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Originally Posted by driftartist
I understand why that would make sense, but thats not what rebello racing in the ca bay area says. and while a boxer engine has considerably less vibration and torsion, it is still possible to do damage over time. You are correct on the inline engines but it still applies to the boxer as well.
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It seems to an issue that should be fairly easy to determine.
I haven't seen/read much about older Subarus grenading their engines (and lightweight pulleys have been around for a long time).
I had free time on my hands, so I took a look around (good research anyways, as I still have my crank pulley from my BRZ - in case I get another one down the road):
http://forums.nasioc.com/forums/show...5&postcount=13
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I did more search trying to see for myself that the aftremarket lightened crank pulley really does damage to our boxer engines. I found nothing to prove that and instead i came across this post by Subaru Rep. He said...
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According to the tech guys at SOA the boxer engine balances itself WITHOUT the aid of ANY form of dampener.
The pistons counter-balance the engine.
This is also helped by the fact that the crank uses 5 main bearings just like most other engines do except that our crank is about 1/2 the size of thiers so its able to withstand around 10 tons of preasure at any given point.
The main reason for a dampener is to help prevent crank walk and since the engine does not have to fight gravity in its running cycle there is no crank walk and hence no need for a dampening system.
I also found some posts by manufacturers (Vishnu, Unorthodox racing, etc...) discussing these lightened pulleys and they all back up what is said above. It was basically pointed out that stock crank pulley for Subaru is plainly just a crank pulley...not a Harmonic Balancer as also pointed out by SOA itself!
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http://www.ft86club.com/forums/showp...94&postcount=9
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Interesting info.
This comment from the above is also enlightening (pun intended?):
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Scooby921 Thursday, September 03, 2015 5:13 PM
As a former design engineer for crankshaft dampers I just wanted to point out a couple important items.
The crankshaft damper has nothing to do with engine balance and vibrations. Motion and oscillation of the powertrain, as an assembly, is addressed by your engine mounts, transmission mounts, and potentially roll restrictors.
The purpose of a crankshaft damper is to reduce the angular twist / deflection of the crankshaft. Combustion creates pressure. Pressure becomes load into the connecting rod which creates torque on the crankshaft. That torque creates deflection of the shaft as it's not infinitely stiff. Depending on the material, journal offset, length of the shaft, and loads created in the cylinders you can see several degrees of angular deflection in the crankshaft. I've seen an OEM crankshaft which displayed 7° of deflection without a damper. With the damper it was under 2°.
The mass of the crank damper and the stiffness of the spring element (the rubber part) are vital to the effectiveness of the damper. They control the resonant frequency of the damper and impact the effective damping. If you change the mass or change the spring stiffness you change the frequency at which it operates. If you don't have enough mass, even at the correct frequency, you don't provide sufficient damping. An incorrectly tuned damper could actually make things worse.
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Two seemingly-different conclusions from what appear to be credible sources.
I guess it's one of those "do it if you're comfortable" mods.