Destroying the dogma: lightweight crankpulleys

[i3igpete]

if you recall from vibration analysis, mode shapes are unitless. all they have is frequency (listed at the top of each mode shape as i've presented) and direction (X,Y,Z,Xrot,Yrot,Zrot). the rotational speed of the crankshaft doesn't factor into the natural frequency, only the force-response.

[hotGTO]

@i3igpete:

Are you saying the low RPM frequency, ie: accelerating from a low speed in 4th gear instead of downshifting to 3rd causing a low resonating vibration, is not bad for the engine in the way the high RPM vibrations are?

[i3igpete]

yes, they are two different things. one is your engine mounts getting beat up, the other is your crankshaft twisting.

[bluemax_1]

@i3igpete:

Are you saying the low RPM frequency, ie: accelerating from a low speed in 4th gear instead of downshifting to 3rd causing a low resonating vibration, is not bad for the engine in the way the high RPM vibrations are?

yes, they are two different things. one is your engine mounts getting beat up, the other is your crankshaft twisting.

I just thought I'd clarify this for any noobs reading who might get the wrong impression:

What Pete is saying is that they are 2 different things, the crankshaft's resonant frequency causing the twisting of the crankshaft that can't really be felt by the occupants of the vehicle (rubber mounts are great at attenuating higher frequencies) vs. the engine assembly hitting a resonant frequency that makes the whole assembly vibrate, which can be felt in the car.

That said though, lugging the engine in a gear that's too low can be a different kind of bad for the engine. Doing this can trigger detonation (low rpm, high load) which can be all kinds of bad, but a different bad from what the harmonic damper protects the engine from.


Max

[hotGTO]

I just thought I'd clarify this for any noobs reading who might get the wrong impression:

What Pete is saying is that they are 2 different things, the crankshaft's resonant frequency causing the twisting of the crankshaft that can't really be felt by the occupants of the vehicle (rubber mounts are great at attenuating higher frequencies) vs. the engine assembly hitting a resonant frequency that makes the whole assembly vibrate, which can be felt in the car.

That said though, lugging the engine in a gear that's too low can be a different kind of bad for the engine. Doing this can trigger detonation (low rpm, high load) which can be all kinds of bad, but a different bad from what the harmonic damper protects the engine from.


Max

I didn't figure either was good, but it's good to know the difference between what "vibration" is causing a specific kind of damage and how it relates to your driving habits and/or maintenance routines and/or parts choices... so any time you guys who are "in the know" can translate it to us admitted hobbyists, it helps us know the science behind what we are talking about, and what we see hear and feel when we drive, and helps us make informed choices. So Thanks!

[mb7050]

So what do you think of this damper ?
I have heard nothing but good things about these dampers in racing applications in fact they're proven on some of the fastest Aussie cars around perhaps fastest GTR's/RB's and 1fz´s, 2jz´s anywhere in the world !
some people prefer this over ati .




METAL JACKET Harmonic Balancers / Crank Pulley Dampers

A World First In Balancer / Damper Design !! Encased Dampener Within Balancers

Introducing a revolutionary development in torsional dampening technology. Utilising the ROSS Tuffbond original elastrometric bonding process to produce the ROSS Metaljacket® series harmonic balancers / crank pulley dampers.

Metaljacket Harmonic Balancers/Crank Dampers designed and manufactured by ROSS.

Metaljacket use the highest spec. 6000 series alloys along with aerospace 7075 hard anodised crankshaft hubs.

Metaljacket is designed to be used on race machines that are driven by enthusiasts on the street, strip,circuit or on the water.

The accessary drive pulley ratios are standard unless requested.

These are the worlds best used by world champions.

* 360 timing marks at 1° intervals
* Adjustable timing disc, for TDC accuracy
* Precision CNC machined 40 Tonne tensile alloy steel hub and vibration dampening ring
* Dampening ring and hub permanently bonded together on TWO axis by our exclusive Tuffbond elastrometric bonding process, ensuring maximum harmful vibrations are absorbed.
* balancer is anodized for durability and appearance
* Absorbs more damaging torsional harmonic vibrations
* Quicker engine acceleration
* Increases engine life
* Lifetime warranty, even for racing use - a world first!
* Never requires maintenance or rebuilding - ever!
* Rated to 1500 HP
* Encapsulated MetaL Jacket® design exceeds AN DRA and SF1 i8.1(USA) requirements
* Fits standard or modified engines
* Affordably priced

So

"We can make a batch of dampeners to suit the 6G72.

We would need a sample.



Your price for 1 6G72 metal jacket dampener would be $614.25aud +
tooling & freight
x 2 dampener $583.53aud per dampener + tooling & freight
x 3 dampener $552.82aud per dampener + tooling & freight
x 4 dampener $522.22aud per dampener + tooling & freight
x 5 dampener $491.40aud per dampener + tooling & freight"


so it would be 484.5 USD if 5 or more people would buy but remember shipping from Australia might be pretty pricey ... not a bad price at all remember this damper costs up to 600 USD for most applications !

I actually prefer this damper over ATI mainly because it doesnt need maintenance or rebuilding - ever and lifetime warranty ...

[mb7050]

[hotGTO]

It's beyond me how anyone could throw 10-20 grand into building a 600+ horsepower 3s but skimp on the damper and not be willing to pay a few hundred to help protect the investment. As soon as I get anywhere near 500 hp (maybe another year) I will be in looking for one, but I will have to make do with oem until I can afford that.

[bluemax_1]

mb7050,

that's a pretty decent price for an aftermarket damper. It appears that it's an elastomeric damper that is non-tunable though. One of the things about the ATI dampers is that they build them to general specs and builders can then have the damper dyno tuned specifically for THEIR engine (if they choose to). To dyno tune them, they make pulls on the dyno with equipment measuring the vibration frequencies and they then change the elastomer rings between different compounds (and they might be able to change the mass of the inertia ring too).


Max

[mb7050]

Fluidampr and most of the dampers from Japan for 6g72 are non-tunable + they cost up to 2k.

I was thinking that Fluidampr is the best IMO. there is no best between these dampers until actual testing is done ...
Fluidampr can go bad its not that superior as advertised, Silicon does have a life span. And unfortunately It doesn't have a way to check the fluid to ensure it isn't going bad so you never know !
http://www.metaldyne.com/metaldyne/s...e_testing.aspx
http://130.15.85.212/proceedings/pro...apers/A746.pdf


kinda unbiased test but ...
ATI vs Fluidampr
http://www.fluidampr.com/FACTS.htm

when they make a custom damper they need to know at least

they need the oem damper
the snout of the crank in three different parts
stroke of crank
weight of crank
weight of flywheel
max rpm
max power

more values , better outcome.

http://www.atiracing.com/pdf/custom-damper-form.pdf

it should be pretty good right out of the box.

http://www.atiracing.com/products/da...ting/index.htm
yeah but VERY expensive and i think in most cases unnecessary.