NewShockerGuy

iTrader: (1)

I was browsing some sites, for parts that I want to later upgrade...

Came across the Crank pulley. I have been doing research and I do NOT want to get undrive pulleys for many many things that I have heard that make them bad... even though I know a lot of people use them, I am not. Instead I found this: The Autospeed Performance Crank pulley. It's 1.5 lbs and it's the same size as the stock pulley in the car, but it's hollowed out..etc.. Only problem I read was that is does not have aharmonic dampener...

Here is a direct quote from fastwrx. "Note: The factory crank pulley incorporates a harmonic dampener, and the billet aluminum pulley does not. Removing the harmonic dampener may have an effect on the lifespan of the engine."

I have no clue what this means? Nor do I know what it does?


From reading that, it gives me second thoughts on wanting to buy one of these and have it put on to give me some more power... I really don't want to kill the life of my engine, but is it true that anything you do.. IE exhaust things that make MORE power from your engine are in time stressing it and making the lifespan shorter?

Thanks,
-Nigel

ish

iTrader: (7)

i'll give you a real quick answer because i am tired and want to go to bed, without the harmonic dampner your engine would vibrate a lot more and hence reduce the life span

NewShockerGuy

iTrader: (1)

hmmm...

Would STI engine mounts fix that? If not then this probably would would not be a good upgrade to get more power if it's going to shake your engine to death...


Thanks,
-Nigel

andyhidley

There are vibrations that happen at certian frequencys in your engine. These can become destructive. What the dampener does is dampen the oscelliations when they occur at a given frequency. Without the dampener you run the risk of breaking your crankshaft. That could happen due to the harmonics generated in your engine. It depends if you happen to run your engine at that frequency very often . Doing it many times and for any length of time will weaken the crank.

Maybe this is a better example.... If you drove your car without shocks then the wheels would be going up and down all the time wearing out every suspension part till they failed. Put shocks on and it oscellates less and will last longer. You need something to absorb the vibration........

NewShockerGuy

iTrader: (1)

Hmmm..

Good example! Now I don't want to get this because I don't want my crankshaft breaking. Seems pretty stupid why parts are made if your engine could die because of it...

yuck!


Thanks,
-Nigel

andyhidley

Well its not gonna explode after 100 miles.. Every crank is different and has stresses and weaknesses in different places and is subjected to different loads and vibrations.

It may never break. But I would say with 99.9% certinanty that it wont when the harmonic balancer is on.....

I had a 1963 Chevy 283 Cubic inch V8 that came from the factory WITHOUT a harmonic balancer. The motor melted a piston at 170,000 from the previous owner. So I really bought a V7 *L* I planned on rebuilding it anyway and put it in my 1969 camaro. I worked the motor over pretty good , it made a respectable 275 HP. And I put another 160,000 on it before I sold it. I only bored it once, (0.030) and ran it everyday. It NEVER broke its crank.. But It was a forged crank from the factory.

I personally dont have a smaller pulley on my car. If i were to get one I would be more worried about killing the battery. See batterys can only "cycle" so many times till they are shot. smaller pulleys=lower alternator RPMs So when sitting at a light ideling with the headlights on, fan, yada, yada you'll be pullin from the battery. It will only shorten its life alittle. But thats just my preferance.

Kostamojen

iTrader: (2)

In case anyone doesnt know, the stock crank pulleys on early model Imprezas DID NOT have harmonic dampeners. This leads me to believe that its more or less there for keeping the engine quiet rather than actually increasing the life of the engine (As there are quite a few early model Imprezas running around on engines with 200,000+ miles) especially since the inherant design of a boxer engine does not require the use of harmonic dampeners or things of that sort.

andyhidley

"especially since the inherant design of a boxer engine does not require the use of harmonic dampeners or things of that sort."

Its the inherint resonate frequencys created by the engine.

1-Also do the "early model imprezas" have forged cranks?
2-do they "early model imprezas" operate in the same RPM range as new WRXs? (frequencys are generated via RPMs
3-Does the the "early model imprezas" have the same stroke as the WRXs
There are dozens of other factors that come into play that can create distructive vibrations.

Kostamojen

iTrader: (2)

1. I dont think any USDM engine has a forged crankshaft.
2. 6000rpms
3. EJ18 Bore x stroke = 3.46 x 2.95, EJ22 Bore x stroke = 3.82 x 2.95

But what Im wondering is what kind of damage you would see from "distructive vibrations". Most subie engines that have died have died from either blowing themselves up from too much boost or from gasket failures, but I dont see too many pre-mature engine deaths with subie engines related to bad frequency vibrations.

SubySal

Think of it this way. If you hit a high enough note for a glass it can shatter right. The reason this happens is the individual molecules start to move around independently breaking the common bond they all have to form the glass. The glass then breaks into the individual or more likely groups of molecules(broken pieces of glass). This happens only at a certain note or frequency. Molecules are always moving the frequency wave just excites them and causes them to move more. Now before a glass shatters it develops cracks right the same thing can happen to steel or aluminum.

Now hypothetically speaking lets say the note for shattering the crank is the harmonic signal produced at 5467.3 RPM and for the aluminum head 5834.7 RPM. Now depending on the amount of time you spend on the specific rpm is what determines the effect it will have on said parts. It won't shatter the part, but harmonics can develop microfractures in the crank or other metal parts which can lead to it failing. Fractures are caused by a group of molecules getting so excited they break that common bond.
And by the way different metals have different densities so they will excite at different frequencies.

Also harmonic balancers are for harmonics not vibration. Here's the difference. Take a flat tire it goes around making the thump-thump sound and you can feel it in side the car right. Lets say you feel a thump twice per second at the given speed your going, giving it the frequency of 2 hertz. Now if you've ever gotten shocked from an outlet you would think it was constant right, but in fact AC voltage cycles between positive and negative 60 times a second or 60 hertz. To a person it happens so many times a second it just feels constant.
Vibration you can feel i.e. rough idle, Harmonics you can't feel at least not with everything else going on in a car while driving or even idling. Even 60 hertz can be somewhat felt or more likley heard such as the buzzing from flouresent lights. If you could count fast enough that buzz would occur 60 times a second.

Now back to the Harmonic balancer. I'm not sure which way it works exactly , but its purpose is to cancel out the harmonics caused by the motor by absorbing the harmonics or dampening them. Usually harmonics are caused by pistons and other engine parts going up and down or cycling at angles other then 180 degrees which is why some companies (eg. Nissan and Mitsubishi) use "silence shafts" They send out a wave in the opposite direction of the wave caused by say a piston coming down or going up to cancel it out since they use inline or "V" configurations. The flat engines are the exeption. Since the pistons are opposed and travel in exact opposite directions (180 degrees) at the same speed at the same time they cancel each other out so the only harmonics that can be produced would be minimal. Possibly by valves opening and closing and other engine parts cycling back and forth.

Last analogy I swear, but it might make it a little easier. You throw a rock into a pond then at a right angle you throw another rock identical to the first one with the same force and everything. the waves they create will cross at a 90 degree angle join together and continue at a 45 degree angle. Do the same thing with a 180 degree angle and with the waves coming in from opposite directions they will just stop where they meet canceling each other out.
OK that's, it I'm spent! Hope this helps or at least doesn't cause any more confusion.

andyhidley

SubySal.. Explained it very well...
So the bottom line is that your motor wont explode, but the crank "may" break.

NewShockerGuy

iTrader: (1)

Thanks for the replies!

Kinda sad because they said this would increase hp of about 5 or so... that's not too bad... But I'm not going to take the chance and have my crankshaft break....


-Nigel

Kostamojen

iTrader: (2)

Lightweight pulley gains are mostly in 1rst-3rd gear, and do make a difference IMHO. Its like having a somewhat lighter flywheel that doesnt cost nearly as much as an actual lightweight flywheel (unless you go for the whole pulley set)

SubySal

Thanks for the compliment Andyhidley.

Personally though I want to go with a lightened billet steel flywheel eventually.