. I'll end up buying a CrMo unit eventually.

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I went with a lightened Fidanza unit in my 280zx NA. Pretty stock car, and it doens't hinder driving at all, the car is my daily.

 

I like to think it's one of those parts you only want to install once in a lifetime (depending how you drive) and from the above two responses +mine I would definitely install a lightened unit.

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  • 8 months later...

Did I mention the 9# unit I have is in a turbo car?

 

Answer your question?

 

If you're gonna drag race, a light flywheel isn't really what you want... And the inertia of a heavier flywheel can shear the clutch disc stop rivets, making the damping springs come out...or launch something!

 

JeffP went to.McLeod for a clutch disc due to the shearing issue using the Fidanza on his 600+HP car

Edited by Tony D
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Truthfully, the way your throttle tip-in is modulated makes for a big difference in the 'snap' you feel with a big-torque engine. I put a progressive cam on my triple ITB's and the modulation of the cars engagement and in-gear snap when idling along was quite a bit better.

 

Tony, can you provide more details on the 'progressive cam' you mentioned?  When I hear progressive cam I start thinking VTEC and I didn't really think that was an option for the L6. 

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Allen you want to further lighten the flywheel you got from me? . On my car now I use a JWT one and is working out great. On the previous one I had lightened I got a core close to the shop that did the machine work and that saved me shipping cost. I would really recommend you have it done by a shop who has experience and its needs to be balanced and they need to know where to shave the weight

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