Lighter flywheel?
 

I don't know how many of you do cycling, but the cycling market is always preaching about removing weight from your wheels. SO every time you pedal, you move that much less weight around. Well, would replacing the flywheel of a clutch with one a bit lighter possibly improve FE?

I know that performance car people do that.
You get a slightly rougher idle.
Any reduction in rotating mass helps, especially in acceleration. Not sure how much it helps FE in steady state travel.

That's also the original concept behind "mag" (magnesium) wheels and alloy wheels. Less rotating mass. Of course nowadays it's mostly about bling. If you want a lightweight wheel you really have to pay attention to the specs.

phantomcow2 -

I also heard that it helps performance, but the shifting gets harder, aka difficult to engage "smoothly".

CarloSW2

Aluminum flywheels are great for improving hp, I'm sure it could be worked backwards to benefit fe instead. Any weight removed is good, esp/ rotational mass..

the lighter the flywheel the more you are going to have to crank up the idle speed as well, and the easeyer it's going to be to stall your car when taking off from a dead stop as the flywheel is what smooths out the bumps in your engines speed with every rotation, I think it also might hurt your torque

It improves acceleration, has no effect on steady state driving like on the freeway or climbing hills (aside from strict weight reduction). If you do alot of in-town driving you may see some effect. Try it if you are already doing a clutch job, otherwise not worth it in my opinion.

While it's all apart, pay attention to clutch and pressure plate balance, check and balance each item before installation. Some cheaper parts are way off.

Oh well I would never change it out just because. My clutch is original and has 273,500 miles on it! The master cylinder was recently replaced though.
But sooner or later it will fail on me, I'm just looking ahead.

Some of us don't use the clutch anyway Well, except for first ;)

I assume you are sugesting shifting without useing the clutch? I've been in peoples vehicles that alwas do that, and after a while the transmition has so much slop in it that it's scarry, even tho they are still able to shift smooth-ish without the clutch, I would say that for longevity of your drive train that dubble clutching would be the ideal way to go, because your syncronizers have very little stress on them, leaving less particals from wear floating around, leaving you with a tranny that will last almost forever.

If you are replacing your clutch at some point, have it ballenced like was said befor, rotaing mass that is out of ballence is not efficent, of course no one is going to get it perfectly in ballence, so ask around as to what a number of shops find to be an acceptable range, and ask how close to perfection they can get, just like when car tires are ballenced the weights only go down to a quarter ounce or so, but when I ballence my own motorcycle wheels I get much closer by useing lead solder insted of stick on weights and might get within 1/20 of an ounce of being in ballence, and they spin without any vibration.

The flywheels in the VX civics are 3 lbs lighter than all other model civics.

I personally turned down a stock flywheel on a civic from 20lbs. down to 11.25 (balanced to within 1 gram) and had no ill effects on driveability. It had a positive impact on FE as long as you weren't giving it more gas since the car accelerated so effortlessly. ;)

I agree that one should not shift without the clutch. It's there for a reason. I rev match all my shifts, it makes for a smoother ride for me and passengers, and is more gentle on the transmission.

TomO, did you just use an engine lathe to turn yours down? I've got access to a 13" engine lathe if I need it. How much runout is permissible?

It was a CNC lathe. What my friend and I did (he was the one running the machine) was we took off all the backing weight on the OEM flywheel. basically it's all the dead, non-functional weight that Honda put on the back-side. It's the same place they remove some excess weight for the VX flywheel as well. It's been going on 3-4 years now with 262HP and 213ft/lbs of torque going through that lightened flywheel. Recently inspected, it showed no signs of stress fractures or heat scorching even with a 6 puck sprung clutch kit on it.

So how thick is it now?

Basically the thickness of the teeth on the flywheel and the mounting surface for the crank.