"Just because it is there doesn't mean it is needed. There are too many design parameters for the engineers to consider other than longevity and performance to make that blanket statement."

What you said in your statement before this one makes perfect sence. The problem I have with this one statement is this...

Engineers don't do things for no specific reason, It's there for a REASON. Otherwise why are they wasting the money? Making something 5.5-lbs costs more than making something thats 1-lb. There had to be some reason, not just a blanket statement, they did it because they did it type thing.

I'm sure your right though and i'm not saying it, I'm uniformed and am happy to say that, I'm asking questions because I DON'T UNDERSTAND. Engineering wise the damper is there for a specific reason.

 

It's a statistical thing. Not every car will explode without a balancer but some will due to an unlucky combination of tolerances that produces resonant harmonics... leading to vibration induced metal fatigue, increased wear, or a bolt loosening somewhere. I believe that bean counters at the car manufacturers have very carefully weighed the couple dollars per car it costs them to outfit balancers against the expected warranty claims within the 36,000-50,000 miles they'll cover the cars for. And they decided to spend the money.

General Motors is most famous for penny-pinching engineering, and even they used balancers on pretty much everything that spun over 4000rpm. The low-revving V8 engines that did not come so equipped all had cast cranks... those internally damp vibration better than forged cranks which "ring" and efficiently transfer vibration elsewhere. (In those olden days the distributor was driven off the camshaft and uncontrolled vibration there caused timing to fluctuate wildly; a phenomenon known as "spark scatter." Engines without dampers were known to wear their timing chains faster and experienced this sooner... usually *just* out of warranty. Damn those bean counters are good.) Every 18-wheeler is also equipped with a balancer even though those engines do not go over 2000rpm; but then those are designed to give over 500,000 miles of service.

Accessories cause vibration, which is why most modern engines now have them solidly bolted close to the engine instead of using vibration-amplifying brackets anymore. Without a damper, those supercharger pulsations will be transmitted all the way through the engine to the flywheel before being damped. Which brings up an interesting point--each damper design operates best at a particular frequency and amplitude, so if the engine is modified to operate outside those limits, the factory damper may no longer do anything. Harmonic dampers do the same job as shock absorbers, and we know those are not all equivalent either.

 

=0)

 

Flyin':if you can reach this guy, he might have an opinion; his forum is closed but his site is open and he may be e-mailable. Larry is the man and has built many four bangers.

www.theoldone.com

 

I'm not getting the underlined portion, are you talking about the damper in the crank pulley or something else? I mean this seriously since others on here have been being sarcastically negative about everything.
Will you please clarify what you mean. I think you have great info I could not understand it. By I-6 did you mean 1.6? In other words please elaborate.
I'm glad that we actually have some additions that are something besides flaming, it's gets annoying when you have a bunch of people that have no scientific or physical evidence of a need or non need of something and try to battle it out with words. I really think everyone on here needs to give an apology, i have lost alot of respect for some of you, and in my opinion if everyone, including me, weren't acting like children, the moderators wouldn't be needed. So I will deliver my apology right now, I HOPE OTHERS WILL FOLLOW!

I'm sorry if I have offended, degraded, flamed, owned, and/or upset anyone in any of my posts in this thread.

Thank You

Mike aka "Chili"

 

Yes, and supercharged cars with a Gilmer (cogged) belt drive will actually break things right now without a crank pulley damper. The generated torsional forces have to go somewhere to be dissipated, and that somewhere is the flywheel at the back of the engine where they are absorbed. In the meantime the whole crank is twisting back and forth like an oscillating spring from the loads imposed by the cam drive, accessories and supercharger on the front. It's hard for some to understand how such relatively small vibrations can be so destructive when there are also really strong power pulses (combustion events) going on, but it's the high frequency and constructive interference at particular rpms that does it.

The Tritec may well have been engineered to avoid these constructive frequencies (at least in stock form) and prevent bolts from working loose even without a balancer (though there are a bunch of threads where people complain their lightweight pulley bolt keeps loosening up) but BMW didn't want to gamble. I guess everything can be summed up by Clint Eastwood as... "well do ya feel lucky, punk?" Do ya?

 

So... what? Are you saying the dampened pulley that is stock on the car is good, bad, or indifferent?

 

Hey Mike, I6 means an inline 6 cylinder engine, ala BMW 6. So he's referring to the length of the crank for an inline 6 versus an I4, or inline 4 like we have in our MINI's.

 

I'm saying it must be matched to the vibrations it will encounter to work. BMW engineers probably matched it pretty well to the engine in stock form.

It's the same as saying stock shocks don't work well with race springs, but work fine with the stock springs they were designed for.

Previous discussion here: https://www.northamericanmotoring.co...d.php?t=46574&

 

Read posts #53-70 on this thread: https://www.northamericanmotoring.co...t+crank+pulley
There is more thank enough meat there to address this question, including 'The Word' from a Tritec engineer.

P.S. Pay particular attention to post #69. :smile:

 

I always wanted to be a member!

Matt

 

we will let you in on the heisenberg principle

 

I've modified my car to where the stock crank is no longer working as intended for the stock engine. From my calculations, I now need crank pulley that is 2% larger, and about 87.5% lighter in order dampen properly, with my mods.

The number crunching was intense... it covered the back of several envelopes... which are now in the Buck Stove, unfortunately.

 

That you can know either when or where the meetings are, but not both!

Matt

 

we all know that the math was to prove to your wife that getting the Alta pully really is better than paying the cable bill!

And the crank not working as intended in the motor? What, is it going in and out instead of round and round?

Matt

 

Can you share the mods you have done to get to this point?

 

I had an alta 2% on my car until I threw a rod through my block. Not sure if it was from the pulley but I did loose an engine.

 

Did you calculate in the pulsating renascences the supercharger imparts to the shaft and pulley?

I wonder if there really isn't more evidence but it has yet to be revealed i.e. pulleys walking off, belts breaking.
A couple of indicators possible would be, oil analysis at regular intervals to see if bearings are showing wear earlier. Or a vibration frequency monitor on the engine block like a knock sensor to log changes with and without the solid pulley.

 

Is anyone performing a post mortem tear down to determine the cause?

 

That's the second post from you on this with no real info - can you please elaborate? Were you running a 19% pulley? How many miles on the motor? Any oiling issues? Any water involved? etc?

I'd also like to see pics of the block and the subsequent teardown - I love post accident analysis!

Thanks!
Randy

 

I haven't, I was being cynical because my engine hasn't self-destructed yet.

 

since install! (pulley)
any werd from this guy yet?

 

I was able to purchase a used one from Randy Webb after he replaced it with one of the Alta units. Eric at Helix or one of the other vendors may have some on hand as well.

 

This should be fairly obvious, but the recollection of one unofficial casual telephone conversation with one engineer doesn't mean diddley-poop as to the need for a damper on a crankshaft pulley.

Apparently BMW's engineers didn't have the same conversation, since they chose to build a vibration damper into their version of the pulley.

IMHO, BFG9000's comments are one of the few rational comments on this topic in the past two days:

 

Why? Do you have a problem trusting the people that designed the engine?