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Balance shafts

tektic

Well-known member
Joined
Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
Someone I know was telling me that the evo 9 shafts are the lightest because someone told him. I don't know anything about it. If they even fit a 6 bolt motor... I just don't know.

We have all seen This page from jack
Jack makes a case for keeping balance shafts... his reasoning however might as well been IDK they are magic I think.

After reading This Artical though I'm starting to turn the corner on The idea fo keeping them in place. The line that states "The rolling couple of a balanced four-cylinder engine, with this arrangement provides
a better result than that of a six-cylinder unit." realy hit home.

So Lets say I wanted to install Balance shafts in my next build. If everything in that engine was balanced and lightened shouldn't the same be done with the balance shafts? Is it possible to make sure the two I have, have the same counter weight?
 

slugsgomoo

Well-known member
Joined
Oct 16, 2003
Messages
3,776
Location
Tacoma, WA
There's a thread on dsmtalk where Jack finally admits that he's wrong due to his fact-free conjecture, but still won't remove his bad info from his stupid website.

Mitsubishi doesn't put the balance shafts in some Sirius motors from the factory, and their engineers are vastly smarter than Jack.

Since this link to an old post may or may not work...

Quoting slugsgomoo:
Quoting presterone:
So light weight flywheel and no balance shafts = super duper torsional whip of crankshafts. Im sure people have ran thousands of miles with no issues with a lightened wheel and no balance shafts but doesn't it seem sketchy on paper?



I see you've read Jack's poor conclusions about crank vibrations... Here's my response to a similar post on the friendfaces...

Quote:

it's the one place that I will categorically say that Jack's is wrong, and I think they're great otherwise.

Fact: Mitsubishi built dozens of 4gxx motors that came from the factory without balance shafts. If the motor can't live without them, wouldn't Mitsubishi's engineers be able to figure that out? Let's assume that some of them have a Masters in Mechanical Engineering (or better) and have an idea how torsional & harmonic damping work

Fact: The documentation from Mitsubishi says that the shafts are there to increase occupant comfort by reducing felt vibration from ~3-5k RPM. Felt vibration means your ass is happy, it has nothing to do with the mechanicals.

Fact: Even if replaced regularly, the balance shaft belt is very small, and spins a very heavy weight.

Fact: If you start pushing past factory 7,500rpm limit with balance shafts, you're retarded

Fact: for every revolution the crankshaft makes, the balance shaft makes two. This means that at the pedestrian limiter of 7,500, your balance shaft is spinning 15,000 RPM. If you push out to 8500, it goes to 17,000. I'm spinning to 9,500 RPM, or 19,000 RPM on a balance shaft, on a belt about the size of a power steering belt. This teeny belt has the ability to catastrophically self destruct, taking out very expensive engine parts.

I didn't have clutch drag with an ACT2600 in 2005 with a stock motor, or with a built 9:1 motor with no balance shafts (Same clutch, same shitty transmission). I don't have clutch drag now with a twin disk, aluminum rod motor, and no balance shafts.

I'm not a Buschur fan, but LOL @ click

Also has some decent insight here click posts 6 & 7 seem relevant, but the whole thread, and jack's replies are worth reading.

I should add as a further case in point, the 4G61 does not have balance shafts from the factory. In fact, the proper parts to use for a BS delete come from Mitsubishi's parts catalog as OEM parts for the 4G61...

Realistically, this was ancient news when I got into DSM's in 2002...

vfaq - balance shafts






 

fuel

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Joined
Feb 23, 2009
Messages
2,165
Location
Toronto, ON, Canada
The only Sirius engine without balance shafts is the 4G61 1600cc DOHC. Engines of this small capacity don't require balance shafts - and that's why the 4G32 1600cc doesn't have them but the 1800cc 4G37 counterpart does. Every other Sirius ie 1800cc 4G62 and 4G67, 2000cc 4G63, 2400cc 4G64 and 4G69, 4D65 1800cc diesel and 4D68 2000cc diesel have balance shafts.
 

tektic

Well-known member
Joined
Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
Fuel; I thought the same thing when I read that.

Only the 1.6l didn't have shafts because it was such a small engine. So thats one engine. I cant think of 11 others.

Mitsubishi even licensed the idea to Saab Volvo and Porsche.

Jacks write up was definitely without explanation. Did anyone read the full explanation in the second link?
 
Last edited:

raptorWagon

Well-known member
Joined
May 17, 2007
Messages
2,827
Location
Oak Harbor, WA
But as Fuel knows as well other engines that first had the balance shafts, the 4g52 2.0l and 4g54s 2.6l did have have non balance shaft engines early on in life.

Personally, I remove them from every engine I own, I see no reason for them to be there as it is unnoticeable that they were even ever there with them removed in both my vr4 and 4g64 swapped Starion.
 
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