Originally Posted by pasta
^^^^he is 100% correct save your money aluminum isnt going to make any gains
I'd disagree. Gains in power, no not noticeably. But technically if the flywheel is lighter, than less energy is used on changing it's rotational rate and more energy can go into changing your wheels rotation rate. Less rotating mass isn't going to give you more power really, but marginally more power will reach your wheels, if that makes any sense. Don't expect to be able to say X hp gains though.
The gains are in power delivery. I LOVE my 12 lb Al flywheel, the engine revs up much more freely than with the stock 24.5 lb steel flywheel. So no I don't have gains as in a lot more horsepower, but the delivery of my horsepower is much more fun. It's a matter of Drivability gains vs Power gains. Similar in concept to lighter wheels making your car feel like it's a little faster. Less rotating mass for the engine to accelerate allows the car to accelerate faster.
I'd suggest waiting to get a Al flywheel till you need a clutch, but it will be necessary to pair them. For instance, I have a Spec Clutch, so I need a Spec Flywheel.
Al flywheels have a steel plate that bolts on where the clutch disc makes contact with the flywheel, frequently called a "friction pack". Once you get a clutch and Al flywheel, when you need a new clutch many thousands of miles later, instead of machining the flywheel surface like you would on a steel flywheel, you spend the $80 or so on a new "friction pack" for your flywheel.
So no, not worth you trying to swap out just a flywheel right now (unless you are racing and really need to affect your power delivery). For street driving, just wait till you need a clutch replacement and consider it then. The trade off is going to be some clutch chatter and easier to stall it when starting from a stop, but personally, I'll gladly take that to get the fun factor
I will caution you though, listen to a SVTF with clutch chatter and find out if it annoys you before considering buying an Al flywheel and performance clutch. I ride Ducati's with multiplate dry clutches that rattle like crazy, people think the bike is broken at red lights!
So comparatively I never understand the problem with clutch chatter on my SVTF. Which is why I wholeheartedly recommend the light Al flywheel and performance clutch when it's time for a new clutch. But I have seen a LOT of threads of people very annoyed at the noisy clutch. Also I've had a fair number of people get in my SVTF and ask "WTF is the matter with your car??!"