.......check out section 4.2.1 of this write up ( http://motoringfile.com/files/MCS_Powertrain.pdf ) available from MotoringFile.com

This may answer some questions and will definitely raise some others.

Do you vendors have any comments?

 

Section 4.2.1, exerpt:
"The basic engine for the Mini One and Mini Cooper is fitted with a conventional torsional vibration damper at the front end of the crankshaft. Calculations and measurements showed that the addition of the supercharger with its relatively high moment of inertia was resulting in excessive torsional vibration at about 1600 rpm. This solution was unacceptable both acoustically and in terms of component strength.
The torsional vibration damper used on the Mini Cooper S engine therefore has the belt pulley additionally isolated elastically from the secondary mass, with belt drive vibration damping. Vibration amplitudes are significantly reduced by the isolated belt pulley. However the decisive factor is that the most marked resonance is shifted into a zone below idle speed and is therefore outside the engine's operating range,..."

It will be interesting to see if there are any reported failures due to non-damped crank pulleys...

 

Interesting....any one else want to chime in on this?

 

Due to previous experiences with previous cars in the world of aftermarket parts, Mini-Madness does not produce, and will never produce a lightened crank pulley. This is purely our view on things, and we feel perfectly fine with our decision. Sure they sell like hotcakes, but we cannot see ourselves selling a product we would never run on our cars.


On "other" car engines, replacing the harmonic balancer with a light aluminum crank pulley, can cause VERY serious mid-long term effects.

Out of respect for other vendors I will say there is no proof of this happening with the current MINI.

 

it seems alta might be the ones that should answer to the vib dampener question, as it is one thing that prevents me doing the crank pulley..

pilo racing's crank pulley is heavier, but it has the dampener... i'd be interested to hear any feedback from current alta owners over harmonics...

 

..."the supercharger with its relatively high moment of inertia was resulting in excessive torsional vibration at about 1600 rpm. This solution was unacceptable acoustically and in terms of component strength."


These words are very vague and really, in and of themselves, do not point to any pending doom for those that remove the damper. From them we know that the design engineers were first concerned about the noise coming from the engine and more was bad. We also know that without a damper the design of some of their engine components probably were closer to some limiting safety factor. Without knowing the magnitude of the additional vibration at 1600 rpm, its impossible to tell if its matter for any real concern. I would venture a guess that folks have modified their cars much farther out of the design engineer's "factory" comfort zone. Will removing the damper be the straw that breaks the camel's back for those highly modified cars? I seriously doubt it. But I guess it might depend on how long those cars are driven around at 1600 rpm . Time will tell I suppose. But seriously I do believe that some performance oriented car builders design more flexibility in their original components anticipating to not be beyond and meaningful safety limit even with aftermarket tinkering.

 

I seem to remember a recent thread either here on on MINI2 about a lightened crank pulley causing supercharger belt failure? There was a video with it. Is this ringing a bell with anyone?

-Dave

 

Yes, that video was from onasled. In the end he wasn't torquing the crank pulley bolt down enough- once he had the correct torque setting, all was good. onasled, does that sound right??

 

As mentioned above, this problem is not unique to the MINI and as such comes as no surprise to me. I can think of far better ways to spend your money than a lightened crank pulley.

 

the Alta Q&A thread covers it as well. Comes down to it's bad in theory, but there is little evidence that the Mini really suffers significantly from it's removal. But trueth be told, the number of cars reporting long use with one is small, but most report no problems. Statistically, this shades the perspective to it not being as bad as other cars. But the confidence in the claim is weak at best, due to small sample size.

There is a lightened dampener available from one company. There is rumour that the 05 crank pully is lighter than the 02-04. There is a very light Al pully (no dampener) available on eBay for about $40..... Caveat Emptor!

Matt

sp, search on the words "crank pully" and you'll se about a half dozen threads that speak to the issue. -M-

 

Yes, this is basically right. I did not torque the pulley bolt correctly and the pulley started to come of, thus destroying the belt.
This time I added a lock washer also.

 

The paper is basically right - with a solid crank pulley you can observe a slight resonance at about 1600 RPM. This is really only noticeable when you're putzing about a parking lot in 1st gear [bogging the engine].

The paper forgot to say the resonance is not a noteworthy reliability concern, but an NVH/psychoacoustics concern.

Of note in the article; nowhere does it mention the torsional damper actually does anything; it's the elastically isolated pulley that quells the NVH.

 

If the harmonic vibration at 1600 rpm really put the design engineers into an area of any meaningful conern of component failure, do you think they'd be writing about it in a publication? Wow, the whole engine just blew up because my very critical elastomer lost its bounce and hardened up over the last 6 years . Too funny!

 

Some sell lighter flywheels and non-spring clutch hubs. I would theorize that such mods would contribute more to vibration/resonance than lightening a crank pulley which is always churning against a fanbelt/supercharger belt. the fanbelt/ supercharger belt would tend to dampen the vibration at all times, I would think. I haven't heard of any bad things happening to the crank bearings on account of those changes. On the other hand, maybe the additional vibration might damage the accessories run off the front of the engine. But then again, the engines running lighter flywheels, at least on the v-8's and such I have heard, tend to idle rougher and that would seem to be tougher on the accessories also.

Is it really just a NVH issue or are there really some longevity issues related to the crank pulley? I thought Randy was going to give the pulley some thought and testing and report back. Inquiring minds want to know. Frankly I am hoping for a good report since the lightened and enlarged crank pulley would seem like a reallly good mod.

 

FWIW, the issues other cars have brought to light WRT lightweight crank pullies has to do with damage to the oil pump, not the crank bearings. As the oil pump runs off the front of the crank, it is first in line to absorb and vibration not absorbed by the crank pulley, and is subject to failure. I know this has been an issue in the Miata world - not sure of others.

There have been no reported failures in a MINI, AFAIK.

 

Just checked Randy's forum:

"I'm not quite ready to put the seal of approval on it..."

http://store.webbmotorsports.com/ind...aaeb6ac8934455

No explanation given.

 

I had a good long talk with Randy a couple days ago, and this came-up. He, and one of assistants have each had one installed for a few months now (0 and 2%). I wish not to misquote him, so I will not attempt to do so. Suffice it to say, he's not ready yet to endorse this mod.

As far as not being aware of corresponding failures, I too am not, at least for a street-driven MINI. And if one believes that the track has a way of speeding-up what happens on the street, then concerns for that person would be valid. Another perspective is that track cars live virtually their entire life above 4 and 5k RPM, where the normal street car certainly does not; and with that, the impact might be 100+k miles away, possibly more, or less. Ah, time wil tell... as always...

 

That could mean several things:

1. He is working on releasing his own version, at which time it will be endorsed

2. There has been a failure and he doesn't want to sabotage someone elses product

3. He hasn't broken it yet- still testing

 

OEMs put harmonic dampers on engines to reduce the vibration that causes excess wear to items driven off the crank: timing chains/gears etc. because they want to ensure the engine won't wear out during its warranty period. These dampers are tuned to absorb the frequencies seen with a stock engine, and if modifications are made (eg a 19% pulley) then the frequencies produced may no longer be in a range that the damper can absorb. So it is perfectly possible for a stock balancer to be as useless as a lightweight pulley (which is always useless at absorbing vibration) if the engine is modded.

Hotrodders will spend $400 on aftermarket multifrequency harmonic balancers like the "Fluidampr" http://www.fluidampr.com/torsional_vibration.htm not only for the reason of reducing wear. Camshafts (and distributors on older cars) are affected by these vibrations and the result is timing fluctuates and this costs power; the amount depends on how much slack is in the timing chain. The problem gets worse as wear accelerates, and it is obvious how this random "variable valve timing" or ignition timing can hurt horsepower.

If you have ever turned a camshaft assembly by hand against the valvesprings then you can imagine how much vibration that can produce at high RPMs. A Roots supercharger at speed will induce strong pulsations into the belt as well. A forged crank will "ring," as these vibrations generated at the front of the engine are absorbed only by the flywheel at the back of an engine, and metal fatigue is a bad thing.

 

...but we already have lightweight flywheels installed. Lots of tracked cars I think have done this. So there is a lot less absorbing in such cases. So shouldn't we expect then all sorts of bad thing to be happening to folks that put in lightweight flywheels? Anybody out there that dumped the weight of the stock flywheel experiencing premature wear, more heat, etc?

 

The point of having the damper up front is to reduce the torsional vibrations where they are generated from the cam drive etc. before they twist all the way back to the flywheel.

Flywheels have so much inertia they can even mask the big power pulses from cylinder firing to prevent them from being transmitted to the driveline and causing NVH problems there. So nothing gets past the flywheel, but because of their location, neither heavy or light flywheels can do much with the back-and forth twisting at the front of the engine. Since a flywheel stores the energy and gives it back later, things continue to ring and you can sometimes get a resonant frequency. Think of it as a spring.

Harmonic dampers work in an entirely different manner-they convert the vibrational energy to heat. The flexing of the elastomer or shear of the silicone fluid or the rattling of ***** (the TCI "Rattler" must not be used in knock-sensor equipped vehicles) generates heat in dissipating the energy. Think of it as a shock absorber, since those also convert energy to heat.

A dual-mass flywheel may also convert vibrations to heat so be aware that replacing one with a simple flywheel will reduce the ability to dampen vibration.

Whether just letting things twist away is bad or not is pure conjecture without statistical data. Just because one car didn't wear its bearings faster won't prove much. All I can say is that BMW tested a fleet of cars to 100,000 miles (from the JCW we can conclude that the 15% pulley is OK with the stock balancer) and they decided to spend the $5 per car to put the balancer in, so why take it out?

 

So, heat is ok on the shaft that the bearing is connected to?

 

Yes, and it is important to note the shaft (crankshaft) is also connected to some things moving from gasoline fires

It's not a lot of heat (your shocks don't glow red hot either) but if the energy is not dissipated as heat it has to go somewhere. Losing the dual-mass flywheel, for example, means converting that vibrational energy to noise. Why it's noisy: https://www.northamericanmotoring.co...5&postcount=10
Lot of people complaining of rattling noises with a light flywheel on this board.

 

In the paper about how to upgrade the MINI power plant from 118 to 163, they specifically address the damper.

The single mass damper had a strong resonance in the normal operating range of the SC and engine.

The Dual mass damper moved that resonance down below the idle speed, thus out of the range where it would be a problem.

John

 

Small amount of heat means small amount of noise which means no problemo. I guess we'll have to keep watching for reported failures attributable to these non damped crank pulleys. There are more and more out there. Can't tell much from the vague tech words that are written as to if it is a first order concern or not. Putting on the miles will likely be the way to tell.