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You can find endless information on why you shouldn't run a lightweight crank pulley, however I haven't found anyone claiming they personally had issues. Anyone running or been running a lightweight, non dampened crank pulley? Experiences? More specifically; alta, craven speed, m7 stock size aluminum pulleys.
what is it that people just cannot grasp that would make you think that having an undamped crank pulley would ever be even a remotely good idea.
All cranks have vibration. The only ones that you could say "dont" (because if everything is balanced component wise the engine design is naturally harmincally stable i.e. inline 6, boxer 4, some others), but in reality, nothing is perfect and you will still have some slight harmonic vibrations.
What do vibrations do you ask?
well... they vibrate... usually in harmony with the block. And thats a good thing! (when they match perfectly)
but!
IT does cause lots of problems.
This is why you didn't see 4 cylinders in F1. Cosworth tried in the 80's, but every time they went for 12k rpms, and 5 bar of boost, the crank would vibrate too much and cause a critical engine failure. (lots of load, high frequency, caused the crank and engine mains to vibrate at different frequencies, or at least in a different phase of frequency, causes metal to hit metal as its rotating at high load and speed... and well.. not a good idea) (They blew up that motor within a few minutes of sustaining that load and RPM btw... and the entire test field shortly after. Then they found that was the problem and designed an entire new engine around it)
Now obviously we do not rev that high, as well as we are not trying to stuff 5 bar of boost into the motor, but then again, chances are your bottom end isnt blueprinted and perfectly balanced either (the crank probably is rougly balanced, but that is about it )
so for us, and un damped crank pulley mainly means shortened bearing life on your bottom end.
You are imparting additional stresses to the bearings as the crank tries to vibrate around not in harmony with the block, and seeing as the crank "floats" on an oil film inside of the bearing metal pieces, well, hopefully you can see why that may be a bad idea.
Especially when unlike a honda where a set of bearings costs $40 for all 8 half shells (4 cylinder)
ours are over $25/half shell, and a crank is $900
it will not give you any real performance gains to go to a lightened pulley.
It will allow your engine to rev faster, but if you want to do that, you have other things to worry about as this engine just was not designed to do that.
Too much throttle volume, heavy flywheel, heavy crank pulley, long(ish) stroke
if you want info as to why you should not run a un damped crank pulley, its not just applicable to mini's.
now, most of these reasons are only truely applicable in the lifetime that you will have the car if you raced it every day. If you toodle around like a grandma,
A. I suggest getting a different car , but
B. the increased wear will be so small you may not notice a difference.
If however you are racing it, or taking it into the upper rpm's every day, do yourself a favor and get a new stock one (if yours needs replacing) or an aftermarket fluid damped one.
The OE rubber ones actually do a better job at damping (rubber is just better for that), but do not cover as wide of a range as the fluid ones do.
So for racing where the engine is seeing load over a more dynamic range, the fluid ones are still better.
Another great reply on theory and hearsay, I'm talking actual evidence! These pulleys must sell or they wouldn't make them. You don't need to sell me on a damped pulley (I'm not gonna touch one because I don't want the quicker rev drop) but I'm one who needs to see proof saying it will harm your engine. No one has produced this yet, maybe bmw just over engineered another part. (Like the power steering system)
The pulleys do sell. To people who do not care, or people who do not know.
As I said, they will work fine, for a while.
I dont expect you to have an engineering background, but as for evidence, just do a little google searching, I am not about to post loads of it up here.
It is an inherent part of any IC engine, and the engineering on it is quite plain as day.
The fact that you want some sort of numerical proof would require hundreds of cars with three different types of pulleys and doing a statistical regression on the data. Sorry, none of us have that kind of time or cash.
F1 teams and auto manufacturers do.
If non damped cranks worked, they would use them. Believe me, they are a lot cheaper to make.
We have been using them and selling them since 2005, I don't know exactly how many MINIs have been running them, at least hundreds.
I would have to agree that is not the scientific data soccerbummer is looking for, and a small company like ours cannot afford it like he says. He is right, there is not data to back up the claim that this is a safe mod. I do have an answer to the OP question though, of all of them we have sold none have led to any sort of engine problems. I have had two or three pulleys break though when we used the 'spoked' design instead of the solid. That is why we have made them without the spokes for the past few years.
I would offer an alternative reason for the rubber damper on the OEM crank though besides 'overengineering', and it would be saving cost. The stock part is cast. Meaning that they can be made by the thousands for very cheap. The problem with a cast part is that they cannot be made to a tight enough tolerance to be balanced properly. Having the rubber allows the part to balance itself when rotating. A machined billet part like ours does not require balancing because it is perfectly round and balanced. Again, I can't prove that they use the pulley they do in order to save $20 a car, but if you don't think they would save $20 per unit any way they could then you are not a car manufacturer.
Soccerbummer is right, the data is lacking and you always mod at your own risk. Just know that when you use a CravenSpeed part that should an issue occur, we will resolve it. Our parts are guaranteed for life.
seeing as you may also want a bit more background on "why" it is suggested to go with a damped crank, I will insert the blurb from wikipedia (its fairly accurate, but concise) on crankshaft torsional vibrations.
Crankshaft torsional vibration[edit]
Torsional vibration is a concern in the crankshafts of internal combustion engines because it could break the crankshaft itself; shear-off the flywheel; or cause driven belts, gears and attached components to fail, especially when the frequency of the vibration matches the torsional resonant frequency of the crankshaft. Causes of the torsional vibration are attributed to several factors.
Alternating torques are generated by the slider-crank mechanism of the crankshaft, connecting rod, and piston.
The cylinder pressure due to combustion is not constant through the combustion cycle.
The slider-crank mechanism does not output a smooth torque even if the pressure is constant (e.g., at top dead centre there is no torque generated)
The motion of the piston mass and connecting rod mass generate alternating torques often referred to as "inertia" torques
Engines with six or more cylinders in a straight line configuration can have very flexible crankshafts due to their long length.
There is inherently little damping in a crankshaft to reduce the vibration except for the shearing resistance of oil film in the main and conrod bearings.
If torsional vibration is not controlled in a crankshaft it can cause failure of the crankshaft or any accessories that are being driven by the crankshaft (typically at the front of the engine; the inertia of the flywheel normally reduces the motion at the rear of the engine).
This potentially damaging vibration is often controlled by a torsional damper that is located at the front nose of the crankshaft (in automobiles it is often integrated into the front pulley). There are two main types of torsional dampers.
Viscous dampers consist of an inertia ring in a viscous fluid. The torsional vibration of the crankshaft forces the fluid through narrow passages that dissipates the vibration as heat. The viscous torsional damper is analogous to the hydraulic shock absorber in a car's suspension.
Tuned absorber type of "dampers" often referred to as a harmonic dampers or harmonic balancers (even though it technically does not dampen or balance the crankshaft). This damper uses a spring element (often rubber in automobile engines) and an inertia ring that is typically tuned to the first torsional natural frequency of the crankshaft. This type of damper reduces the vibration at specific engine speeds when an excitation torque excites the first natural frequency of the crankshaft, but not at other speeds. This type of damper is analogous to the tuned mass dampers used in skyscrapers to reduce the building motion during an earthquake.
And as I was stating, depending upon engine design, many of the "day to day" driving forces could be absorbed in the lubricating fluid (oil cushion) that the crank and rods float on, but this is not good enough for "more spirited" or "race" conditions where all of these forces are multiplied.
"I know what the point of an air foil is, but how is the experience on a 787?"
well... it works just like an air foil on any other plane. It may be a different size, and a slightly different shape, but the purpose and function are the same...
(perhaps a smidge of hyperbole)
but I guess a direct answer is
There have been no adverse side effects that can be factually linked and stated they were caused by using an undamped crank pulley in an r50 or r53 mini (to my knowledge).
That is not to say there has not, or the gear boxes of half of the cars that do will have wear beyond repair by 150-200K miles, but hey.
I run a craven 2% balancer and a valeo clutch kit standard old school flywheel which is much lighter than boat anchor factory dual mass one and no issues for over 75k. Oh, 17% SC pulley too with 10 psi at 5k feet elevation.
Ask WAY, I have seen him report in one of these threads that he has seen excessive wear issues in a lot of Mini's and a common factor in all of them was a lightweight crank pulley. Here is another good read on the matter.
Ask WAY, I have seen him report in one of these threads that he has seen excessive wear issues in a lot of Mini's and a common factor in all of them was a lightweight crank pulley. Here is another good read on the matter. http://www.atiracing.com/products/da...mper_dinan.htm
I do remember reading a post from WAY, saying he seen a few engines with wear and one with a rod knock. I take anything WAY says seriously because he knows his ****.
^^ fun fact, the deteriorated stock one on his website under the ati listing (yes the one that is split in two) is from my vehicle.
We had to change it in a garage of a grad student who did some side work with him from time to time (mechanical engineer masters student that did mini work for some side cash. LOL!)
but as I have said. You see that stuff on cars with and without the crank pulleys. He has seen enough to build a heuristic sense about normal wear and tear and probably can correlate subconsciously that he has seen less wear on a car with a damped pulley of similar mileage and a similar driver, thus confirming what he (and everyone else) already knows about torsional harmonics and the damage it can cause to bearings, gear boxes, clutch life, rods bearings, crank fatigue, etc, etc, etc
2005 MINI Cooper S. I put a 2% crank pulley on about 3-4 years ago when my car had about 30k miles. I noticed some vibrations at WOT while on the highway. It was hard to pin point but I noticed around 50-60mph. I’m in Pittsburgh and the roads around here are all terrible. I wasn’t sure if I was paranoid or maybe my tires or both! My car has about 38k miles now. Everything was running fine. No noticeable noises. I’m currently doing a rebuild. To my surprise I found a piece of main thrust bearing in the oil pickup tube. Here are a couple pictures. You can think what you want, I’m convinced this is the result of using the 2% pulley. Bearing material from oil pick up tube-caught up in the screen. Damaged main thrust bearing-side view Damaged main thrust bearing-top view
Thank you for sharing as we warn people against them all the time.
Originally Posted by MattyB88
2005 MINI Cooper S. I put a 2% crank pulley on about 3-4 years ago when my car had about 30k miles. I noticed some vibrations at WOT while on the highway. It was hard to pin point but I noticed around 50-60mph. I’m in Pittsburgh and the roads around here are all terrible. I wasn’t sure if I was paranoid or maybe my tires or both! My car has about 38k miles now. Everything was running fine. No noticeable noises. I’m currently doing a rebuild. To my surprise I found a piece of main thrust bearing in the oil pickup tube. Here are a couple pictures. You can think what you want, I’m convinced this is the result of using the 2% pulley. Bearing material from oil pick up tube-caught up in the screen. Damaged main thrust bearing-side view Damaged main thrust bearing-top view
, but 
