My spyder is seeing probably roughly ~450 awhp with a stock 7 bolt with balance shafts. I plan to push this bottom end until it throws something out the side! I do drive this car everyday and most of the days I drive it, it gets a few WOT pulls.

I havent had it to the track yet since I just put a different clutch in it about 250 miles ago so it hasnt been launched. The first time Ill probably have some track times will be at the shootout.

If I was you I would delete the balance shafts, they are about as useless as tits on a hog Balance shafts do absolutely nothing towards balancing the engine rotating assembly, just an extra rotating weight to absorb the engine vibration. They are not really hurting anything but they will cost you few HP and if you remove them it might make your oil pump live longer.

You can spend 0 dollars and delete them using everything that you already have. The front balance shaft you can just leave in place and just take the balance shaft belt off, the shaft will block off all the oil passages. You can either leave the tensioner pulley in place or delete it and just replace the tensioner bolt with a shorter one.

For the rear shaft you will have to pull the oil pump off. It will be easier to remove the pump assembly if you unbolt the balance shaft from it. Once you take everything out you have two options. You can buy a tap and tap the hole inside the balance shaft further so you can use a longer bolt which will close the oil passage inside the shaft. After you tap the treads you will have to cut the shaft. There is a spot where the shaft has two indentations on opposite side of each other which is right outside of the oil pump casing, you can cut the shaft there. Make sure you clean up any sharp edges and that your replacement bolt is long enough to go past the oil feed hole on the side of the shaft.

Your other option is to cut the shaft in that same place but instead of tapping the hole you can have it welded shut. What I would do is find a bolt that will fit inside the oil port in the shaft. Cut the head off the bolt but leave like a 1/4" section of the bolt on the head. Stick the bolt on the back of the shaft and weld the head to the shaft. This will give you something to hold on to when you go to install that cut off piece from the shaft inside the oil pump.

When you have everything apart make sure that you use some scotchbrite and WD40 and clean up the surfaces on the shaft and inside the oil pump. I've done this to my oil pump that had 130k miles on it, it has about 160+k miles on it right now and I still get oil pressure well over a 100 psi above 5000 rpms.

You can buy a balance shaft elimination kit but I've seen those things fail. I've seen where the shaft replacement piece was made of soft metal and eventually wore out to a point where the oil pump locked up. I don't think there is a better piece to use inside the oil pump then what's in it right now.

Just few ideas for you if you decide to delete the balance shafts.

Just to add to what you said Alex, when you cut the rear bs, the hole in the balance shaft is around .260", perfect for a 5/16"x18 tap, and you can thread lock a set screw in place, which blocks oil flow to the end of the shaft, but leaves the oil hole on the bs journal open

Damn, awesome info guys. Thank you. Im keeping this thread in a fav folder so i can look it up when i pull the engine next. And Boost, Ill prob b pm'n you, thanks bud

Have a read through this
Keep Your Balance Shafts – Jacks Transmissions LLC

Balance shafts, aside from the friction and inertia they add, should have no bearing on your power goal.

Anticipated engine speed, their relationship to the oil pump, propensity of catastrophic failure and perceived NVH should comprise your rubric for removal.. or like many, myself included, just decide to dodge that bullet from the get go and use the OEM Delete hardware on any build. From mild to wild.

Leave em in I was pushing 487 awhp on my 1990 Talon and it had the balance shafts still in it.

What I don't get is: what does causes bearing failure when the BS shafts are continually getting oil ...

DSM1G90 said:

What I don't get is: what does causes bearing failure when the BS shafts are continually getting oil ...

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When rotating at double the crankshaft speed, any inconsistencies in oiling have a much more dramatic effect. The chance for failure is higher when spinning a couple of weighted dowels at 14k+ rpm rather then simply not doing it at all.

Its as simple as why keep it if you can just delete it. Balance shaft is as useless as can be.

My maintenance supervisor at work and I are building a tsi for the ohio mile, and is hell bent on removing his balance shafts. I read through the article on jacks transmission site and unless someone can explain it better who has more experience I will be using kevlar belts whenever I change my timing set and keeping mine intact. It makes a lot of sense the way he explains it and how it not only effects the rotating assembly, but is more direcly responsible for dampening harmonic vibrations into a flywheel/clutch/pressure plate/gears/driveshaft/rear diff... there are many examples and pics that illustrate the damage that happens as a result, as well as a good explanation of how it can be directly responsible for clutch drag at high rpm. I will most definitely be retaining the balance shafts in my gsx unless someone can point me in the direction of another article with the credibility and quality of content as jacks.

PieEyedPiper said:

When rotating at double the crankshaft speed, any inconsistencies in oiling have a much more dramatic effect. The chance for failure is higher when spinning a couple of weighted dowels at 14k+ rpm rather then simply not doing it at all.

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This says it all. I don't want anything in my engine spinning at 14,000+ rpms if it doesn't have to be there. There is going to be less chance of failure without them IMHO.

oh-b-1g said:

My maintenance supervisor at work and I are building a tsi for the ohio mile, and is hell bent on removing his balance shafts. I read through the article on jacks transmission site and unless someone can explain it better who has more experience I will be using kevlar belts whenever I change my timing set and keeping mine intact. It makes a lot of sense the way he explains it and how it not only effects the rotating assembly, but is more direcly responsible for dampening harmonic vibrations into a flywheel/clutch/pressure plate/gears/driveshaft/rear diff... there are many examples and pics that illustrate the damage that happens as a result, as well as a good explanation of how it can be directly responsible for clutch drag at high rpm. I will most definitely be retaining the balance shafts in my gsx unless someone can point me in the direction of another article with the credibility and quality of content as jacks.

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Jack's article is flawed. The balance shafts have nothing to do with torsional whip, and while much of it sounds intuitive.. its not sound science. Check out the links below.

LandSpeed-DSM said:

The belt absorbs vibration and energy, in a similar fashion as a damper does.

The shafts also float on a film of oil that accepts and cushions their non-axisymmetric mass distribution.

The balance shafts introduce more energy and more vibration into the engine, but in a manner that simply hides it from cabin occupants.

Jack is not the only person getting his hands dirty with these motors. He is also the only one I've found that has floated this theory. Ask someone like Marco what he thinks about BSE.

Having two lopsided, heavy rods spinning twice crankshaft speed is trouble waiting to happen. The Engineers at Mitsubishi even created an OEM deletion that did not require re-designing and re-tooling for a new block.

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LandSpeed-DSM said:

The flywheel, clutch, changes to stroke or compression are all things that effect whip and harmonics in the crank.. but not the balance shafts.

The balance shafts are only connected to the crank by what is basically a rubber band.

The problem is the difference in acceleration from piston to piston as they rise and fall in the even fire configuration. One will be on compression, the next on power, another on exhaust and the last one intake. All of these events contributes to the overall net torque and cause the crank to bend and vibrate.

The balance shafts do not directly affect this. They simply add a new vibration 180* of the second order harmonic being put off by the crank.. this is to "hide" the crank harmonics for cabin NVH considerations.

The balance shafts themselves have no effect on your shifting or providing any aid to the crank like increasing the weight of a node (flywheel for example)

If you are really keen to learn more, start with a paper like this:
Torsional Vibration in Automobile Engine Crankshafts

And here:
http://www.bhjdynamics.com/downloads/pdf/tech/BHJDynamics_Damper_Info.pdf
Or here:
Crankshaft Torsional Absorbers, by EPI Inc.



Which is precisely why in my ~10.5k rpm motor.. I don't want a pair of balance shafts spinning at nearly 21000rpm, weighing in at a couple pounds each.

That is a bomb waiting to go off.

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LandSpeed-DSM said:

The balance shafts, or silent shafts are not removing vibration.. instead they are adding more vibration at a phase 180* out that "cancels" the other.

It's something most inline four cylinders could use. It's a part of using an even fire crank in this arrangement. Pistons rising and falling with different accelerations that create a net force that cannot be overcome no matter how well "balanced" the assembly is.

So it is really only for comfort and NVH concerns. Not a necessity in the least.

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I read Jacks link a month or 2 ago. I have to question the logic. I do, however, plan on a fluidamper in the future. Very pricey but i have a lightweight flywheel so i could use the extra rotating mass on the end actually. That trumps a BS any day as far as crank whip goes.

The only time I would consider keeping the balance shafts would be in a 2.3 stroker. There could be some benefit in keeping them for that but everything else I don't see the point.

ShadyDoins said:

The only time I would consider keeping the balance shafts would be in a 2.3 stroker. There could be some benefit in keeping them for that but everything else I don't see the point.

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Please explain what benefit (besides perceived cabin NVH) is to be had from keeping BS in a stroker, and why specifically this applies to the stroker.

This will be the first of many questions for you chris. In the third link is this quote.

"It is well known that excitation of any component at or near one of its resonant frequencies will, in the absence of either substantial damping or opposing oscillation, cause the amplitude of the oscillation to increase without bound until the component fails. There are famous films showing bridge failures from exactly this phenomenon."

Correct me if I am wrong, but does this decribe a balance shaft? Or does the dampening factor of the crank pulley and clutch assembly add enough resistance to compensate? And if so, what effect would the light weight flywheel, light weight pullies and other lightweight mods (driveshaft) have on the dampening factor? You bring up a lot of good points about the rpms and I can see that if the oil cushion were to lapse even for a moment that catastrophic failure would result.

I am not trying to be argumentitive, but I've heard a lot about factory cranks holding a lot of power and I can't help but wonder if controling the frequency of these vibrations isn't the key, so I'm interested to say the least!! Also, the first page of the first pdf is the only thing that displays and I'd like to read the whole article if I could. Thanks for the links!

oh-b-1g said:

This will be the first of many questions for you chris. In the third link is this quote.

"It is well known that excitation of any component at or near one of its resonant frequencies will, in the absence of either substantial damping or opposing oscillation, cause the amplitude of the oscillation to increase without bound until the component fails. There are famous films showing bridge failures from exactly this phenomenon."

Correct me if I am wrong, but does this decribe a balance shaft? Or does the dampening factor of the crank pulley and clutch assembly add enough resistance to compensate? And if so, what effect would the light weight flywheel, light weight pullies and other lightweight mods (driveshaft) have on the dampening factor? You bring up a lot of good points about the rpms and I can see that if the oil cushion were to lapse even for a moment that catastrophic failure would result.

I am not trying to be argumentitive, but I've heard a lot about factory cranks holding a lot of power and I can't help but wonder if controling the frequency of these vibrations isn't the key, so I'm interested to say the least!! Also, the first page of the first pdf is the only thing that displays and I'd like to read the whole article if I could. Thanks for the links!

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That is what the crank damper and flywheel do for the crankshaft, yes. They act as nodes also. Removing mass from these, or moving the mass closer to the hub or axis of rotation can decrease the ability of these items to damp the harmonics. Decreasing mass having the greater significance.

The balance shafts do not damp or effect the crank its self. It cannot be compared to the way the flywheel or damper work because these are not only sharing the same axis of rotation but they are also physically attached to the crank.

They only serve to change the way cabin occupants perceive the second order harmonics produced by the even fire crank. Again.. they only introduce MORE vibration/energy in a manner that "hides" the crank harmonics. The crank harmonics are still there, with or without the shafts installed.

You'll have to excuse me. I'm on page 3 of the second pdf. Ill hold anymore questions till I finish. Its taki g some concentration to really comprehend, but VERY enlightening!!

The belt absorbs vibration and energy, in a similar fashion as a damper does.

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Prob why OHC motors loves belts due to their tendency to absorb the vibrations more than a chain - either roller or multilink - chain and ever match up with.

Heard horror stories on the 2.2L DOHC motor from GM: Strong bulletproof lower end, but the head design using a single row, roller chain with nylon tensioners was asking for trouble due to 'chain whip' causing links to snap and head getting destroyed.

Looks like if Mitsu created a motor that was undersquare, then this BS (excuse the pun) issue wouldn't be a factor since these units would have never been installed.

This is why the 420A has no BS shafts due to it being an undersquare motor.

-DSM