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Old 02-10-2013, 11:48 AM   #1
AndrewNance
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Default B20 lightened flywheel - for a DD

How light is too light for a daily driver?
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Old 02-10-2013, 05:21 PM   #2
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Idk for a b20, but my 2.0 Porsche 914 has an 11lbs flywheel in it and drives great, once used to it, I want a lite flywheel for my 142 but don't have cash for that yet, my m41 is on its way out and am gathering parts for a t5 swap (tranny easy part)
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Old 02-10-2013, 05:25 PM   #3
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15 pounds is probably just right. you want just enough energy storage for comfort. remember that the disc and plate is also part of that assembly and net mass.
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Old 02-10-2013, 06:11 PM   #4
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I will take these things into consideration. Thanks guys.
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Old 02-10-2013, 09:08 PM   #5
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I have a 17lb one on mine, love it, could probably go down a couple more pounds but that's it for a daily. sure beats the 24.5lb stock flywheel.
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Old 02-11-2013, 02:42 AM   #6
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~16lb was excellent on my b23. 9-10lb of the aluminum one I have now I feel is too light. the flat b21 flywheel started off at ~20-21lb and was thinned out to around 16lb as I recall.
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Old 02-11-2013, 03:30 AM   #7
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Quote:
Originally Posted by AndrewNance View Post
I will take these things into consideration. Thanks guys.

Does anybody know what the bolt circle is and bolt size?

Steel at around 14 lbs could be done pretty easily when one has blanks and other dimensions set.
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Old 02-11-2013, 12:13 PM   #8
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Depends on what motor he has John. The 8-bolt B20's run the standard B21/23/230 pattern. Not sure on the 6-bolt stuff.
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Old 02-11-2013, 01:05 PM   #9
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Quote:
Originally Posted by gsellstr View Post
Depends on what motor he has John. The 8-bolt B20's run the standard B21/23/230 pattern. Not sure on the 6-bolt stuff.

Yeah that's why I was asking, like is it same bolt, same bolt circle just 6 vs 8?
Same register on the back?
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Old 02-11-2013, 01:12 PM   #10
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We're not much for hard numbers around here, but I suppose I could mosey downstairs with a verynear brake caliper and grab some approximate numbers.

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Old 02-11-2013, 01:13 PM   #11
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It is an 8-bolt flywheel. Probably should have mentioned that in the OP. I have heard a lightened flywheel is a great bang for your buck and a great way to please the butt-dyno with 40 extra faux HP.
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Old 02-11-2013, 01:28 PM   #12
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Quote:
Originally Posted by AndrewNance View Post
It is an 8-bolt flywheel. Probably should have mentioned that in the OP. I have heard a lightened flywheel is a great bang for your buck and a great way to please the butt-dyno with 40 extra faux HP.
Also it depends on what kind of driving you're doing. Lots of stop and go traffic could make a difference in DD quality. When I still had my GSR swapped CRX ( say what you want vtac, and fwd, that thing was fun as hell) I had a very light flywheel in it and it was a bitch in traffic.
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Old 02-11-2013, 01:30 PM   #13
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The guys at the machine shop were comfortable removing 4lbs on the 6bolt flywheel I took them.
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Old 02-11-2013, 01:32 PM   #14
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Quote:
Originally Posted by grnmachine02 View Post
Also it depends on what kind of driving you're doing. Lots of stop and go traffic could make a difference in DD quality. When I still had my GSR swapped CRX ( say what you want vtac, and fwd, that thing was fun as hell) I had a very light flywheel in it and it was a bitch in traffic.
^ This.

I know I'm going to be branded a pariah for saying it, but I like the lighter clutch pedal and heavier dog dish flywheel for what I do with the car.
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Old 02-11-2013, 02:23 PM   #15
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I was dd'ing mine in stop and go rush hour for quite a few years with the lighter flywheel, never bothered me actually. It's actually still able to recover, perhaps a little easier from a near-stall than with the heavier flywheel, still has easily enough grunt to keep things going. I'm actually quite happy with the weight, both for dd'ing and for beating the piss outa it. The shop I took it to had no real concerns with pulling 7.5lbs from it. Only thing is he said never bring another one of those back...he killed 3 cutter bits on it, damn thing was so hard. He's used to American stuff, not old Swedish iron.
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Old 02-11-2013, 02:26 PM   #16
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I might just take it over there and ask them about removing 5 pounds. If they seem sketched out then I'll go from there.
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Old 02-11-2013, 02:59 PM   #17
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Quote:
Originally Posted by gsellstr View Post
I was dd'ing mine in stop and go rush hour for quite a few years with the lighter flywheel, never bothered me actually. It's actually still able to recover, perhaps a little easier from a near-stall than with the heavier flywheel, still has easily enough grunt to keep things going. I'm actually quite happy with the weight, both for dd'ing and for beating the piss outa it. The shop I took it to had no real concerns with pulling 7.5lbs from it. Only thing is he said never bring another one of those back...he killed 3 cutter bits on it, damn thing was so hard. He's used to American stuff, not old Swedish iron.
Those damn things have become half ceramic with all the millions of heat cycles..

And almost nobody is used to machining cast iron anymore....it ain't hi-tech enough.
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Old 02-11-2013, 03:25 PM   #18
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This shop is well versed in iron stuff, hell, even YOU may have heard of em....Rex Hutchinson (been around since before your rally days ).

Not many shops in town that could both lighten AND balance a flywheel. Many could do one or the other, not both, he was able to do both, and that was around 10 years ago.
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Old 02-12-2013, 07:58 AM   #19
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A stock flywheel is about 24 pounds and the consensus on the p1800 group is that 20 pounds is safe.

Here's what Phil Singer has to say about where the material should be removed :

"You need to be conservative for safety reasons, and some shops don't
want to lighten them because of liability concerns. Having a flywheel
come apart is seriously dangerous to your health.

My machinist usually takes off 1/4" depth of the rim on the clutch side,
going about 1/2" in from the ring gear. On the block side, you can taper
the thick outer section somewhat. The overall thickness is unchanged,
other than what's taken off as a normal part of resurfacing. Of course
you need to rebalance it once that's done.

It's only a few pounds lighter, but all the weight comes off the outer
edge where it does the most good."
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Old 02-12-2013, 09:06 AM   #20
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I found putting the TTV flywheel on my 940 turbo actually improved its on road manners. The total mass including the clutch dropped from 24kg (53lbs) to 17kg (37.5lbs) thats 15.5lbs all the stuff people said would happen hasn't. If anything I would like less mass and centre it all better with a 7" clutch and get that weight down even more.
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Old 02-12-2013, 11:30 AM   #21
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I had 6 lbs taken off the stock flat flywheel. No problem...





I've since decided to do the TTV steel piece (they will do either 6 bolt or 8 bolt).




With clutchnet clutch to drive the T5.


I haven't driven the new set-up...car is a little "apart" right now. The TTV is around 11/12 lbs and I don't foresee any issues.
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