Miata Turbo Forum - Boost cars, acquire cats.

- Suspension, Brakes, Drivetrain (https://www.miataturbo.net/suspension-brakes-drivetrain-49/)

- - Help me pick a clutch? (https://www.miataturbo.net/suspension-brakes-drivetrain-49/help-me-pick-clutch-91551/)

Quote:

Originally Posted by ridethecliche (Post 1381215)

What do you mean that transmissions hate that much torque? I thought six speeds were fine for 300?

you are joking right?

Quote:

Originally Posted by bbundy (Post 1381245)

you are joking right?

He's new and still reading and learning.

RTC, 300hp on the street is much different than 300hp on track. Think duty cycle.

Quote:

Originally Posted by sixshooter (Post 1381221)

If we had stronger transmissions available we could go lighter on the flywheels with relative impunity. We need better transmission options..

Need T56 adapter plates.

Quote:

Originally Posted by hi_im_sean (Post 1381246)

He's new and still reading and learning.

RTC, 300hp on the street is much different than 300hp on track. Think duty cycle.

Also tires, the purple crack tires have grip. There may be something too the heavier flywheel damping out the pulse peaks but I have broken enough transmissions to know it isn't close enough to make a big difference and I've broken transmissions with a 1.8 liter organic sprung disk on an 11 lb flywheel just as I have broken them with a 1.6l 4 puck unsprung. The lighter the assembly is the better it feels to me however.

Quote:

Originally Posted by bbundy (Post 1381251)

There may be something too the heavier flywheel damping out the pulse peaks but I have broken enough transmissions to know it isn't close enough to make a big difference.....

This is my feeling on the subject. While the theory is sound and it make some difference, I think the severity is over blown. For example: it might make a 300hp motor appear as 295hp to the gear teeth cyclical loading, instead. Again, just my intuition, no hard data for our specific circumstances. All the articles I posted in the original thread for that discussion, that keep getting referenced, refer to airplanes and prop reduction boxes.

Oh right. Slicks change the equation entirely since they stress the trans far more.

I was just wondering if the lighter flywheel was part of the reason for greater transmission stress. Kinda like how the damper needs to get changed at higher power.

I know these things aren't directly related, but mostly looking at things that need to be done as you push the power up!

We call all seasons on high HP cars "transmission fuses" for a reason.

How are you going to drive the car?

Take what you've learned about the flywheel and throw it in the trash. From what i've gathered, it's all about feel.
I've chose to save cash.

Soon as you start hammering gears and wheel hopping the game is over. The clutch and flywheel doesn't care, everything behind it does.

Troof

9lb F1 ebay FW here. No ragrats.

This pic was taken behind Bob Bundy's house:

http://i58.tinypic.com/5mi985.jpg

https://cimg5.ibsrv.net/gimg/www.mia...5d58c1bd1a.png

Quote:

The flywheel also performs another function as well, one of smoothing the engine's power pulses. As the engine turns, each cylinder goes through two distinct phases - the compression stroke and the power stroke. On the power stroke, the piston is driving the crankshaft. On the compression stroke, the crankshaft is driving the piston. Thus, for every other revolution, the crank alternates between "being twisted" and "twisting." The flywheel absorbs energy on the "being twisted" phase, and then returns the energy on the "twisting" phase, helping to smooth the engine pulsations. On a single cylinder engine, this pulse damping is of significance. On a one hundred cylinder engine, the pulses would be distributed so evenly that the flywheel damping would not be needed. For this reason, a heavy flywheel would be of less benefit to a V8 than it would be to a four cylinder engine.

The damping effect of the flywheel is also assisted by the damping action of the harmonic balancer. In addition to the "flywheel" effect of the relatively heavy damper, the elastic material between the inner and outer portion of the harmonic balancer adds to the smoothing effect. This elastic material absorbs some of the "being twisted" forces, and gives back during the "twisting" phase.

Just throwing it out there that the mean torque of a 300wtq engine is a long way from the momentary torque of the same engine. It appears to easily be twice as much. A larger flywheel lowers the peak and raises the valley, evening the energy out. A flywheel is an energy capturing and releasing device, an energy storage device. Would you want over 600ft lbs of force on a couple of gears in the transmission at one instantaneous moment if you were trying to protect it, or perhaps instead smoothing it a bit? It depends on how much you enjoy the lightweight flywheel's responsiveness versus exchanging transmissions, I guess.

So increased chatter with lighter flywheels could also be due to this loss of dampening?

I wonder if folks have tested the clutch/flywheel combo with significant decel chatter and swapped out to the stock flywheel and found that the sound goes away. I know it's understood that it's a function of the lighter flywheel but increase in NVH means less damping, no?

https://www.miataturbo.net/suspensio...h-83376/page2/

If you read the links I posted in there, you'll find that until you model the engine and trans, find their frequencies and determine the crossover points, any talk of damping beyond reasonable amounts (like having the harmonic there and any FW) is useless. In other words, 20 lbs of FW may be no more useful that 10lb on a given engine tranny combo, as 5 may be enough to damp any and all pulses to a satisfactory degree. Conversely, 20 could also have double the damping effect as 10 on a given combo, and that engine/trans may need 30lbs to be happy.
https://www.miataturbo.net/suspensio...2/#post1213618

I like the FM level 2 clutch lots of torque capacity, good pedal feel, and smooth engagement. That said I did somehow manage to break the sprung hub on the clutch disk on a FM level 2 clutch kit. I don't think it had anything to do with quality of the parts but most likely my lack of mechanical empathy and a trip to deals gap.

Quote:

Originally Posted by Lee04vr (Post 1387170)

I've seen that failure a couple of times, seems pretty easy with aggressive driving or tracking.

Quote:

Originally Posted by curly (Post 1387232)

I've seen that failure a couple of times, seems pretty easy with aggressive driving or tracking.

rigid disk fixed the problem of blowing the sprung center apart for me.

Quote:

Originally Posted by curly (Post 1387232)

I've seen that failure a couple of times, seems pretty easy with aggressive driving or tracking.

I'm a big fan of the ACT clutches and that's what I always recommend customers based on my testing. I haven't run an FM clutch, but from what I understand they are made by Competition Clutch. I have had the same experience with a Comp clutch road race Honda - the sprung hub just fell apart. I also replaced it with an unsprung disc and it was fine, if you're okay dealing with the unsprung hub. Ultimately it got replaced by an Exedy stage 2 (again, Honda application) and it was much better.

The ACT HD street clutches we've been getting people with their K swap kits have done very well and are rated at 245 tq with the organic disc.

I'm displeased with my FM1 clutch; I was extra vigilant not to go into boost when driving. I followed FM recommendation to ensure proper break in, and the clutch slipped when I tried to hit WOT in 4th gear. The clutch had over 500 miles on it.

I wonder if FM can do anything about it?

On a happier note, the 10lb flywheel is awesome.

Not trying to hijack this thread but..... My car makes 215 wheel torque. Bought car recently and believe it has FM Stage 1. Throw out bearing squeals a lot but clutch doesn't slip. About to replace whole assembly with either FM Stage 1 or 949 racing clutch kit. Afraid the 949 might be too weak for my power.