Dubi, thank you for the question. I did not mean to imply that I don't know what a harmonic balancer is. I am not perfect and I must have misunderstood his point.

I have left my experience out of this because it's of no consequence. I will say that I have over a decade of experience with these cars... but don't mean to imply that I'm an expert in any way.

Your question is exactly what I've been wanting to talk about! Instead we got stuck re-hashing old points... but I digress. The Mitsubishi designers (of this style silencers) claim that that by reducing the frequency, it helped accessories among other things last longer. Since it is harsher at higher engine speeds, wouldn't racers benefit most from them??

 

This was the original post.

From experience many of us, particularly those who race these cars and subject them to higher rpm know that the vibration is real, and worse, without balance shafts and generally cause engine parts to come loose and things like oil pickups to break . But you seem to disagree.

Your first response suggested you do not accept that the vibrations are worse without the balance shafts. The remainder of your posts seem concerned with arguing that the purpose of the balance shafts is to reduce noise in the cabin and that the idea they actually reduce real vibration in the engine and stop things loosening and breaking is a bit of fiction. It's not.

 

Great point, and it is confusing, let me clear that right up! The initial design of the shafts are to reduce interior noise of the cabin, but it turned out that sound can also resonate certain other parts of the car too... this is said to increase the life of engine components, but remember that I'm referring to the sound, not the actual engine vibration...

 

lol

 

If there is no actual vibration, how does the sound resonating other parts of the engine cause them to break?

 

The sound is apparently amplified and vibrates... this is the words of the designers.

I am in no way saying this is fact, it sounds bizarre to me too, but this is what they said, so don't shoot me!

I'm just having a conversation...

 

So how is this vibration cause by amplified sound different from the engine vibration we have been talking about all along?

 

I think it would be more accurate to say that the vibration causes the sound, not the other way around.

 

Sound can be counteracted by another sound from the car stereo, this for instance:

 

The sounds my car makes are so loud I can't hear anything anymore

 

Ultimate sound of Metal!

 

So.. Than how about the harmonic balancer on the 968/S2 crankshaft.. How does that come into picture?.. Is that meant to cancel out sound as well?

 

apparently the parts break because small elves are beating on them with hammers in a futile attempt to change the resonate frequency after reading on the internet that the resonate frequency could be changed by hitting things....this is now know as the edredas effect.

In order to keep my sanity while reading some of this I have started to add the phrase "once upon a time in a land far, far way" to the beginning of some posts, that seems to make the rest of the content make more relevant.


Seriously - there has been more inaccurate information about balance shafts in this one thread that all others I have seen to date combined. Read on at your own risk!!!

 

The noise from my supercharger must really mess with those elves. I wonder what resonance it causes spinning at 80,000rpm!

Chris, on a serious note I was interested in this comment.

I am generally spinning my engine up to 7500rpm but occasionally it will go to 7800 or so if I hold a gear for some reason. Have you seen evidence of balance shaft bearings failing in high rpm use? Is there anything that can be done to reduce risks of that type of failure when balance shafts are retained in high rpm usage, such as any type of block preparation or particular attention in assembly?

 

Sorry, it is my mistake. I figured that since this was a large forum that there would be actual engineers here that wanted to discuss this for real.