RickA

I spoke with a local racing/machine shop today about getting my spare OEM 1.8 flywheel lightened, balanced and resurfaced and was asked a couple questions I was unsure of. He asked if the flywheel is forged or cast and if it can be balanced statically since I don't have a spare crankshaft to mount it on.

patsmx5

iTrader: (16)

I would think it is cast, not forged. I would think the engine is internally balanced, so you would not have to bolt it to the crank to balance it.

Edit: I searched Wiki and Yahoo and can't find a anwer. All I found was the car was a well balanced machine, balanced weight distribution, balanced bla bla bla

neogenesis2004

iTrader: (12)

Its 100% cast, lightening beyond removing the inertia ring on the back is highly UNRECOMMENDED if you enjoy having your legs. It can be balanced separately. Common practice is to balance all components separately and then as a unit.

RickA

The shop I talked to told me the same thing. I told him I only want ~4 lb taken off so he told me it SHOULDN'T take out my legs since it's not a major reduction. When I brought him the flywheel he reassured me that there's plenty of material to take off 4 or 5 lb and still keep my legs.

cjernigan

iTrader: (13)

Pretty sure Ben had this done.

*looking for thread. Found it.
https://www.miataturbo.net/showthrea...=cost+flywheel

neogenesis2004

iTrader: (12)

The ring on the back isn't structural, so removing it is ok. Its only there specifically to add weight.

RickA

So when people talk about a lightened cast flywheel exploding, what part of the flywheel's mass do you remove to make something like that happen?

Yeah I had read that thread previously, but nothing was spoken of manufacturing process or how it can be balanced, both were questions the machine shop here asked me.

cjernigan

iTrader: (13)

Personally, i would buy the ACT steel replacement flywheel. Atleast you know it won't explode. Atleast not as likely.

RickA

Well, I was reassured by the machinist who also builds track cars so i saved myself a few bucks... Flywheel was $45 shipped and the resurface, lighten, and balance was estimated at $100

kylelind

I took the lip off the back and I still have my legs...it did not make a HUGE difference but is noticeable. I just balanced it separately and put it back on...hopefully it is all good.

Ben

iTrader: (33)

Yeah, the machine shop took 5 lbs off of mine to about 14 lbs total. Which was quick and easy for them. It was one of those while you wait type jobs. It was like $100 and I'd recommend it. A good shop should be able to get it down to 12-13 if you wanted them to. Another option is FM's 10 lb flywheel is on sale at $250 right now, brand new.

l_bader

Another option, if your build and budget permits, is to knife-edge the crank instead. You'll still lose rotating mass, but also gain the benefit of reduced drag on internal components.

Ben

iTrader: (33)

Did you nitride your crank after shaving it? If you don't mind, what did that uber-light crank cost?

l_bader

Ben -

No, I didn't think to have it treated after getting it machined. - Hopefully it won't turn out to be a mistake.

Profiling, lightening and knife-edging the crank and then balancing the crank, flywheel and pressure plate individually and as a single unit was a touch over $800.

Total cost on all the machine work done on the block before taking up to Corky's was about $1700.

- L