Lightweight Crank Pulley Check-In

[black_gst]

I have the stock dampner now and plan on buying a fluidampr. for me its a "better safe then sorry" mentality. i have this saying i live by especially when it comes to these cars,"do it right or do it twice."

also id like to rev higher then 7500 rpm and a fluidampr isnt a bad idea at that point

if mine goes bad before i buy a fluidampr i would buy a new oem one.

just my .02

 

[dsm-onster]

My main bearings looked new after 210K, 120k, 105k, 63k for the different motors I've pulled that've employed the stock pulley be ing pushed a bit harder. An example of main bearing wear was posted by the thread starter. Top bearing in the picture below; from a 13 second car with only 50k on the motor:

Harmonic balancers are NOT for reducing the transference of the crank vibration to the block and thus the unibody: Crankshaft Dampers 101 - Mopar Muscle Magazine. They are there to stop the recoil of the crank after it twists from the power stroke and piston/rod inertia. It is attached to the crank. It minimizes the forces the crank itself exerts.

Even MachV had a first hand experience to contribute on their website where they sell undamped pullies: Tip 11: Crank Pulleys

 

[DashLaflash]

Yes, that's what this site is for. It's also to have members give suggestions to help prevent others from making mistakes that could cost them a lot of money. Everyone here is simply trying to give as much info as they can so that the original poster can make a good decision.

The solid pulley has widely been said to limit the life of the bearings due to vibrations, and in turn the life of the motor. Again, it may not happen right away, or to everyone, but most engine builders in our market tend to steer people towards keeping a dampener for a reason. Some people don't care about that risk, or they take the risk and are okay with the idea of freshening the engine sooner than they might otherwise have to. If you're okay with that risk, no big deal. But understand that it is a real risk. As others have said, the solid pulley poses a higher risk than removing balance shafts.

See now what I don't understand is how the pulley can have a negative effect on some engines but not others. Aren't they all seeing the same effect with an undampened pulley. This is what leads me to believe it is just poor engine building that leads to the bearing failure. Also notice how this thread has gone from crank failure and snapping to just talking about premature bearing wear. Didn't Buschur racing do a test and report unusual bearing wear with an undampened pulley. Does anyone have any pictures and results from this test or is this also internet myth. What is this unusual bearing wear?

 

[ramsack]

Does an underdrive pulley really add horsepower? The pulley manufacturers say they do, and we've seen tests in magazines that seemed to indicate signficant gains. But you could get the same sort of gains during a drag race WITHOUT an underdrive pulley by removing the belt from your alternator. (The motor can run solely off the battery for a short time.)

That's one of the sanest things I have read, and it is free!

 

[dsm-onster]

See now what I don't understand is how the pulley can have a negative effect on some engines but not others. Aren't they all seeing the same effect with an undampened pulley. This is what leads me to believe it is just poor engine building that leads to the bearing failure. Also notice how this thread has gone from crank failure and snapping to just talking about premature bearing wear. Didn't Buschur racing do a test and report unusual bearing wear with an undampened pulley. Does anyone have any pictures and results from this test or is this also internet myth. What is this unusual bearing wear?

You yourself have a link already depicting unusual main bearing wear . Only 50k with a 13 second 2.0L motor (not with a less "square" 2.4 crank).

A motor that exhibits such unusual bearing wear will also snap the crank prematurely, because what causes the bearing wear is the unsafe flexing of the crank during periods resonance in the rev range. Enough flex over time, and even after replacing the bearings, will break the crank.

 

[ramsack]

This is what leads me to believe it is just poor engine building that leads to the bearing failure.

Yes, Mitsubishi, themselves, put dampened pulleys on these engines because they build engines poorly and wanted to hide that fact

 

[Calan]

See now what I don't understand is how the pulley can have a negative effect on some engines but not others. Aren't they all seeing the same effect with an undampened pulley. This is what leads me to believe it is just poor engine building that leads to the bearing failure.

In an ideal world where everything was machined and assembled to extremely tight tolerances, the dampener probably isn't as critical, depending on other components and your goals for engine longevity. The problem is, there are countless variables that would all have to be tightly controlled in every case in order for undampened cranks to never have any issues....and that's impossible in the real world.

Once in a while everything may come together perfectly and it's fine; but I think most of the time that wouldn't be the case. Maybe the engine builder missed a piston balance by .1 grams. Maybe a bearing was in spec, but just barely. Maybe one or two cylinders are producing 20 psi more pressure during combustion than the other two.. etc etc etc.

Also notice how this thread has gone from crank failure and snapping to just talking about premature bearing wear. Didn't Buschur racing do a test and report unusual bearing wear with an undampened pulley. Does anyone have any pictures and results from this test or is this also internet myth. What is this unusual bearing wear?

Worn bearings would just be the first and most noticeable failure mode. A snapped crank (or other issues) could be likely if the problem persists though.

 

[DashLaflash]

You yourself have a link already depicting unusual main bearing wear . Only 50k with a 13 second 2.0L motor (not with a less "square" 2.4 crank).

A motor that exhibits such unusual bearing wear will also snap the crank prematurely, because what causes the bearing wear is the unsafe flexing of the crank during periods resonance in the rev range. Enough flex over time, and even after replacing the bearings, will break the crank.

This is true but pneumo had already posted on page 2 that the bearing wear seems normal so you guys are contradicting each other. Also the bearings have 98k on them. He just installed the pulley at around 50k.

Yes, Mitsubishi, themselves, put dampened pulleys on these engines because they build engines poorly and wanted to hide that fact

Ah ya my bad I was talking about people that rebuild their own engines. You can't forget about crankwalk though .

 

[turbo addict]

OK I let this go as long as I can. why are all of you making your stock pulleys wet?? it is not dampener you are not throwing water on them, they are dampers.

Ya Craig I know you can't really compare the two and I appreciate your input. I was just saying that if I went on DSMtuners and read that everyone was now using undampened pulleys and having great success with them for many many miles I would go out and get one. Isn't that what this site is for so people can see what set ups to run on a dsm and also how to fix them . I know that's kinda the bandwagon mentallity but look at how many people are now running holsets. Its the new popular thing and for good reason. I definatley don't fall into the category of Curt Brown or pneumo but I do have a fresh engine and change my oil regularly on my cars.

My question to Turbo Addict is why do you run a dampened pulley in your racecar? You seem to be a strong supporter of the undampened pulley.

I dont car either way, and on the race car I have a twin disk. so even more stuff rattling around.
Again I said that I just like to argue.

 

[donniekak]

In an ideal world where everything was machined and assembled to extremely tight tolerances, the dampener probably isn't as critical, depending on other components and your goals for engine longevity. The problem is, there are countless variables that would all have to be tightly controlled in every case in order for undampened cranks to never have any issues....and that's impossible in the real world.

Once in a while everything may come together perfectly and it's fine; but I think most of the time that wouldn't be the case. Maybe the engine builder missed a piston balance by .1 grams. Maybe a bearing was in spec, but just barely. Maybe one or two cylinders are producing 20 psi more pressure during combustion than the other two.. etc etc etc.



Worn bearings would just be the first and most noticeable failure mode. A snapped crank (or other issues) could be likely if the problem persists though.

The need for a torsional damper have nothing to due with tolerances. It has to due with the fact that a crankshaft doesnt turn smoothly. It rotates from being slammed 4 times every 2 revolutions. This causes twisting, and rebound in the crank, as dsmonster said. The damper smooths this out, and also dampens the higher order vibrations caused by it.

 

[dsm-onster]

This is true but pneumo had already posted on page 2 that the bearing wear seems normal so you guys are contradicting each other. Also the bearings have 98k on them. He just installed the pulley at around 50k.

Considering main bearings shouldn't look like that with 98K on them, I still feel its an example.

Pneumo may feel the bearing wear is normal because he has been running an undamped pulley for a long time . But likely from looking at motors with more miles than just 98K and/or looking at bearings from cranks other than the 88mm. . . I feel that is abnormal wear for a 98K 2.0L 4g63.

Mitsu engineers apparently tested and felt that the crank requires a more costly pulley. There is no other purpose for the damper other than to inhibit the recoil of the crank. Cranks recoiling in resonance eat bearings; and eventually breaks cranks for the same reason valvesprings lose strength over time.

 

[ramsack]

If you want a lighter rotating mass, get a flywheel. That's where the most gain is. Stock is about 19 lbs. and a Fidanza is about 8 lbs.

 

[Calan]

The need for a torsional damper have nothing to due with tolerances.

Yeah I know...I was just saying that if everything (throughout the engine) was "perfect", then wear and tear on parts might not be as noticeable and you may get away without the dampener for a longer period of time with no apparent issues.

I completely understand your point though.

 

[Sp1kE]

You guys are worried about a solid pully but you will rip the balance shafts out and let your motor vibrate like a son-of a.......

 

[Calan]

You guys are worried about a solid pully but you will rip the balance shafts out and let your motor vibrate like a son-of a.......

Have you read any of this thread?

 

[tkelly27]

Buschur won't run an undamped pulley either. He was having the same weird bearing wear until he took off the unorthodox and put on a fluidampr.

Unless you are at a high level of racing you'll never know the difference, and all the people at the highest levels of 4g63 power run a damper. It seems pretty simple to me.

Last time this came up unorthodox told me that bolted connections like the crankshaft to crank sprocket and damper to crank sprocket cannot transmit torsional vibrations. I don't really buy that, but if someone could prove it either way I'd be happy to read up on it. Also, conventional logic says that a 4 cylinder with it's stiff crankshaft design doesn't need a damper. I still won't run anything but a stock one.

 

[Sp1kE]

Sure have.
I have a comparison for you.
-You pull the balance shafts and you can feel a physical vibration in the cabin of your car, which is obviously vibrating your entire motor and say that there are no ill effects? aswell as the BS belt has actual tention on it pulling the crank to the one side.

-You use a solid pully and are worried about the torsional force?
If your that worried, maybe you should make a crank with built in dampers inbetween each bearing.
The bearings are still going to recieve that torsional force and vibrate at that frequency until it reaches the end of the crank anyways, passing through each bearing and twisting the crank.

The only time problems will occur is if the engine operates at the same frequency for X amount time that the "waves" will actually double up. Other wise they will just bounce into each other and could even cancel each other out.

Mind you I still got a Fluidampr at a good price so I'm running it

 

[Calan]

Last time this came up unorthodox told me that bolted connections like the crankshaft to crank sprocket and damper to crank sprocket cannot transmit torsional vibrations.

yep... sure sounds like a large load of BS to me.

With 30,000 to 50,000 psi of clamp force on the bolts (not to mention the crank sprocket is keyed), I think torsional vibrations would be transferred just fine. If not, then someone better let the Mitsu engineers know, because they used bolts to hold the factory dampener on.

Sure have.
I have a comparison for you.
-You pull the balance shafts and you can feel a physical vibration in the cabin of your car, which is obviously vibrating your entire motor and say that there are no ill effects? aswell as the BS belt has actual tention on it pulling the crank to the one side.

-You use a solid pully and are worried about the torsional force?...

Ummm...What? The BS belt doesn't put ANYWHERE NEAR the amount of force on the main bearings that the crank itself does. In fact, I would venture to guess that main bearing loading due to all of the accessory and timing belts combined is pretty insignificant compared to the twisting, relaxing, and "jump roping" of the crank due to normal combustion.

You might want to re-read posts 64 through 69.

 

[dsm-onster]

Yea must have stopped on page 2 somewhere.

AGAIN, crank dampers are not for vibrations. They are for minimizing the flex the crank sees because if it being inherently out of balance by design. The forces most certainly ARE reduced. As the crank springs back to it's original form, the momentum maks it want to flex beyond that in the other direction. The damper slows this. If you have an rpm that hits a harmonic of the shaft every recoil will be added to each other and if you know anything about resonance, the total force peaks up rather quick (two rotations can double the force, how long will it take to make it 20 times at 3000rpm). Unless you damp each recoil. . .

. . . BTW, some of that recoil is occuring during the power stroke. Literally working against it.

***Edit: To put it simply. . .It's not about the vibrations. It's about the resonance of the vibrations; the sum of them as they pass along the crank.


Who brought silent shafts into the conversation any how? They are different components that serve an entirely different purpose.

***Reedit: ramsack said the exact same thing I said in my edit

 

[ramsack]

-You pull the balance shafts and you can feel a physical vibration in the cabin of your car, which is obviously vibrating your entire motor and say that there are no ill effects? aswell as the BS belt has actual tention on it pulling the crank to the one side.

-You use a solid pully and are worried about the torsional force?
If your that worried, maybe you should make a crank with built in dampers inbetween each bearing.
The bearings are still going to recieve that torsional force and vibrate at that frequency until it reaches the end of the crank anyways, passing through each bearing and twisting the crank.

Reply to your first comment:

The Silent Shafts work to lessen engine movement in more than 1 axis, and they are non-rotational axes.

And to your second comment, you can still get a rebound after the fact of the torsional spike, which is what the damper is damping. It is not to absorb the initial spike of power...That is impossible and would result in less power to the wheels. It's not about the vibrations themselves, but of the interactions of the vibrations hitting other vibrations inside the crank itself, and the timing of them that can create a resonance. When it is at its prime frequency for this the crank will not behave like a solid anymore, but more like a liquid.

Unless you are at a high level of racing you'll never know the difference, and all the people at the highest levels of 4g63 power run a damper. It seems pretty simple to me.

Yeah I'm sure Mitsubishi's thoughts were "let's put a damped pulley on because someone might be making 800whp someday and only then will they need it."

 

[Calan]

Who brought silent shafts into the conversation any how?

That happened in this little golden nugget.

And to your second comment, you can still get a rebound after the fact of the torsional spike, which is what the damper is damping. It is not to absorb the initial spike of power...That is impossible and would result in less power to the wheels. It's not about the vibrations themselves, but of the interactions of the vibrations hitting other vibrations inside the crank itself, and the timing of them that can create a resonance. When it is at its prime frequency for this the crank will not behave like a solid anymore, but more like a liquid.

Extremely well said

 

[tkelly27]

Sounds like a large load of BS to me.

With 30,000 to 50,000 psi of clamp force on the bolts (not to mention the crank sprocket is keyed), I think torsional vibrations would be transferred just fine. If not, then someone better let the Mitsu engineers know, because they used bolts to hold the factory dampener on.

That's what I said. Even if we assume the bolted connection can't transmit force, they pulley is still pinned to the sprocket which is keyed to the crankshaft. Also assuming the pin and the key are not as solid as we'd hope they'd be, they will at least act as a spring and become pre-loaded as soon as the engine starts running. At that point we have 3 degrees of freedom between the outer rim of the pulley and the crankshaft. I forget if you can make an absorber work with that scenario, but I'm pretty sure you can.

Their claim was it was exclusively for damping the belts.

I have a spare block and broken crank, I was going to set something up with weights and a beam hanging from it with degree indicators. One of those projects I need more money to try.

 

[dsm-onster]

That happened in this little golden nugget.

Bah! all just for the sake of arguing . Now we have some poor soul actually believing they are similar in function and purpose.

 

[Calan]

That's what I said. Even if we assume the bolted connection can't transmit force, they pulley is still pinned to the sprocket which is keyed to the crankshaft. Also assuming the pin and the key are not as solid as we'd hope they'd be, they will at least act as a spring and become pre-loaded as soon as the engine starts running. At that point we have 3 degrees of freedom between the outer rim of the pulley and the crankshaft....

Yeah. Sounds like a case of a good salesman trying to sound like he knows what he's talking about.

The clamping force of the bolts provide enough friction that the dampener and crank effectively become one unit. If they didn't, the dampener would slip back and forth in a typical 2-pin/2-hole scenario until the bolts sheared (which wouldn't take long... ask Paul about this. )

 

[Sp1kE]

Lets put dampers on the camshafts. Without one they will turn to liquid and break or wear the cam castles.