Do i need to spend 300+ on a flywheel?

Hey all!

Im looking for advice on a lightened flywheel for a 94 1.8 miata.  

i bought a SuperMiata clutch with the organic disc, figuring on using my stock flywheel.  On hindsight, i'm thinking this isn't the best idea, since i'm in there anyway. I'm removing the flywheel anyway to install a new rear main seal, so might as well upgrade.

The big rub to this is brand name flywheels are almost the same cost as a full clutch kit, including pilot and throwout bearings. it's a hunk of metal with a ring gear, know what I mean?

Has anyone used an off-brand flywheel and not worried about their foot being cut off in an incident?  

This isn't an endurance racer, but does get driven hard on track days with occasional street driving   

I was looking at an "ebay" XTD lightened flywheel.  is there anything to worry about, or should i just buck up and by the supermiata flywheel or buy the slightly cheaper ACT flywheel?

i have only heard of incident is drag racing, and i have no interest in that, however, the car will be turboed shortly and looking for 220-250 hp.  

Thank you for you time and thoughts on this. 

In reply to d_jabsd :

What's your foot worth to you?

I'm friends with a guy running a do miata who runs a stock flywheel. If it needs surfaced, have it surfaced, but that's not a place for cheap ebay parts in my book.

In reply to Apexcarver :

Agreed, My foot is worth a ton, however, it doesn't seem to happen at all outside of high-horsepower drag racing, where scatter shields are pretty much a requirement. It seems to me to be an opportunity cost for the manufacturers, but i don't know.  that's why i'm asking.  

Is it just insurance, or does it really happen?  With number of lemons an 20XX racers on here, i figure this is the best place to ask.  

Maybe get the cheap one and get it balanced by a machine shop? I've fought with this one before, but didn't do anything about it.... put the stock one right back in.

d_jabsd said:

it's a hunk of metal with a ring gear, know what I mean?

 

If it's that simple, just make your own.

If the cheapo unit shakes, you'll have to go back in to put the good one in anyway. If it comes apart, it will cause more than the cost of the flywheel in damage.

Cheap chineseium parts go where they're easily replaced or won't cause too much collateral damage.

Centrifugal force operates on an exponential scale, not a linear one. There's a lot of force on a flywheel at 5000 rpm.

Boss9 on a dyno with a cast iron flywheel: https://youtu.be/FOnachbSjno

In reply to ShawnG :

Honda flywheels used to be ( and maybe still are ) made locally. Their equipment looked designed to crank them out quickly but not particularly accurate.   In the 1970's I had my Jaguar flywheel lightened past the danger point. The machinist was shaking his head no-no-no  and made me sign a waver. Never had a lick of a problem until the Riverside nationals when I'd lost my brakes and was using the gearbox to slow down a 2750 pound race car, racing the Factory Jenson Healey.  One lap to go and up at turn 6 it shattered. Nothing escaped the aluminum bell housing  but I did rub the boiler plate scuffing my paint a little less aggressively  lightened flywheel and I was racing the  next event. 
I did switch to Ferodo DS 11 pads and Girling Chrimson  racing brake  fluid and never had another problem. 
 

My point is that  there is a point where failure occurs but failure  does not equal disaster.  
On a personal note like Japan in my youth China is discovering better and better quality control. Prejudice aside some Chinese made products are as good or better than American made similar items. Some not all.   
   As a racer you can wait for others to ensure you can safely use a product. But by then prices will have risen. To the point where risk is no longer rewarded because the risk isn't there anymore.  
Complex subject. Risk vs  reward.   Safety lies in following the herd but success lies in leading the herd. 

It isn't just the balancing, it's the metal quality and if there's inclusions if they are machined managing stress risers...

My bet is you see it more on the high hp cars because there's more of them spending the effort on an aftermarket flywheel at all. 

It's just not a part I would cheap out on.

The turbo Miata came with a 1.6 eBay clutch and flywheel.   It didn't have enough clamping force and spun the clutch (a lot). So when I replaced the assembly I went ACT.   And of course the street flywheel was sold out and I had to piney up a few sheckles more for the street-lite unit.    Stupid overkill but it it's peace of mind not having to replace it in a couple of years.

**while sadly acknowledging that the motor has crapped out and I'm replacing it this fall.

ShawnG said:

d_jabsd said:

it's a hunk of metal with a ring gear, know what I mean?

 

If it's that simple, just make your own.

If the cheapo unit shakes, you'll have to go back in to put the good one in anyway. If it comes apart, it will cause more than the cost of the flywheel in damage.

Cheap chineseium parts go where they're easily replaced or won't cause too much collateral damage.

Centrifugal force operates on an exponential scale, not a linear one. There's a lot of force on a flywheel at 5000 rpm.

Boss9 on a dyno with a cast iron flywheel: https://youtu.be/FOnachbSjno

i don't have the means to make my own, so i'm not saying it's that simple, but i guaranteed you it isn't $300+ x 1000+ buyers complicated either.  i'm tired of paying for R&D that was paid off decades ago.  Everyone needs to make a profit, but you don't need to screw people over in the process.  

Your video isn't really relevant. ivy not running a berkeleyton horsepower 429. it's a miata with at most 250hp.  i want something decent, but am not looking to pay for some owner's kid's class in college with a single purchase. that is really where things have gone on simple parts.

do the math. 100% profit for fidanza, act, whomever makes flywheels for FM and SuperMiata.    

if i'm just screwed and that's what i have to do, so be it.  just looking for real world experience.  a crazy 429 on an engine dyno is not real world experience. 

The SFI certification does add a cost to every single unit. FYI. 

The car might only make 250 hp, but that flywheel will be spinning at 7000 rpm pretty much permanently. I would personally be more concerned about long term high stress use than a dyno run or two. Dumb place to save a couple of bucks IMO. There's a reason the SFI standards were created in the first place. 

Horse power does not break flywheels. RPM , vibration, and bad machine work break flywheels. I have seen several come apart on engines that make less than 100 HP, and red line at 6500RPM.

Part of what you're paying is good material, part is good design, part is for the guy operating the mill, part is QC, part is packaging, and part is marketing. It all adds up pretty quick  

$300 isn't that much, especially if you've spent the money to make 200+ hp. And especially since it's not just your foot in the line. If you drive on the street, or at track days, your equipment presents a danger to anyone who happens to be close. 

In reply to barefootskater :

The price is  going to be what it is. You want lower price it will evolve risk. Like Japan early on they improved on quality until they exceeded what we we making. China is doing the same in some products they already have met or exceeded our stuff.  
wait until they are further proven and the price will increase. 

In reply to d_jabsd :

A 250 hp 1.8L miata is giving you 138hp per liter.

A 429 is 7 liters, the same hp per liter would work out to 966hp 

I'm no engineer but I'd bet the stresses aren't that far off.

You've been on this forum long enough to know the people other than me in this thread are giving you good advice.

Horsepower doesn't matter, RPM matters.

Flywheels and clutches are not the place to cheap out.  Especially clutches, because the pressure plate spins as fast as the flywheel does and the plate itself both sees all the heat of clutch slippage with no good way to dissipate it AND is designed kind of like a frag grenade.

I've seen a few "flywheel explosions" that were preceded by a heavy clutch slipping event (smoke from bellhousing area) that lead me to believe they were not flywheel explosions but clutch explosions.

Anyway if you want to be cheap, buy a used high quality flywheel, not a new mystery part.

I will throw out there as well, the cheap eBay (Chinese) flywheel I took out of the turbo Miata had pretty significant wear on the mating surface.  And it was only a few years old.  Factory or high end aftermarket flywheels don't do that either.

Here's an opinion: Stock flywheels were engineered to run pretty much forever, and a bit of flywheel weight smooths everything out and makes a car easy to drive. Surface it and enjoy.

The above is what my brain tells me. Lightened flywheels can be awesome. I'd like to see a real statistic on how many people installed and loved lightened flywheels.

When I replacing the clutch in my stock Jetta and took the flywheel to be resurfaced the machine shop was surprised that I didn't want it lightened.  The car is stock, the flywheel will be fine.

And really, is that 10th of a second going to help you on the street?    (Ok, Maybe.)

wheelsmithy (Joe-with-an-L) (Forum Supporter) said:

Here's an opinion: Stock flywheels were engineered to run pretty much forever, and a bit of flywheel weight smooths everything out and makes a car easy to drive. Surface it and enjoy.

The above is what my brain tells me. Lightened flywheels can be awesome. I'd like to see a real statistic on how many people installed and loved lightened flywheels.

That's pretty much impossible - but we do get lots of positive feedback. More telling, we offer a couple of different weights and very rarely does someone recommend a heavier flywheel than the one they bought. 

d_jabsd said:

i don't have the means to make my own, so i'm not saying it's that simple, but i guaranteed you it isn't $300+ x 1000+ buyers complicated either.  i'm tired of paying for R&D that was paid off decades ago.  Everyone needs to make a profit, but you don't need to screw people over in the process.  

You guarantee it, huh?  I'm going to let you in on a little secret: The R&D costs for putting out a new flywheel are simple overhead costs. They're not baked in and recouped by individual project. The only costs like that would be if you were needing capital investments like forging dies, casting molds, or something like that. Otherwise it's literally just about actual production labor, materials, and quantities.

Stock style clutches and flywheels outsell performance aftermarket units by probably 100:1 or more, so they're made differently. Comparing the cost of a lightweight flywheel to a stock style (including 'heavy duty') clutch is simply not a fair comparison. A much more direct comparison would be the price out a 1 disc aluminum racing clutch. Manufacturing, materials, and quantities are much more similar between the two. You'll be shocked at what those cost, even though there is only a fraction of the variation compared to flywheels, since the same physical clutch can used across the full range of flywheel applications.

So lets look at what it takes to make a typical performance aftermarket flywheel...

Buy 12" bar stock of 4140HT steel.

Saw through the 12" bar to slab off a disc of ring gear material.

Turn the 12" disc into a 12" hoop of ring gear material.

Hobb teeth into the OD of the 12" hoop.

QA check the ring gear.

Buy 12" bar stock of 6061-T6 aluminum.

Saw throught the 12" bar to slab off a disc of flywheel material.

Turn the 12" disc into a flywheel blank.

Mill the flywheel blank to complete the flywheel base.

QA check the flywheel base.

Buy 10" bar stock 1045 steel.

Saw through 10" steel bar to slab off a disc of friction surface material

Turn the 10" disc into a friction plate blank.

Mill the friction plate blank to complete the friction blank.

QA check the friction blank.

Press fit the ring gear on to the flywheel and install retention screws. Install friction plate with retention screws.

QA check completed flywheel.

Now each non-QA (overhead) operation involves ~1 hour of setup time. Since we don't sell large quantities of aftermarket flywheels and can't afford to maintain large excess inventory levels, we'll have to run these in batches of 20 for a reasonably popular car. Assuming an average of $150/hr fully burdened machine time labor rate, that's $7.50 per op per flywheel. With 10 direct labor ops, that's $75 just in setup labor for our reasonably popular car...Less popular and it would be half the run quantities at double the setup costs. I'd say you'll also probably do double that (a mere 6min/op) for direct labor run time hours.  So that's another $150, bringing you up to $225 just in labor. Now for raw material we're probably talking something on the order of $25 for 12"OD x 3/4"T 4140HT, $75 for 12"OD x 2"T 6061-T6, and $10 for 10"OD x 1/2"T 1045. That puts us at a total actual cost to produce of $335...Plus the cost of SFI certification. Plus a nominal profit to manufacturer. Plus nominal profit to retailer...And that doesn't even account for the ones that don't sell right away, and are literally just wasted money sitting on the shelf for months/years.

So yeah...Tell me again about how they're 'screwing people over' here.

This why it's so hard to get companies to make quality performance aftermarket parts for any but the most popular to modify cars... There is simply not enough money in it to justify dealing with the majority of cheapskate owners that whine about how nobody makes parts for their cars, but then don't buy the parts when you do because it's 'overpriced'.

And that ^ is where the cat e36m3 in the cabbage.

Thanks everyone. You confirmed what i figured. i should have just bought the flywheel while i was buying the clutch.  I ended up going with the Supermiata flywheel since i i bought their clutch (centerforce based?)  i really just wanted the collective input and it went the way i thought it would. everyone is trying to save money where they can. this isn't the place.  hindsight is 20/20. 

thank you for setting me straight. 

my turbo build is 3/4 of the way there. 

NermalSnert (Forum Supporter) said:

And that ^ is where the cat e36m3 in the cabbage.

I hope I can remember that one.  

Not sure what other opinions are but a competent machine shop can lighten and balance a stocker.  You won't get the same level of weight reduction but I've had it done a few times on Vw 020's and have been pleased for an $80 machine shop build and losing 1-1.5 lbs.  

I'm always worried about stuff like stress risers and inadvertent weak spots with a modified stock unit. Basically, every time is the first time.