Custom 8.5" Clutch shenanigans
 

So for a while now I’ve heard about this local clutch god’s mom and pop shop… everyone swears by him and apparently he builds custom application clutches for high HP cars. I figured my Act full face was not going to cut it and I was going to need either a 4 or 6 puck for my build.
I decided to him a try, and as far as customer service and just being a cool dude I came out extremely happy.

Anyways, (cool story bro)

The dude really knows his shit. I was impressed, he really knew the Miata application, including the to various disk sizes (1.6 vrs 1.8) right off the top of his head. After a while of bullshiting and him talking way over my head about the technical aspect of various clutches and their applications.. He told me that a sprung 4 puck would be pretty dope. However, because of my sissy pants we compromised on a 6 puck sprung for better daily driving.
Also, he told me that he would use a 8.5 “smaller” disk for better rotational mass. He assured me that the smaller disk would not fault performance. I trust him.. however, I’m curious as to what others think?

Here’s some more information
PP: Act XT, which he tested at over 2200Lbs of force (resurfaced)
Fly: Act 1.8 Prolight (resurfaced)
Disk: Custom 6 sprung 6 puck. Because of the resurfacing on the PP and fly, the width of pads were compensated for no loss in force (Which I thought was pretty cool).

He said with this PP, it should have no problem with upwards of 325 lb-ft if not more..

note: ID of pad circle clear both disk edges. No hangover.

https://www.miataturbo.net/attachmen...ine=1398233183
https://www.miataturbo.net/attachmen...ine=1398233183
https://www.miataturbo.net/attachmen...ine=1398233183

I'm not sure why people try to save mass on the clutch. I mean, even with the lightest flywheel and the heaviest clutch available for our car, the clutch still weighs about 1/3 as much as the flywheel. Stock it's less than 1/10.

Reducing flywheel weight is what gives you that quick revving in neutral. When you're in gear, there's no difference between a 7 lb flywheel and a 20 lb one. I guess a light clutch would make you rev faster when you're out of gear with the clutch engaged, so I suppose it would help if you double clutch your downshifts. Otherwise I see no benefit. No real disadvantages either, though.

Did you get a part number for the new clutch?

Part number?

The clutch was custom built.

??? The slight diameter difference probably won't show much wight savings but I'm sure is better for performance . Its got to be better than nothing when your not sacrificing performance?

https://www.miataturbo.net/attachmen...ine=1398275112

:facepalm:

I like your user name.

Oh, right, I forgot how a lightweight flywheel is worth 20 HP on the dyno. It's like 4 stickers or half a cold air intake.

Heh man this joke never gets old keep the good times rolling bro

Just because it doesn't add power doesn't mean it doesn't make you faster. Stop talking out your ass like an expert when you don't know basic shit.

Bro, do you even flywheel?

Dude! Put the shovel down and back away from the hole. The deeper you dig it, the farther the fall.

You obviously do not have the experience/knowledge to be commenting on such topics so it's better to just avoid it all together rather than look silly trying to defend an already inaccurate statement.

BTW - this is the nicest comment you will receive from this forum, so do yourself a favor and take my kind advice.

Moment of inertia - Wikipedia, the free encyclopedia

Ignorance is OK as long as you work to get rid of it once you know it exists.

Annnnd you've gone full retard, even though you were warned about not going full retard.

Why do the noobs never learn?

I see we ascribe to the "frees up power that would otherwise be sent to the wheels" school of thought here. Anyone care to attach a picture of a first gear dyno pull showing the half a horsepower it's supposed to free up?

Or is there something else that a lightweight flywheel is supposed to do? I can confirm that mine does indeed make rev matching much quicker, but my gutless 1.6 is still slower than shit. No magical 20 HP gain here.

It was just linked to you.

Moment of inertia - Wikipedia, the free encyclopedia

Stop talking, start reading.

You're probably one of those dweebs that thinks driveline loss should be a static HP number, too. You and Corky Bell would have that in common.

I understand the concept of MOI. What I don't understand is exactly how much inertia you think it has when compared to the inertia of the entire car. Even with the gearing advantage of first, the inertia of the car is still an order of magnitude greater than that of the flywheel. In second and beyond, there is no significant difference at the wheels between a stock flywheel and a lightened one. Even in first a heavier flywheel is better for hard launches because it stores the same amount of energy at lower RPMs, giving you more time in first. So a light flywheel is better for soft launches and that's it. Whoop-dee-fucking-doo.

Oh wait, then there's the reason you actually bought it: it rev matches faster and upsets the car less if you mess up. That's actually a pretty damn good reason to buy one.

Holy shit youre dumb. I like how youre making assumptions about something that you do not understand.

Its not just the reduction of weight. Say you have a car with a 20lb flywheel and an identical car with a 10lb flywheel and a 10 lb weight sitting in the car. Both cars would have the exact same curb weight, the second car (with the light flywheel) would be measurably faster.
The car is faster because its not having to spin that added weight at 7000 rpm.

In Herb Adams book "Chassis Engineering" he says:
He goes on to create an example in which a car minus 15 pounds off the driveline at crank speed (e.g. flywheel, crank, etc.) creates an improvement in acceleration equivalent to 32 horsepower.

That's almost 7 stickers worth.

:rofl:

If anybody wants a good read, check out this old thread I participated in:
tungsten crankshaft - D-series.org

This guy was even dumber than "failure", he wanted to make a super heavy crankshaft out of tungsten because he thought that the crank carrying more inertia would equate to a faster car... somehow.

Yes, I agree. Nothing I've said is incompatible with this.


I don't doubt that this is possible, but this example car certainly isn't a Miata. Also, this is only true for a single gear, and it assumes the flywheel wasn't spun up before engaging the clutch.

Dude have you ever played Gran Turismo 3? The first mods you always do to a car are LWFW, stage 3 clutch, and carbon driveshaft. They are the cheapest and drop your lap time significantly.

Vidya games don't lie

The Miata is a front engine rear wheel drive car, hardly unique in the automotive world. What makes you think that it would be different?

O RLY!?

It doesnt matter what car it is. It doesnt matter how much the car weighs. All that matters is the difference in rotating mass and the rpm. If anything it may have a greater affect on a miata because we would be spinning to higher speeds than the big V8s that Herb Adams worked with for Trans Am racing.
Yeah, I set my rev limit at 10k rpm, so when I slowly flat shift at 8k I get a clutch raping boost in acceleration. That makes more sense than shifting fast.

Everything you've said is incompatible with that. It's almost like you don't even know what you're saying, yourself.

I never denied that reducing the weight of the flywheel freed up power. Only that it did so by a relevant amount.

You're not trying to imply that 1 lb of flywheel mass = 2 HP, regardless of anything else about the car, are you? I can assure you, my 7 lb flywheel didn't give me 30 HP. How much gain did yours net you on the butt dyno?

...

Glad we're on the same page now. I guess 32hp isn't relevant to you though, seems like quite a bit to me when you start from ~140hp. Though I guess it would be a bit less than 32hp since you're only talking about a 13lbs difference rather than a 15lbs difference like in the example.

Well yeah. It's relevant. That's why we're talking about it.




There's a very important qualifier that you're leaving out.

Yeah, it sure feels awesome putting down 115 + 32 = 147 HP from my 1.6. Apparently I have more horsepower than the 1.8 guys now.

:bowrofl:

Tell me more about how the MOI differs between 1st and the rest of the gears, I'm almost pissing myself I'm laughing so hard.

Where is this whacky theoretical knowledge of yours coming from? You're not a freshman mechanical engineering student are you?

You are so unbelievably short-sighted it's a wonder you can put on matching shoes every day.


Of course, that's an assumption on my part.

I wonder if someone else will point out that you don't know what you're talking about or if they're too busy shitting all over me.

We've got the 'shipped artwork hall of fame' thread and the 'Joe Perez Epic Rants' thread, we need a collection of 'Epic Failures in Physics/Engineering' thread to compile these. I remember the guy who vehemently argued that the most important part of the suspension was the amount of suspension travel, which is why his stock suspension setup was better than everyone who 'ruined their handling' when lowering their cars with coilovers.

Unlikely, as he's not the one that's wrong.

Nobody is saying that a flywheel adds power. There's your hint of the day.

No, they're just claiming that reducing flywheel weight reduces drivetrain losses well into the negatives.

As to why the flywheel has less effect in higher gears, it's not because the MOI of the flywheel changes. In high gear, much more load is placed on the engine from the road, while the load from the flywheel stays constant.

No... nobody is saying it reduces losses into the negatives. I don't know where the hell you got that.

I don't even have a degree and sucked at math past trig, and even i understand what's going on here. Let's keep up, shall we?

The difference made by the flywheel isn't just weight. It will show a change in power on an inertial dyno. The obvious implication of the "1 lb = 2 HP" crowd is that if you removed the flywheel, clutch, and pressure plate and linked the crank directly to the input shaft of the transmission, you would see a change of about 50 HP vs stock. This is manifestly untrue, because where the fuck is that 50 HP going to come from?

It's not "drivetrain losses", losses come from friction.

It's just like weight reduction only the affect is amplified because of the high speed things like the flywheel are accelerated to.
Taking 200 lbs out of a miata might make it accelerate like it has another 20 HP. That doesn't mean if gained 20 HP. Taking this same weight out of the wheels, driveshaft, crank, flywheel, etc. Would have an even greater affect.

We're talking about a measured difference in acceleration of the car here. It is true that an inertia dyno will show small differences in power from drivetrain inertia, but that is just because inertia dyno are retarded. Plus, this discrepancy is relative to the mass of the inertia dyno's drum which is easily 1000 lbs. That is why a flywheel would only have a small affect on its reading.

I'd count the number of times you've contradicted yourself, but i'm too dumb to count that high and suck at math.

Yes, but the difference made by the flywheel isn't chassis weight; it's drivetrain inertia. The flywheel is effectively a container that stores energy. Making it smaller means that you don't have to feed it as much energy as you accelerate, meaning more power reaches the wheels.

I think this is where our disagreement starts from: you guys seem to think that the loaded acceleration benefit of a light flywheel isn't measurable, but I know that it is, and I know how small that measurement actually is.

U SRS right now?


But yes, it certainly is measurable. I don't think you have any idea what the measurement is, though.

Omg a DYNOJET is not REAL LIFE.
It shows a change in output from a change in flywheel mass because it is not a real dyno and the change is small because the drum is heavy as shit.
Inertia dyno's are a cheap substitution for a real load holding dyno, which would show no gains from a flywheel.

Man I wish I wasnt so busy at work to miss this.

What you're missing is the fact that yes, the inertia of the car is a couple orders of magnitude larger than that of the flywheel, the speed at which the flywheel is rotating and the rate of acceleration of the flywheel are multiple orders of magnitude beyond what the car as a whole are attempting to do. Which is where the difference in the acceleration of the whole car comes from when reducing the rotational inertia of the car.

I want to know how much the OP paid for this custom clutch and flywheel setup and if it was even worth it. I hope it was under $600.

And some other things to clear up. The stock flywheel weighs ~20 pounds, the stock and most other pressure plates weigh ~9 pounds and the stock friction disk weighs about 3 pounds. So the weight of the clutch does matter and it makes up ~1/3 of the weight of the clutch and flywheel setup.

And did you know I can make a 10 hp swing on a stock miata engine on a dyno jet just by switching between BALLER 45 pound 18" wheels and silly 7 pound 13" wheels?

Hey Failure, I'm sure it is you alone who are right and all the rest of us are wrong. But since you decided to ignore my earlier warning and now we have 3 pages of stupidity, let me throw this in the works. Ignore acceleration for a minute so you can stop talking about drivetrain losses and horsepower gains. a lighter flywheel will decelerate the car quicker as well, creating yet another performance advantage. But what do I know. What do we know. What do all of the car builders all over the world from history know. I guess nothing, so we should all put big lead flywheels in our rides since it makes almost no difference at all according to you.

In his defense, the title of the the thread does call shenanigans...
Shenanigans?!

Paid 120 for the clutch, 90 for the resurfacing. PP and fly came with the motor I bought so I don't have a price for those. Thanks for your input, I was hoping someone would touch on this..

Pretty funny because that exaclty what i was thinking when titling it. I almost went with "evil shenanigans" :rofl:

And to think that all the other lightweight rotating parts I slaved over all these years were such a waste of time and money. What a pity.

A+ thread.

Did you get it from Tampa Clutch over on 40th Street? He knows race Miatas.

Yes, Jim over at Tampa clutch.

I didn't realize they were still in business. They were always good to us over the years.

Have you been driving with this clutch yet? Interested in hearing about the results.

They are still around, actually they seem to be doing very well since literally every transmission and clutch place I called in the area referred them.

Motor is going in on the 14th of May. After break in, I'll post my findings :cool:

I just don’t get why anyone would stick with the 1.8l size clutch and flywheel if they are worried about rotational inertia. A stock size 1.6l clutch disk is only 200mm ~7.9” diameter. And weighs about a 1 lb less than a 1.8l. The pressure plate in an ACT clutch is about 1.5 lbs lighter for the 1.6l version and a Fadanza 1.6l flywheel is just over 7 lbs instead of something like 9 or 10 for many of the light weight 1.8L flywheels.

The 1.6l ACT MZ1-XTR4 on a Fidanza flywheel comes out something like 18 lbs for total rotating assembly. It is rated to hold 350 ft-lbs. I’ve broken 3 six speed transmissions with too much torque and haven’t changed the clutch or flywheel so I can vouch for its torque capacity. The car is plenty drivable on the street once you get use to it as well.

LA LA LA LA LAAAAAAAAAAAAAAAAAAAA I CAN'T HEAR YOU

Oh its because the mass taken off the flywheel and cliutch is only about 4 times as effective at improving acceleration as if you took it off the weight of one of your wheels. assuming you are in a 1:1 gear and even more in lower gears.

Another little secret. Taking the rotating weight off at your alternator is about 8 times as effective it's got to spin up at ~2.5X engine RPM.

The rate at which things have to spin at has a big effect on the impact of their rotationl intertia.

Fairly educational with math and science and physics and stuff. note in second gear flywheel/clutch weight has a huge effect on acceleration.

The Effects of Rotational Inertia on Automotive Acceleration

I think Failure finally "got it".

Yep, if I were to choose, I would go with the 1.6 Fadanza flywheel. However, (other than the clutch) this package came with the motor , so I'm going to stick with it.

Dude, what about L3 Weight Reduction and Chassis Stiffening?!!!1111