Orpheus

i have the competition clutch / science of speed ultra light flywheel. it's one piece steel, and i weighed it at 8.6lbs on my shipping scale:

https://www.s2ki.com/s2000/topic/840...pp-exedy-hyper

besides the toda, which is about 50% more and only about 0.3lbs lighter, this is the lightest steel flywheel you can buy, and even better it's not expensive. EDIT: i should also note, it did not exhibit any "clutch buzz."

as for driveability, yeah, you're gonna have to launch at a little higher rpm. but in my opinion, if you have a hard time launching still, and don't like quick revs, the s2000 is not the car for you.

SgtB

I daily drive an ACT. It really isn't bad at all. I don't know what all the doom and gloom is about. Sure the center may have more mass, but it's pretty evenly distributed throughout the disk. Again, it's very easy to drive. I don't even have to think about it.

prj3ctm4yh3m

I daily drive an ACT. It really isn't bad at all. I don't know what all the doom and gloom is about. Sure the center may have more mass, but it's pretty evenly distributed throughout the disk. Again, it's very easy to drive. I don't even have to think about it.
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I agree with you, its not that hard to get acclimated to as far as driving goes. My only point was that there was a noticeable increase in engine braking; something people overlook.

Saki GT

F=m*a - If you remove mass from the flywheel, you will need to increase acceleration from the engine to get the same force. With less mass, acceleration inputs, either from you or from the connected transmission, play a bigger role.

timg

I had a fidanza with a SPEC stage 2 clutch. The flywheel exaggerated the clutch buzz and made it a bit more difficult to drive. I got back from a month in Scotland driving a manual transmission car that I never stalled once, and stalled my own car backing out of the garage... I sold the flywheel when my engine was rebuilt.

Tim

Orpheus

in theory yes (i assume you mean when the clutch is engaged), but the inertia of the flywheel is quite small when compared to the overall drivetrain and rotating assembly in the engine. there will be very little difference in response to "acceleration inputs," probably none you can feel. but, the real difference is when the clutch is disengaged, because the intertia of the flywheel is significant compared to just the engine's rotating assembly, which it is connected to. revs will move much faster, and engine speed may match the trans speed faster too when engaging.

Saki GT

Yeah, one point I want to point out is that when the system is fully engaged, the flywheel mass is less important, and free revving the car in neutral is not what you will get when driving.

SpitfireS

Saki GT Posted Yesterday, 06:32 PM
Replace "in neutral" with "while clutch in" and you have a rev match downshift.
Happens all the time, with or without braking.

slipstream444

While illustrative to your point, F=m*a is not the correct formula to use here. I believe the correct formula is t=I*(alpha). t is torque, I is moment of inertia and alpha is angular acceleration. "F" is measured in Newtons or Pounds; torque is of course measured in foot*lbs or Newton*Meters. The moment of inertia has to be calculated - it's not stamped on the flywheel (none I've seen at least). This takes experimental apparatus or testing equipment to accomplish.
You're not moving a static mass in a linear fashion. The relationship is different when considering rotational inertia, and dependent on where the mass is concentrated in the diameter of the flywheel. The overall mass of the flywheel (in the example of the S2000) is not as important.
You can have two 10 lb flywheels, for example. The flywheel with the greatest concentration of mass furthest out on its diameter will require more torque to accelerate. In reality, you can have a 10 lb flywheel that is harder to accelerate than a 12 lb flywheel, if it has a greater concentration of mass further out in its diameter.

How much difference (in reality) does a lighter flywheel on an S2000 make? The exact amount is impossible to know unless you know what the OEM and aftermarket flywheel's moment of inertias are. The difference I note in my S2000 is related to the speed and ease of rev matching, not any difficulty in starting out. But then again, I have an AP2 transmission and 4.44 gears in my AP1, and getting 'over the hump' at initial startup is not an issue. I've in essence (not through deliberate action though) compensated for any increased engine torque requirement at initial startup (b/c of a lighter flywheel) through torque multiplication (lower gear ratios) in the transmission and diff.

In real world terms - the only time I could see the lighter (lower rotational inertia) FW being an issue is if you have a stock diff ratio and you drive in stop and go traffic a lot. Otherwise - it's not that big of a deal.

Saki GT

Thanks slipstream for getting specific - I was trying to simply point out conservation of energy principle - in general, there is always an effect to a change somewhere in the system. Whether or not its noticeable or better or worse, that's different. There are many variables to consider along the way too.