Likely hood of a spun bearing
 

I have a turbo on the stock motor @12lb boost max. If I have a light weight flywheel, drive shaft and pulleys am i more likely to spin a bearing or would that be less of a factor?

Not that I really have a good answer but are you asking more likely than stock or if there would be a different part that would likely fail before that?

EDIT: I would also guess with my limited background that proper oil levels would be significantly more important than pulleys or flywheels.

It can happen anytime on stock or non stock engine. Just depends how you drive it. If you go all out 5th gear you'll probably spin a bearing. Flywheel and all that really doesn't matter to much.

Yes to both... I think what i'm really asking is will the lack of rotational mass will have any adverse affect on the internals.

If you're worried about nvh affecting internals maybe you might want to look at replacing the lightweight crank pulley with a fluidampr. From their website:

"Fluidampr® – Sport Compact Engine performance upgrades increase the naturally occurring characteristics of harmful crankshaft torsional vibrations. By installing a Fluidampr viscous damper you will reduce wear on the main bearings and timing gear, achieve more accurate valvetrain operation and lower the risk of crank failure. Unlike rubber based dampers, Fluidampr automatically adapts to your modifications, then continuously self-tunes in real time to optimum damping at both peak levels and across a broad changing frequency range. As the engine revs up, torsional vibration suspends the inertia ring and reduces its weight felt on the crankshaft. Measured as rotating weight, this effect helps maintain quick revs while preserving optimum dampening. Must have for instant protection against turbo and NOS power surges. Features precision machined and computer balanced components. Never needs to be tuned or rebuilt."

Would you like to expand on that ..... ya lost me ..... :(


humfrz

Boosted. You do a 5th gear pull all the way to top end it puts really really heavy loads on the engine. Say you're accelerating foot to the floor in 5th or 6th. Well how long are you above 4500 5000rpm? Quite a while depending on power level. Hot oil temps, heat soaking intercooler, coolant temp goes up. It's all recipe for spun bearing or rod through the side of the block. Basically all I'm saying is the harder you push it the more likely you are you toast your engine. I've been in a wrx that my buddy was doing a quick pull for data log and got a little frisky and went into 5th and stayed foot to the floor for about 20 seconds then pop smoke done.

so what I can tell from their a quick google of the product, it is used balance the crankshaft against spikes across a wide RPM range. all while maintaining an almost stock weight and HP/ TQ

The big causes of spun bearings are:
1. Bad tune causing detonation which hammers the bearings flat and screws up the clearances (more often than not a bad tune will crack a piston ringland before it will cause you to spin a bearing)
2. Low oil pressure - this can be caused by low oil, a cracked oil pickup tube, or too much high lateral G driving pushing the oil to one side of the pan and starving the pickup tube. Baffled oil pan could solve this issue, or ...don't drive it to its limits.
3. Using oil that is not specified for the engine (and its modifications)

A good quality quality oil cooler is always a good investment on any forced induction 86\brz

sustained hard driving (even a few minutes) with forced induction usually sees oil temps rise significantly with forced induction

I have one installed.

When speaking about a "spun bearing" that usually implies a rod bearing.
The concern about the lightweight pulleys and FW is for the main bearings.
Just to keep it in perspective.

And yes based on commentary by a respected member on this forum (cant remember right now) having BOTH a light weight FW AND lightened pulleys increases risk of damage to the main bearings.

which would be more advantageous? the flywheel or the pulleys...

Reducing the rotational inertia of the FW can make a huge difference.
In fact reducing it TOO much can make the car undriveable


Reducing the rotational mass of the crank pulley is negligible.
(unless you use an underdrive pulley it will not be noticeable)


If you use a LW FW, you should use a fluiddamper pulley