Shave the stock flywheel or leave it alone? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-16-2008, 03:04 PM   #1
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Default Shave the stock flywheel or leave it alone?

I believe turbo cars generally benefit from a heavier flywheel (relative to an na engine) but I think 20lbs is retarded heavy and since I'm doing the clutch and need to resurface it should I also get it shaved a few pounds?

Will it even make a noticeable difference if its only 3-5lbs? Or is it just a waste of money?
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Old 03-16-2008, 03:32 PM   #2
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You can't just grind off a substantial amount of material from the surface of the flywheel. It has a minimum safe thickness. I think those who have removed weight from an OEM flywheel have done so by profiling the back side. You'd be better served if you were to purchase a lightweight flywheel from the start instead of having the OEM flywheel lightened. Probably save money in the long run, and the aftermarket lightweight flywheel is still going to be lighter.
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Old 03-16-2008, 03:39 PM   #3
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Cost me and my girlfriend about $170 to shave the ring down on her 1.6 Flywheel.

We replaced the clutch with an exedy stock replacement that only had a couple hundred miles (cheaper than buying a new one, got it for free) so we had the flywheel machined while it was all apart. Three day turn-around at a local machine shop, $170, and it was about 7-8 lbs. lighter.

Noticeable improvement on accel, and it's not super-stupid light.

-meaty
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Old 03-16-2008, 04:08 PM   #4
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Quote:
Originally Posted by soflarick View Post
You can't just grind off a substantial amount of material from the surface of the flywheel. It has a minimum safe thickness. I think those who have removed weight from an OEM flywheel have done so by profiling the back side. You'd be better served if you were to purchase a lightweight flywheel from the start instead of having the OEM flywheel lightened. Probably save money in the long run, and the aftermarket lightweight flywheel is still going to be lighter.
A few have gotten their oem's shaved and if it costs me 50bux then its way cheaper than 250-300 plus shipping for a new lightweight one..
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Old 03-16-2008, 04:21 PM   #5
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dc2696 the best thing to do is to drive a miata with a lightweight flywheel first,just to see if you will like the way the car behaves before you spend the money on getting it machined.
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Old 03-16-2008, 04:36 PM   #6
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Quote:
Originally Posted by spike View Post
dc2696 the best thing to do is to drive a miata with a lightweight flywheel first,just to see if you will like the way the car behaves before you spend the money on getting it machined.
That would be ideal but since it just snowed 4inches over the last two nights and I have only this week to get it done (first race is april 20) I dont think I can do that.

Either way I'm sure I can deal with the driveability characteristics, I'm more concerned about the trade offs with the turbo and the effects the flywheel will have on boosting.

I am under the impression that lighting the flywheel will negatively effect boost response, something about less load but I'm sure the benefits of lighting will outweigh the boost issue.
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Old 03-16-2008, 05:15 PM   #7
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I say shave it. I spent $40 to shave the ring off the back of my flywheel and dropped almost 5 lbs, and IIRC I ended up with a flywheel that weighed around 12lbs. The ring on the back of the flywheel is toward the outside of the flywheel so it's exactly where you want weight removed.

So what you end up with is a lighter flywheel that helps with rev matching/etc... without the buzzing/drivability/cost of an aluminum one. Granted it doesn't make as big a difference FI compared to NA, but still worth $40-50 IMHO.
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Old 03-16-2008, 05:28 PM   #8
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Quote:
Originally Posted by brgracer View Post
So what you end up with is a lighter flywheel that helps with rev matching/etc... without the buzzing/drivability/cost of an aluminum one. Granted it doesn't make as big a difference FI compared to NA, but still worth $40-50 IMHO.
+1 shave it
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Old 03-16-2008, 11:34 PM   #9
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I say do the job once and get the lightweight one. I did and couldn't be happier. Heel toe is a easy as ever now and revs freely now.

Don't get chromoly steel. Heard bad things, like really loud whining and bad vibrations. Best off with Fidanza or ACT.
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Old 03-16-2008, 11:39 PM   #10
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I would just shave the stock one. It seems more cost effective and it doesn't have any compromises to extended use or make it less drivable. Plus like you already stated, for turbo you want the flywheel to maintain some inertia and not fall out of boost quicker.
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Old 03-16-2008, 11:43 PM   #11
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just shave it..... i spent 400 on a lightened spec flywheel on my 240sx for the sr20 swap, I loved it to death but 400!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!! way too much to spend for better throttle response IMO
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Old 03-16-2008, 11:51 PM   #12
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240...opposed to people spending $1800ish on IRTB's
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Old 03-16-2008, 11:59 PM   #13
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thats why i might do a DIY gsxr IRTB setup this summer if im bored.. lol im too broke for a turbo right now.

If you have the money, and have purchased a nice clutch... go for it, but on the DIY cheap side... shave it
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Old 03-17-2008, 12:01 AM   #14
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Originally Posted by 240_to_miata_OWNER View Post
thats why i might do a DIY gsxr IRTB setup this summer if im bored.. lol im too broke for a turbo right now.

If you have the money, and have purchased a nice clutch... go for it, but on the DIY cheap side... shave it

Then you could always make an intake plenum for the IRTB and add boost in the future like I want to do.
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Old 03-17-2008, 12:02 AM   #15
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yeah im planning on keeping the IRTB for boost..... if i do them
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Old 03-17-2008, 12:24 AM   #16
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I've got a ~8lb flywheel in the car and I can't even tell its there anymore. Could when I first put it in, but after a couple months driving it I don't really notice it anymore.

If I have to replace my clutch I'm selling it and going with a stock 1.8 flywheel.

Gary from the Miata club had his 1.8 flywheel done, get in touch with him and see what his experience was.
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Old 03-17-2008, 11:46 AM   #17
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If it's as inexpensive as you guys say about shaving off the weight from the back of the OEM flywheel, then go ahead and do it. I assume that price includes resurfacing the friction surface. $400 for a Fidanza flywheel, you were ripped off unless it was a recent purchase, then I think the falling dollar had a hand in the price. I paid less than $300 for mine about 1.5 years ago. BTW, I don't seem to have a problem with driveability on my car that has a Fidanza 1.8l flywheel and SPEC aluminum clutch. It has excellent street manners.
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Old 03-17-2008, 01:10 PM   #18
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shave the bitch...nothing to crazt, but i agree with you 20lbs is a bit too much, id like mine anywhere from 12-15lbs...id be happy with that
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Old 03-17-2008, 01:24 PM   #19
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Shave it. I've got like $120 or something in mine to lighten, balance and surface mine. Which was on the high side, but it was money well spent.
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Old 03-17-2008, 05:14 PM   #20
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Well then its decided, I think I can shave the weight at work on the lathe but I'll see how much the machine shop charges first. Thanks for the help guys.
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