Pros and Cons of a lightened Flywheel
 

Can some one more learned than I please tell me the pros and cons of the lightened flywhee. And some information of what the install is like. Thank you. RX*

pros: engine has less mass, and gains and loses speed more quickly, meaning it seems zippier, and when you're tryin' to drive quick can reduce the time necessary to shift. also reduces the amount of power taken up by the drive train (kinda like removing a lot of weight out of the body... same idea as lighter wheels giving more power on a dyno).

cons: can make it trickier to drive on the street, as the engine has less mass and thus less momentum at a given speed. if you're trying to start up a steep hill you'll notice a difference.
they're also not free.

you'll notice a difference...will it stall? Difference is such a vague word care to expand on it?

it won't stall if you adjust for it by giving the engine more throttle... but will it be easier to stall?? yup. how much?? well i don't know that :p.

great info thx guys

As for as price well you could always smoke your tranny as i did,and get free labor.Ive seen flywheels for about 400 bucks now and maybe 350 to 500 labor.

I drove a friend's Miata with a lightened flywheel (he actually took his stock flywheel out and took several pounds off of it at a machine shop). It definitely revved up faster, as you would expect for less rotating mass, but it was not as 'streetable'... it was tricky to get a smooth launch and just not as friendly to driving in traffic.

That being said, when I do have to replace my clutch (hopefully not for another 50-75k miles) I'll probably put in a beefier clutch and racing flywheel in for autocross purposes.

I have a detailed instruction manual (sans photos) in development and I can tell you from firsthand experience two things. First, my manual will make things easier for you if you are doing the swap in your own driveway. Second, the negative effects of a lighter flywheel are not as dramatic as some might make them seem. My 8 drives like a go-cart now. I have a couple of uphill starts on the way to work and the flywheel actually makes them easier to manage. The throttle and clutch finesse does need a minor change but it becomes natural when you work on it. During starts from a light, for example, I have a much easier time managing the "friction zone". Wakeech is correct that shifting is easier. Now it's like butter! The difference in weight between stock and aftermarket will only be about 5-6 pounds when the counterweight is included.

Charles

For an Auto with lightened flies, would you have to do anything to the transmission control? Would it "learn" the new setup? Could it actually stall an auto?

For an Auto with lightened flies, would you have to do anything to the transmission control? Would it "learn" the new setup? Could it actually stall an auto?

I'm pretty sure this mod is only appropriate for manual transmission vehicles. In an automatic transmission, the flywheel and impeller cover in the torque converter are essentially one piece. Additionally, much of rotational inertia in an automatic transmission comes from hydraulic fluid flow in the torque converter. I would imagine there would be no real benefit of a lighter flywheel/impeller in an auto trans. Someone correct me if I'm wrong.

Correct on the auto flywheel concerns, i.e. light flys are for manual trans only. There is such a thing as a lighter flexplate but that is only in extreme racing applications and certainly not for the 8.

I've used lightweight aluminum flywheels on 2 different RX-7's and I love them. I don't think hey are hard to drive on the street at all. The car is just so much more fun. It is a very noticable increase in "usable" horsepower.

Ok, thanks for the info. The reason I asked is that someone had mentioned the "Auto" Flywheel, or something like that, and my head perked up, like...HMMM???

I guess I'll just have to stick with playing with the engine end...underdrive pulleys, etc.

additionally, it could also add 1st gear chatter w/ lightened flywheel.

but it all depends on how light it is anyways..

for me, i prefer shaving some weight off the stock system.

does it change the exhaust note? or rather, does it go vroovroovroovrooom instead of vrooooooom as you accelerate to 9k rpm? I've noticed this on old f1 and lemans clips...

I'm thinking it might b/c of less momentum to smooth things out

Thats called shifting gears, it sounds like that because the ratios are so short in the trans the flywheel wont change the exhaust note, except mybe from the added acceleration making it change pitch faster.. light flywheel is an awesome mod (atleast on my rx7) I run a RB aluminum one and i wouldnt consider it hard to drive on the street at all,.. differnt but not hard.

A lightened flywheel has zero effect on shift time.

A lightened clutch will.

the sound was more like a trilled note than a flat note, musically. I'm not sure if this makes sense though.

wrong dude. a lighter flywheel lets your engine revs drop faster so you can shift and get off the clutch faster.

wtf is a lightened clutch...

A lightened clutch is a replacement clutch with a lower moment of inertia.

Here is how to upshift (correctly) rev to 8000 rpms in 1st, hit clutch to floor and hold, simultaneously lift off throttle and move shifter out of gear and move toward 2nd. Apply firm pressure, but do not jam shifter any harder than it will go. Give the synchonizer the required time decelerate the clutch to match the new angular velocity of the new gear selected. Now come off the clutch and then put throttle back to the floor. Done.
now for 2 to 3 fell free to go to 9000, 3 to 4 8500 4 to 5 9000, 5th-warning buzzer :)

From 1st to 2nd, the clutch speed has to drop from 8000 (or higher depending on tach latency) to ~4750
2nd 9000 to ~6250
3rd 8500 to ~6000
4th 9000 to ~ 7500
5th 9000 to ~7500

While giving appropriate time for the viscous drag of the gear oil to help brake the clutch (0.1 second) and time for synchro to do the rest (another 0.1 second) the engine is already slowing down (no throttle and no fuel) and its velocity will be matched when the clutch is released. That is why it is important to let the clutch come all the way up before the throttle is reapplied.
This is how to bark the tires if the engine speed is much greater than the new clutch speed, such as keeping the gas floored and bouncing off the rev limiter.

That's all fine and dandy- but in all my years I still don't think I've heard of a 'lightened clutch' either. The material on racing clutches is beefier if anything- the only weight savings to be had in the tranny is in the flywheel.

Race clutches are not lighter clutches. In fact the strongest clutches have multiple plates and are heavier. The spring tension and puck surfaces are different but clutch weights are really insignificant in relation to other clutches.