The simple answer may be this:

 

My biggest gripe with removing the balance shafts is that you're removing a component designed to minimize vibration. Vibration causes accelerated wear on components. How much is up to debate, but if you can feel the NVH from removing the shafts, your components can too. Comparing to solid engine mounts is an unfair comparison, as we're talking about minimizing internal engine vibration, not just minimizing the transfer of harmonics to the chassis(the whole point of rubber engine mounts as opposed to solid ones).

 

The fluidampr helps in reducing torsional vibration in the crankshaft, I believe this is different from the purpose of balance shafts, in that they are designed to reduce 2nd order vibration.

 

my point with the mounts was that the engine is vibrating regardless of if you are feeling it or not. The forces that are acting on the engine that create the vibrations are there regardless if you feel them or not. The imbalance remains even with the shafts, they are just masking it for your comfort. If your the crankshaft, you are feeling those imbalances regardless of the shaft spinning next to you.

 

FWIW I was in the 'keep your BS' camp before this thread and I've come around since having read through it. Next time I've got the block out I'll be removing them. Thank you all for having the conversation.

 

My opinion is this is more useful on the other end (flywheel) because of the short fistance between #4 and flywheel, mainly to help with #4 oil journal cracking issues. I know many don't agree, but that's my opinion.

 

Sorry, see post #63.

 

Please present facts to support the argument the removing the balance shafts allows the 2nd order vibrations to damage components. There is plenty of evidence to show that it doesn't.

 

https://www.ijser.org/researchpaper/...-Isolation.pdf

"Vibrations in an engine are undesired since they can cause increased stresses, added wear, increased sound levels, material fatigue, energy losses and increased bearing loads. This can in time lead to mechanical failure and breakdown."

Still having trouble wrapping my head around how removing something designed to reduce engine vibration has no effect on reliability. This paper goes into detail on engine vibrations and their effects, perhaps it's worth a read.
For a race motor that isn't expected to have a long life, I totally agree this is not an area of concern and the added complexity of a balance shaft system is more of a hindrance than a benefit. However let's keep in mind that most average people who want to enjoy their car aren't looking to break horsepower records and just want a reliable motor. I think one of the issues is that people are under the impression that the balance shafts simply mask the vibration. This is not the case, they are designed to cancel out the vibration through an equal opposing vibration. Two opposing sines will cancel eachother out, not just hide each other.

Further info from that same paper:
"It can be summarized that vibrations in a machine or an engine are the undesired part since they can cause increased stresses, added wear, increased sound levels, material fatigue, energy losses and increased bearing loads. These can in-time lead to mechanical failure and breakdown. Vibration reduction clearly improved engine efficiency, as well as reduced breakdown costs is the greatest benefits. The best solution to a vibration problem is to avoid it in the first stage that is at the time of design. Therefore it is important to design the engine such that none of these vibrations are close the natural frequency of the engine. If the vibrations of the running engine are close to its natural frequency, they will amplify each other and generates higher forces and causes early breakdown of the bell housing or other engine components. "

Perhaps a better argument to make is that the balance shafts don't reduce vibration as much as one would think, but to say vibration has no effect on components is completely incorrect.

 

This article is referring to first order vibration and torsional whip. When have you seen an evo fail a bellhousing due to fatigue from vibration after deleting the bashafts? Oh, it doesn't happen...

That paper was about a 6cylinder diesel and engine mounts. This is why I drink.

Next...

 

So are you saying 2nd order vibration has no effect on components? Because that seems to me the point you're trying to prove.

 

Perhaps this one is worth a read as it specifically relates to balance shafts, albeit in an inline 4 diesel.
https://www.researchgate.net/publica..._Diesel_Engine

After reading through these papers, I can agree that the primary purpose of balancing out 2nd order vibrations is driver comfort, however they all state that these vibrations will also add to component wear. There has been no in-depth analysis of the magnitude of wear components will experience, I am still on the hunt for some solid tests and data on that subject.

Also found this info which supports the BS delete claims, however haven't found anything solid to back it up.
"One might think that the balance shafts would help the rotating assembly be more balanced. However, the balance shafts are independent of the rotating assembly. Any secondary vibration in the rotating assembly first gets absorbed by the main bearings, transferred to and then cancelled in the block by the balance shafts. So in terms of minimizing bearing load, the balance shafts don’t have any benefit. As such, it seems almost necessary to remove the balance shafts for a performance build."

I'm all for believing that a BS delete will have no effect on reliability, but I don't want to assume that because some people on the internet said it is so without providing any real data behind their claims. I hope you all can understand that.

 

Holy crap, this thread. Why is an old subject, that's been handled, being brought up again, in the exact same way? Who here is guilty of too much free time??

So we're second-guessing Mitsu engineers and bean counters, after the fact?

Or religion. "Prove to me God DOESN'T exist" makes about as much sense and "prove removing BSs doesn't damage an engine". You can have someone prove something. That's easy. Having them prove lack of something is a good way to keep someone from winning an argument.

This thread is LOLz, though. I enjoy reading. Next, can we discuss the merit of tube televisions? Maybe there is something they've left on the table

But seriously. Carry on, please

 

If you're going to make a claim like "removing balance shafts has no effect on long term reliability" I expect some proof or at least some explanation behind that statement. All I've heard so far is "it doesn't and you're wrong if you think otherwise". I'm all for deleting them, but I'd like to see some harder evidence about possible negative effects. I'm totally open to these guys being correct but I don't want to believe they're correct simply because they say so, hence the thread for discussion.
Unfortunately I feel as though people care more about being correct than actually sharing knowledge.

 

There is proof all around you: years of engines running without, with no negative consequences. If someone wants facts or figures, instead of real world evidence, then good luck because, like I said: nobody does studies to prove something doesn't happen. That just makes no sense. There is no such thing. That's not how evidenced-based practice works.
What you have:
Lack of evidence that deleting balance shafts negatively affects an engine.
What you want:
Evidence that balance shafts cause no negative side effects.

That's not how it works. .