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Lightweight Flywheel
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Mavfan  



Joined: 01 Oct 2004
Posts: 113
Location: St. Louis, MO

PostPosted: Tue May 03, 2005 2:30 am    Post subject: Lightweight Flywheel Reply with quote

Do you guys recommend upgrading to a lightweight flywheel on a 88 924s?
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ideola  



Joined: 01 Oct 2004
Posts: 15505
Location: Woodstock IL

PostPosted: Tue May 03, 2005 4:06 am    Post subject: Reply with quote

Depends...do you want low end torque or high end RPMs?
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Helstrm  



Joined: 05 Feb 2005
Posts: 198
Location: Columbia, SC

PostPosted: Tue May 03, 2005 9:21 am    Post subject: Reply with quote

This is a good question. Is there a middle of the road place I can find..

I have a lathe and just made a rig to mount the fly wheel on. I have seen people take 7lbs off. Wondered what would happen if I pulled 3 lbs off...
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Mavfan  



Joined: 01 Oct 2004
Posts: 113
Location: St. Louis, MO

PostPosted: Tue May 03, 2005 11:00 am    Post subject: Reply with quote

well the car has low end torque, but no high end, this is what i want since if you're going to be racing, it will only be in the high rpm's.
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Lizard  



Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada

PostPosted: Tue May 03, 2005 11:40 am    Post subject: Reply with quote

adding a lightened flywheel will not give you more top end, it will simply decrease the time it takes for the engine to rev up as there is less rotational mass.
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Helstrm  



Joined: 05 Feb 2005
Posts: 198
Location: Columbia, SC

PostPosted: Tue May 03, 2005 1:21 pm    Post subject: Reply with quote

So how much can I remove without having the car stall when I come to a stop... With the US speed limits I can't use more top end anyway.
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ESC944  



Joined: 21 May 2004
Posts: 747
Location: FL

PostPosted: Tue May 03, 2005 1:29 pm    Post subject: Reply with quote

Well typicall for a 944 flywheel when lightened is going down from 17 lbs to 9 lbs so thats a loss of 8 lbs. I imagine the 924 would see something similar.

I know a few places that do this, not to expensive, you should be able to find a good performance/hot rod machine shop that could do the job.
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Lizard  



Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada

PostPosted: Tue May 03, 2005 2:02 pm    Post subject: Reply with quote

ona fuel injection car, a full aluminum flywheel will not cause it to stall if it is running properly, if it does stall then you have other issues,
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Joes924Racer  



Joined: 03 Nov 2002
Posts: 11964
Location: Oregon, Denver Colorado native!

PostPosted: Tue May 03, 2005 4:22 pm    Post subject: Reply with quote

I have a shop here thatll do it for about 65.00
tops ..ited be nice to do..thats one mod I even though
I got 3 extra fly whls I havent had the work done yet.
Guess Im saving it fior that high cp p&p headered &
camed version.
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Helstrm  



Joined: 05 Feb 2005
Posts: 198
Location: Columbia, SC

PostPosted: Tue May 03, 2005 10:58 pm    Post subject: Reply with quote

Since we made our own tool for this rig it won't cost a dime to cut the wheel down.



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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Wed May 04, 2005 12:42 am    Post subject: Reply with quote

Doesn't reducing rotational mass really impact your low end torque? Isn't it low end torque that launches the car off the line? I'm not sure I would want to lose anymore torque, as the NAs just don't move that quick. I could understand it for a racing application, but not for street.
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Helstrm  



Joined: 05 Feb 2005
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Location: Columbia, SC

PostPosted: Wed May 04, 2005 1:24 am    Post subject: Reply with quote

I may be wrong but I doubt you would lose anything. Just rev up faster. But I am not sure.
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ideola  



Joined: 01 Oct 2004
Posts: 15505
Location: Woodstock IL

PostPosted: Wed May 04, 2005 1:41 am    Post subject: Reply with quote

Hmmm....what I've read and heard indicates that the higher the rotational mass, the more torque. Hence, reduction in the mass of the crank (through knife-edging or other such mods) and the flywheel will reduce the low-end torque.

The theory as it's been explained to me is that it's a trade-off. If you're looking for off-the-line launches (e.g. drag racing) or quick acceleration coming out of hard cornering (e.g. autocross), you need torque, therefore you would want to preserve some rotational mass. For balls-out high speed racing with not a lot of hard cornering, quick revving to get high-end HP would benefit from lower rotational mass.

Or maybe I don't understand this stuff at all...I don't have practical experience, so I'm no expert by any stretch! I'm just repeating what I've been told based on my own investigations into lightweight flywheels and cranks.
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Smoothie  



Joined: 01 Jan 2003
Posts: 8030
Location: DE (the one near MD, PA, NJ)

PostPosted: Wed May 04, 2005 2:43 am    Post subject: Reply with quote

Yes, more flywheel weight = more torque. The flywheel in motion is stored energy - once it's spinning, it's gonna want to keep spinning and the heavier it is, the more energy it would take to make it stop. Horsepower is consumed in getting the flywheel up to speed, and that's horsepower that's diverted from contributing immediately to the cars' accelleration, but that energy used, becomes stored energy, stored as flywheel inertia and available as torque. A heavier flywheel also makes the engine run smoother.
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Helstrm  



Joined: 05 Feb 2005
Posts: 198
Location: Columbia, SC

PostPosted: Wed May 04, 2005 2:52 am    Post subject: Reply with quote

Cool. Then I will leave the flywheel as is and just resurface it.. Thanks.
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