R34 Gtr Advice Please: Power Limit - Nismo Clutch + Dual Mass Flywheel

[iwanta34gtr]

All good guys, cheers for the info.

[MrStabby]

Firstly, sorry to iwanta34gtr for hijacking his thread, this discussion needs it's own thread.

Again, bottom end balancing should be carried out as a complete rotating assembly, correct?

If you dramatically change 1 part (eg reduce your flywheel weight by half - lets say 6kg), will it not throw out the balance of the bottom end? Yes it will.

Dual mass flywheels are designed to deliver a smoother power delivery with less vibration, correct?

So ineffect, do dual mass flywheels in a way, function the same as a vibration dampener? I would say yes.

So, by removing the dual mass flywheel & fitting a single mass flywheel are you ineffect allowing a higher torsional frequency to occur at certain points in the rev range? I think so, hence my original statement.

Adam, why would you only balance a rotating assembly if it was externally balanced? Any rotating assembly should be balanced regardless of how it is balanced!

Yeah, sorry iwanta.

> If you dramatically change 1 part (eg reduce your flywheel weight by half - lets say 6kg), will it not throw out the balance of the bottom end? Yes it will.

No - if the new and old flywheels are both in good balance it will make no difference to the balance. It will change the frequencies that the crank/flywheel assembly resonates at, but thats the twist along its length, not the rotation. Think of it this way - lets assume the crank is infinitely stiff, so it cant twist along its axis. Now lets say one of the big ends is heaver than the rest, then as it rotates around its axis it will produce vibration. Try putting something eccentrically weighted in a drill and see what happens.

Now if we assume the crank is perfectly balanced, but is not perfectly stiff (ie its like a big spring), then it wont vibrate in a radial direction. If we now sit on one end of the crank and look at the other end of the crank, we will see the other end twist forward and back a little, due to the action of the rods applying force to it. This twist will put no force at all on the mains bearings, unlike an eccentric weight.

I know i didn't describe that well. I think about it some more and see if can work out how to describe it better.

> Adam, why would you only balance a rotating assembly if it was externally balanced? Any rotating assembly should be balanced regardless of how it is balanced!

I might not have described it well. For an internally balanced motor, you balance the crank/rods/pistons together. The balancer and clutch assemblies are balanced separately (they should be supplied balanced) so you can swap one well balanced clutch assembly with another well balanced clutch assembly without having to pull the motor apart to rebalance everything, as stated above by GTRPSI.

With an externally balanced motor, there will be eccentric weights on the flywheel and/or balancer, which form part of the crank counterbalancing so in that case you have to balance the balancer/crank/rods/pistons/flywheel together.

But again im not an engine builder, so i'm only moderately confident i understand this stuff.

[533 RYC]

I know & understand the processes & finer points of balancing an engine, as I build engines.

Replacing a flywheel is all well & good as long as it is zero-balanced.

Most manufacturers will either dowel a flywheel to a crank, or, eccentric bolt a flywheel to a crank for the purpose of balancing. In some cases this is done for timing purposes (Rodeo V6, as the crank trigger is on the flywheel)

My flywheel is dowelled.