Crank pulley vibration dampers & harmonics. Update: Lightweight crank pulleys = Bad

Ah - did a diagnosis / spec change come from it?

 

yea, fit th factory damped pulley on it..
Swindon did'nt remove it, the local guys operating the car did as the owner bought it as an upgrade

eak! then the carnage ensued.

Fluid Damper claim power gains from fitting their damper on BT cars over the stock damper from improved control of harmonics.. Skeptical I am, but its plausable I guess

Longevety on a higher revving motor is my own motivation.
I know mines sweet revving and vibration free to 9krpm, despite race engine mounts etc

Not yet seen a customer car as smooth..
Difference between "balanced" built motor, and one which has been assembled with drop in rods I guess

 

I presume Swindon put the damper back on, when rebuilt & running ok since? Still with internal trigger wheel?

So this is an aftermarket item?

I wonder if engine mounts have their part in "harmonics"?

FPA engine from Autosport 2009, bog standard vibration damper?



Other pics checked - there's no external trigger wheel on it.

 

you would think the F2 engine (with external timing disk and no damper) would be more powerful and rev a bit more than the FPA motor

the F3 atmo engines have no crank damper

very confusing

 

The common theme is revs.

Bill - do you have an indication of what was being asked of the Leon?

 

Just been reading a bit about this and apparently critical harmonics can shear both the front pulley and flywheel off the crank

hmm.....flywheels coming off........that old chestnut

I have plenty of egs where these dampers are not fitted to atmo race engines - perhaps the increased cylinder pressures seen in turbo motors cause greater imbalances in the crank....dunno though, serious maths time

 

mid to high 8krpms
450bhp+


mine runs one of these

http://www.fluidampr.com/VOLKSWAGEN.html

not cheap. and heavier than stock damper pulley

more info here on vortex
http://forums.vwvortex.com/zerothread?id=4672798&postid=62349044#62349044

 

Fascinating physics:

Did yours have this fitted before, or is it just on the new build?

 

I fitted it along with the new turbo setup last year. Its not run long, longer on the dyno than on the track thus far

As I was upping my rev limit for the new turbo, it seemed a good thing to do

 

So is it literal, as in full of fluid, or does the mass of it damp out the vibrations/harmonics?


A conversation today about the topic of vibration dampers, referencing the Swindon example:

"Was the crank balanced?" (ie that's the biggie)

"Where road engines sit at constant revs eg on a motorway, the harmonics start to build up, but where an engine is up and down the revs (ie race engine) it's not the same."

<gist of convo>

The emphasis seemed to be on 'constant'.

 

Silicon fluid in it of some description.
more info on their site I think

The broken engine was a fully balanced race engine yes. does not account for harmonics tho which is why crank damper is req'd (imho)

Constant is not relevant to me.. and not the case on the engine which expired. On track round Silverstone, testing.

 

Im not convinced by the Damper theory.

What springs to my mind is the other end of the crank and the forces being applied here, what happens to the crank every time the clutch plate is engaged, at speed and at high revs?

What forces will this apply to the crank? i can see it twisting the crank, and forcing it against the thrust bearings. Wont the torsional forces be quite high? higher than the forces from a solid crank pully?

 

<thinking aloud - deliberate non-engineering speak>

Those are lateral 'abrasive' forces against the thrust bearings, as opposed to rotational 'whip' (where anything out of balance gets amplified with every increase in revs).

 

Some more reading:

http://www.fluidampr.com/howitworks.htm

http://www.fluidampr.com/problem.htm

 

Bill has headed in the right direction. The only problem is being able to identify if the damper that is being used is able to cancel the harmonics that may occur at certain critical engine speeds for a specific application. Hopefully this research would be done by the company supplying the part for a custom engine.
Having a lighten crankshaft pulley to free up accessory drive losses may seem like a good idea to some, but I am afraid they may need to refine their knowledge of what physics is taking place inside engine as the crankshaft bends, flexes and twists. Without an appropriate damper you are asking for potential problems.
This maybe the issue on high rpm ABF motors that seem to shake loose the 60-2 trigger wheel, assuming the fasteners were torqued with loctite. But then most of the torsional issues occur furthest away from flywheel.

I have used dampers (ATI) a lot on built Skyline RB26DETT motors that required revs in excess of the 8000rpm limit.
Does seem to stop the oil pump from blowing up.
On another note I remember, when I did not know better, making a pulley from a chunk mild steel on the lathe and mounting it on a 4AGZE motor to increase supercharger revs and boost. This lil 1.6 200bhp engine span to 7500rpm and boy did it get there regularly!. In the end the crankshaft broke at the snout!

My favourites revealed a link relevant to this subject by BMW Tuner Dinan,
Please read.

The Danger of Power Pulleys & Understanding the Harmonic Damper
BY STEVE DINAN OF DINAN BMW


www.atiracing.com/products/dampers/damper_dinan.htm

 

if they are so critical, why are there so many race engines that dont have them, and dont blow themselves to pieces?

 

Conversely, if they aren't so critical, why did the Swindon Leon engine literally fall apart, and why does the Fluidampr exist? [1) product to sell, 2) engineering basis, albeit contained in marketing blumf]

Could the difference be down to turbocharging, and the effects this could have on harmonics, crank twist etc?

 

The very recently developed turbocharged VW F2 engine doesn't have one - one would think this has been through adequate development cycles at Mountune, who are no mugs

 

Of course it doesn't have one, but Swindon are no mugs either, yet the 1.8T engine which blew apart on a Neuspeed pulley belies their huge experience.

All we can really say at this juncture is that the evidence is very confusing and conflicting.

 

The link in toyotecs last post pretty much covers the whole subject. It makes an interesting and informative read by all accounts.
The variation in components materials, weights and the engines rpm mean that there is no simple fix for all circumstances and may explain why some engines do not give issues and others do. Probably more by luck than design as the time and equipment required to measure these harmonics is probably beyond the remit of most engine shops.

I can see manufacturers in the R&D stage of design using sensors all over the block when the engine is running to pickup and measure forces then design a damper suitable to damp the harmonics out.