After reading through
@SharkyUK project thread, he's used a heavier than normal flywheel so maybe he can offer some advice as there must be a reason he has gone that route?
Thanks for the heads-up mate
Please note that this is my understanding of the situation and I may be wrong. That said, I did take advice from people in the know and followed their recommendations...
The important thing to note is that whether or not you use a lighter (or heavier) flywheel is very much down to the nature of the tune of the engine, the components being used and the results you are looking for. There isn't really a one-size fits all answer (hence the myriad of replies and views across the Internet on this subject). It's entirely possible to have a flywheel that is too light so that you are quickly into high rpm but the turbo hasn't hit the optimal spool and the flip side of the coin being that you have a very fast spooling turbo but your engine is not up to speed into the optimal power band (remembering that turbo rpm and engine rpm aren't directly related).
In the case of my own build I am not using a massive turbo where lag is likely to be a big issue (although the power I'm looking for will be a substantial leap over stock). With the F4R engine naturally being a fairly free-revving engine there really was no requirement to lighten the flywheel in a bid to increase the rate at which the engine will rev on (or drop revs off) the throttle. Considering the build as a whole the more important factor was (as Dan points out) the requirement to put more load on the engine to get it working harder (to load up the crank train) and to get the exhaust gases flowing (to help the turbo spool up). As said, this setup is tailored to my build so different people with different engines, compression ratios and turbo sizes will likely use different weight flywheels to suit their needs. The heavier flywheel will also make my car a little easier to drive when pulling away and from lower speeds as I'm effectively not having to 'slip' the clutch as much. A light or heavy flywheel isn't so much to do with handling power (which is more a function of the clutch) but is a balancing act in getting the optimal engine loads and turbo spool to achieve maximum effect at the right time.
A larger turbo may require a significant increase in engine load to ensure the turbo spools up and builds boost effectively. It's possible that a very large turbo build may have the scenario whereby the turbo cannot generate the boost quick enough to keep up with the engine rpm and consequently never hits maximum boost levels.
But beware, there is also a LOT of misinformation out there. I think a lot of people just fall into the trap of, "ooh, a lightened flywheel - it must be better!" This is not necessarily the case.
Disclaimer: I'm not an expert, this is my own personal view of things
