Is it advisable to "upgrade" to a lightened crank pulley?

[shinhed]

My SR's totally stock and I fudged my front main seal replacement, chipping the pulley. Is it advisable to deviate from the tried and true stock crank pulley?

[BiG MiKE86]

not unless its an ATI Crank pulley

[shinhed]

SHiiiiiiiiaaaaaaattt
I can buy another s13 for that much$

[burnsauto]

yeah i'd go with a dampaner. prolong the life of your engine instead of gaining 5-10hp

Originally Posted by shinhed

SHiiiiiiiiaaaaaaattt
I can buy another s13 for that much$

welcome to cars, cars cost money.

[shinhed]

Ya don't say?

Stock crank for me. Anyone have one forsale? PM me.

[McRussellPants]

http://phase2motorsports.stores.yaho...sudampusr.html

[J ROK]

So does anyone have anything BAD to say about smaller, lighter crank pulleys? cuz my friend just put one on his motor (not in car).

Is there anything we should be worrying about?

[Pandapants]

^messing up the crank bearings?

[Def]

It deletes the stock harmonic damper(bonded rubber ring), so you'll be increasing torsional vibrations in narrow RPM bands(the crank's natural frequency and its harmonic multiples). This isn't good for bearing life.

[zavala]

the gears for your oil pump in the front cover will most likely break from the horrible harmonics before any real damage is done to bearings. but then after that, no oil=toast motor

[frosti108]

i just got an unorthodox main pulley for the ka. i will let you know if i spin a bearing... i guess lightweight flywheels are advised against as well?

[ayuaddict]

im not sure...

but since the flywheel is just a balanced disc of metal...

it being lighter wouldn't hurt it, as long as its lighter "evenly".

[racepar1]

Originally Posted by shinhed

SHiiiiiiiiaaaaaaattt
I can buy another s13 for that much$

Wow that's a great fucking attitude right there! I guess you'll never put anything but e-gay crap on your car then because it is the only stuff that costs less than the car! Cars cost money, PERIOD! If you cheap out on parts then your car will end up being a horrendous pile of shit with lots of shiny, albeit useless, crap on it. If you want the good shit buy the ATI dampener, it is dyno and race proven to be pretty much the best dampener you can buy. If you are too broke, just get a stock one. If you a little more power, and are broke, then get a solid underdriven pulley. It will cause a bit more engine wear, but I am willing to bet that you will blow up the motor for other reasons before that takes it out.

[illvialuver]

it is true that you do get what you pay for. good luck with the project though.

[JeremyR]

Originally Posted by shinhed

SHiiiiiiiiaaaaaaattt
I can buy another s13 for that much$

you pretty much answered your own question then,
just buy another s13 and swap the pully.

[projectRDM]

I don't know about the SR pulley, but the whole 'harmonics' deal for KAs is complete bullshit that's been passed on for years. The rubber damper in the KA crank pulley separates the A/C portion, it's designed to reduce shock when the compressor is engaged, that's it. People for years removed that front portion and the damper and ran it in SCCA and road events before Unorthodox came out with a lightened version. I ran the UR pulley on my old car for nearly nine years, never had a seal leak, spun bearing, anything. That block is now in my new car, still fine with nearly 190k on it. UR did do a redesign because the early versions wore on the crank seal, they added a steel sleeve right after the first production run to fix it.

[DALAZ_68]

Originally Posted by racepar1

Wow that's a great fucking attitude right there! I guess you'll never put anything but e-gay crap on your car then because it is the only stuff that costs less than the car! Cars cost money, PERIOD! If you cheap out on parts then your car will end up being a horrendous pile of shit with lots of shiny, albeit useless, crap on it. If you want the good shit buy the ATI dampener, it is dyno and race proven to be pretty much the best dampener you can buy. If you are too broke, just get a stock one. If you a little more power, and are broke, then get a solid underdriven pulley. It will cause a bit more engine wear, but I am willing to bet that you will blow up the motor for other reasons before that takes it out.

wowzers

[shinhed]

Originally Posted by xdarkrune

you pretty much answered your own question then,
just buy another s13 and swap the pully.

I don't no where you buy your $500 240's, but around here they don't come with Sr's to harvest pulleys

Originally Posted by racepar1

Wow that's a great fucking attitude right there! I guess you'll never put anything but e-gay crap on your car then because it is the only stuff that costs less than the car! Cars cost money, PERIOD! If you cheap out on parts then your car will end up being a horrendous pile of shit with lots of shiny, albeit useless, crap on it. If you want the good shit buy the ATI dampener, it is dyno and race proven to be pretty much the best dampener you can buy. If you are too broke, just get a stock one. If you a little more power, and are broke, then get a solid underdriven pulley. It will cause a bit more engine wear, but I am willing to bet that you will blow up the motor for other reasons before that takes it out.

There was no attitude with my reply, only sticker shock. A guy's gotta eat before dropping $500 on a magical pulley.

Please believe I researched the ATI pulley after seeing that price and at the moment it's a no go. I'll stay stock.

P.S
There no "eGay" on my cars

Originally Posted by illvialuver

it is true that you do get what you pay for. good luck with the project though.

Most definately.

[kandyflip445]

Originally Posted by projectRDM

I don't know about the SR pulley, but the whole 'harmonics' deal for KAs is complete bullshit that's been passed on for years. The rubber damper in the KA crank pulley separates the A/C portion, it's designed to reduce shock when the compressor is engaged, that's it. People for years removed that front portion and the damper and ran it in SCCA and road events before Unorthodox came out with a lightened version. I ran the UR pulley on my old car for nearly nine years, never had a seal leak, spun bearing, anything. That block is now in my new car, still fine with nearly 190k on it. UR did do a redesign because the early versions wore on the crank seal, they added a steel sleeve right after the first production run to fix it.

Werd. My KA has over 210k and I've had my pulley for over 50k.

Dunno about the SR.

[burnsauto]

Originally Posted by projectRDM

I don't know about the SR pulley, but the whole 'harmonics' deal for KAs is complete bullshit that's been passed on for years. The rubber damper in the KA crank pulley separates the A/C portion, it's designed to reduce shock when the compressor is engaged, that's it. People for years removed that front portion and the damper and ran it in SCCA and road events before Unorthodox came out with a lightened version. I ran the UR pulley on my old car for nearly nine years, never had a seal leak, spun bearing, anything. That block is now in my new car, still fine with nearly 190k on it. UR did do a redesign because the early versions wore on the crank seal, they added a steel sleeve right after the first production run to fix it.

true, its not going to grenade your engine most of the time. Im not putting down an aluminum pulley either...they def. have their advantages, I'd just rather put them on a balanced crank. Dampeners only really have a useful advantage at higher rpm's.. so it'd make more sense to have it on an sr than a ka. (not saying the ka CANT rev as high... but for the majority, most ka's don't.)

[!Zar!]

The whole harmonics thing is true for muscle cars and what not, but most euro cars and over seas cars, no.

[Def]

Originally Posted by projectRDM

I don't know about the SR pulley, but the whole 'harmonics' deal for KAs is complete bullshit that's been passed on for years. The rubber damper in the KA crank pulley separates the A/C portion, it's designed to reduce shock when the compressor is engaged, that's it. People for years removed that front portion and the damper and ran it in SCCA and road events before Unorthodox came out with a lightened version. I ran the UR pulley on my old car for nearly nine years, never had a seal leak, spun bearing, anything. That block is now in my new car, still fine with nearly 190k on it. UR did do a redesign because the early versions wore on the crank seal, they added a steel sleeve right after the first production run to fix it.

Sorry Russ, but you're wrong on this one. That bonded piece of rubber and the AC ring is there because they are targeting a specific frequency and that piece provided the right spring constant and inertia to meet that frequency. IIRC, the equation is frequency = sqrt(Inertia)/k, where k is the spring constant of the rubber portion.


Now as far as engines being fine, I have no idea where the natural frequency of the stock crank is, but it might be above the stock redline, which can frequently happen with short/stiff 4 cylinder cranks. I'm still of the opinion that there are easier ways to make power with these engines that aren't as "risky" as this, because you know SOMEWHERE you are getting a HUGE amount more vibrations. Otherwise I'd think the factory wouldn't bother.


Here's an illustration of a 2nd order mechanical system, the middle one is what happens when you have a properly designed dynamic vibration absorber(i.e. a stock crank pulley):

[Def]

Originally Posted by !Zar!

The whole harmonics thing is true for muscle cars and what not, but most euro cars and over seas cars, no.

You could easily hear the crank on my first E36 M3 "ring" after I put on a UR pulley at the stamped natural frequency of the damper(about 3.6k RPM). I knew what the dangers were, and it was harder to make power with those engines back then. I don't think I'd put one on today. It made about 12 rwhp, so a pretty big difference on that motor, but obviously it's because the stock damper works overtime with a long I6 crank whipping around.

[UNISA JECS]

The best thing you can do is make sure the pulley is balanced if its a lightened aftermarket pulley, to me the lighter the less effect teh pulley shoudl have on harmonics if it is balanced. But between the KA and SR, the SR should be better suited to deal with harmonics because the crankshaft is fully counterweighted whereas the KA is only half counterweighted.

[Def]

Originally Posted by UNISA JECS

The best thing you can do is make sure the pulley is balanced if its a lightened aftermarket pulley, to me the lighter the less effect teh pulley shoudl have on harmonics if it is balanced. But between the KA and SR, the SR should be better suited to deal with harmonics because the crankshaft is fully counterweighted whereas the KA is only half counterweighted.

Lightness has nothing to do with it. This vibration is a result of an imbalance in the rotating assembly, it's the crank's natural frequency when being subjected to power strokes. Just like a tuning fork vibrates, so will your crank when excited at this natural frequency.

[projectRDM]

Originally Posted by Def

Sorry Russ, but you're wrong on this one. That bonded piece of rubber and the AC ring is there because they are targeting a specific frequency and that piece provided the right spring constant and inertia to meet that frequency. IIRC, the equation is frequency = sqrt(Inertia)/k, where k is the spring constant of the rubber portion.


Now as far as engines being fine, I have no idea where the natural frequency of the stock crank is, but it might be above the stock redline, which can frequently happen with short/stiff 4 cylinder cranks. I'm still of the opinion that there are easier ways to make power with these engines that aren't as "risky" as this, because you know SOMEWHERE you are getting a HUGE amount more vibrations. Otherwise I'd think the factory wouldn't bother.


Here's an illustration of a 2nd order mechanical system, the middle one is what happens when you have a properly designed dynamic vibration absorber(i.e. a stock crank pulley):

I won't disagree because there may be truth to that in some cases, but I've seen a lot of import cars not equipped with factory A/C (not Nissans though, but still) that do not have any kind of damper in the pulley. The KA is particularly prone to NVH anyway, I've worked on cars where accessory bolts were loose or missing, but I've never seen/heard any issues from running a lightened pulley other than oil leaks from the seal on lesser designed copies. I'd like to think after over a dozen years I would have come across a broken crank or bearing damage somewhere if it was a definite possibility. My car also had an aluminum flywheel for a portion of it's life, again no issues, no weird vibrations, no loose bolts or torn mounts. It actually idled and revved smoother with the lighter components.

On your BMW with a long ass crank I'd suspect there'd be way more harmonics in place. Same goes for any V8 engine. On a 4cyl like a KA that's only half counterweighted you're not introducing any more resonance than you would anywhere else. I still stand behind that, but as there are numerous things that people question (banjo vs. flare brake lines for example) I'm not going to put a life on it. Modifying a car in any way will always increase the risk of failure, especially when pushed harder than normal. You run the risk of damage with even an air intake if you really think about it, but the pros outweigh the cons all day long.

[Def]

It might be fine on these cars, or one of those things where the natural frequency is so narrow and high that you just briefly cross it and don't get many torsional vibrations.

As for a lightweight flywheel, I've read that it changes the natural frequency that the crank will bend/twist at, and I've read it doesn't. It makes sense that it would change it, but it's not removing the damper, so essentially zero worry there, as you'll still likely not have a large spike in vibrations/twisting at a given RPM.

[Def]

BTW - some other applications of a dynamic vibration absorber is when they suspend the AC units in a large skyscraper in a cradle held by a specific spring rate spring. The AC unit will rock back and forth at the same frequency the building wants to sway in heavy wind, thus damping the movement at its natural frequency.

Some high end bows(like bow and arrows) have these little flexible rods coming off them that vibrate like an MFer after you fire it, in effect countering the vibration of the bow frame itself.


I do think solid crank pulleys are a reason why the RB guys eat oil pumps for breakfast so often. They are now starting to learn that a crankshaft damper is a good thing, and are going for ATI stuff.

[projectRDM]

Originally Posted by Def

I do think solid crank pulleys are a reason why the RB guys eat oil pumps for breakfast so often. They are now starting to learn that a crankshaft damper is a good thing, and are going for ATI stuff.

Another good example, an RB has a long ass crank and is fully balanced. Changing the pulley would make a difference.

[zavala]

i just remember reading a thread on freshalloy about someone blowing up the gears in thier new oil pump and had no clue why. about halfway through the thread someone asked about what crank pulley he was using and it turned out to be some lightweight aftermarket piece. many big names said they to had, had many other oil pumps go bad because of the "lightwieght pulleys". not worth the risk in the end to me to gain a little power.

here, have a read.
http://forums2.freshalloy.com/showth...light=oil+pump