Viscous Dampers Front Pulley
Turbo Mini Forums

ahh i see more rpm gives the chance of more torque is that due to the engine breathing more at more rpm? given the air flow
you say cam choice makes a difference as you may know i have the md247 injection one that i plan to use
it has a 1-6k power band so my question is can cams make torque past the rated rpm band? ie i didn't think i had planed on using such light internals with this cam there for i can probably rev it some more if the cam still makes the torque right?

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The power curve on my 998 Turbo fitted with the MD274 was still climbing at 6k rpm, although torque was just starting to fall.

My latest 2 engines have the same sort of cam and they are built to rev to 7k plus.

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i dont agree with if you lighten you internals you will lose torque i think you will lose speed faster when going up hills for instance due to less mass can hold less motion

so im going to be limited but my cam choice to what rpm is useful and making power so i could get away with std weight internals alth i think id still like the other benefits from light internals like spool up/down better engine breaking when you let off witch i can make better with the mappable ignition as well
i think any mass removed with out loosing strength is a good think alto i will not see its full as said more 7 8 9k rpm engines will see much more from it
i do plan to up the boost until im happy with how fast it is might have to start a weight saving mission but id like to stay std looking

the damper im not convinced to go one way or the other yet

Two advantages of using heavy flywheels on low rev engines (7k or less) that most over look, is that they improve standing start launch. Works in the same way as KERS (stored energy). They also help the clutch disipate (absorb) the heat of that launch much better.

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Nothing is impossible it just costs more and takes longer.

I never noticed any real differance between a std and ultra light flywheel, except the car did seem to feel like it was quicker when on the loud pedal but that could have just been me...

I run a supercharger and I don't care the TB is on the wrong side.
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totally agree with you there also help you maintain a steady cruseing speed too

i know this discussion has moved to inertial mass differences- but is there any difference in the harmonic zone for heavy or light flywheel - i am wondering why all the effort at countering the harmonics is at the one end only ( damper end) - is space/design the issue - eg would a rubberised mass near the flywheel help mitigate against harmonics - just thinking out loud -

There are such things as dual mass flywheels on modern engines, which in essence, do the same thing. There are also things called balance shafts, which attempt to cancel out the vibrations of the reciprocating mass that the harmonic damper does not affect.

Lightening the rotating mass is said to move the critical frequency up the rpm band but not far enough for it to be of no concern, it's still there and the need for a damper is just as strong. The fact that the standard damper is now no longer tuned to the new critical frequency means that it cannot do its intended job as efficiently, hence the best option there is to fit a viscous damper, as I'm pretty sure no one outside of high end motorsport will be able to measure or calculate the required changes to the original rubber isolted damper to tune it back onto the critical frequency of the new set up.

Now thre are two things here. The fatigue life of the crankshaft and the loss of measuable power. without a damper the crankshaft life is shortened and there will likely be a measurable loss in power. The fatigue life is easy to understand as its the same what happens to a metal spoon bent back and forth repeatedly until it breaks. The loss of power though is a little harder to understand. This loss of power is down to the vibrations in the shaft preventing the bearings meintianing a proper oil film for them the shaft to run on, an increase in internal friction. The more severe this vibration and the chances are the bearings themselves will fail. The forces at the bearing when the shaft is violently vibrating is said to be much higher than the bearings were ever designed for (I have seen catastrophic failure several times at work due to these sorts of harmonic vibrations).

This is not to say you cannot run an engine without a damper, but the crankshaft fatige life will be shortened and there may be a measurable loss in power if it doesn't kill the bearings fisrt.

perhaps the two part cooper s type damper and pulley with a 36-1 trigger cut in it will be fine for what im intending on doing
after all the crank will be hardened and stress relived so perhaps not to such a big deal about the viscous damper
after all i do already have it and its brand new so it makes sense to spend the 500 odd aud bucks on something better

like a modern turbo or a nice aluminum one off intake manifold with built in water to air charge cooler i can see the pictures in my head already = )

i'm considering this to be decision made.. thanks guys for bring forth good info