Balance Shaft Removal??!?!?!

[dohcGST]

hey everyone i have heard about removing the balance shaft in our cars. Well i am tearing down the motor and i need to know if i need to think about doing this.....

i dont know what it is.. i dont know what it really does, i would just like to have some info about it.. also some pros and cons. Thanks

Please Email at [email protected]

 

[swing lo]

search and you shall find my young padawan

 

[BUCK]

You're CRAZY if you don't do it - I get a little vibe in the steering wheel at idle - & a little vibrator never hurt anybody...

 

[dohcGST]

i definatly will, but i alooking for how much it will cost?!?! and about how long it will take me to do this procedure. Thanks

 

[dohcGST]

also this is on a 2g, all i have read about is on a 1g.

 

[LousyDriver]

Bofore you re-design the engine, perhaps you should look into getting a mechanical engineering degree. After all, if the balance shaft were completeley unneccesary, wouldn't mitsubishi have saved millions of dollars leaving them out of the car?

A lot of people seem to think that deleting the balance shaft will give them more power. This simply is not the case. The balance shaft reduces engine vibration as it's primary function. It does take some small amount of power to spin it, but once it is spinning, it takes nothing to keep it spinning. It's equivalent to reducing the mass of your flywheel. It makes no difference in engine power, but does make a slight difference in how quickly the engine revs when in neutral. If you really do a lot of racing in neutral, then perhaps you should look into another sport.

Engine vibration, on the other hand, has all kinds of nasty consequences, like broken motor mounts, leaking belts and lines (because of excessive engine movement) and lets not forget driveline vibrations that can accelerate wear on axels, tranny's and differentials.

Look at it as a difference in energy. How much energy is required to get that little shaft in the engine spinning at a couple thousand rpm vs the energy required to get a 2800 lb car moving at 75 mph. The difference in energy is a factor of thousands, meaning that removing the balance shaft will increase your performance by something around a fraction of a percent.

I'm not saying you shouldn't do it. Granted, a lot of people have with no ill effect, I am just cautioning against the tendancy to modify the engine without understanding the real effect. How important is that fraction of a percent of performance to you, really? Do you finish a lot of races within a foot of the competitor? Do you wager thousands of dollars? If so, then you are far ahead of me and should have no problem completely ignoring my advise. But spending money on a mod that makes almost no measurable difference? Doesn't make much sense to me.

Some mods are clearly a great idea, and some systems were designed with cost in mind instead of performance. I just don't beleive that this is one of those.

 

[98RedGs]

swing lo
search and you shall find my young padawan

"Use the Search" is not an acceptable response by itself. Just because a question has been answered before, doesn't give you the right to flame the person for asking it again. If you are not willing to at least post the exact URL to the thread (or page) where the answer can be found, and explain how the info can be found quickly next time, then just move on and say nothing at all. Teach newbies how to find info, don't flame them for not finding it. Links to the VFAQ homepage are also not recommended. Link to the article.

Thank you.





http://shop.store.yahoo.com/machv/busracbalsha.html
A Kit to buy to remove the balance shafts
http://members.shaw.ca/costall/1000Q/answers-maintenance.htm
More balance shaft removal information.
http://www.ecanfix.com/~mdhamilton/balanceshaft.html
Thats a walkthrough of the balance shaft removal.

 

[DarthBulk]

Well said, LousyDriver. I agree with your sentiments. I would point out however, that there is one other advantage to balance shaft removal...it mainly applies to the drag race guys. Removing the balance shafts removes a few pounds of steel, lightening the car somewhat. Does it make a difference? If you're a drag racer it does It doesn't give you more power, but it reduces the mass that needs to be accelerated down the strip. This increases your power to weight ratio by reducing weight, not increasing power.

Just don't quote me numbers on how much...I can figure that out on my own. I am an Aerospace Engineer.

 

[LousyDriver]

DId I really say leaking belts and lines?

Of course, I meant hoses and lines. Or maybe just hoses.

Sorry if I sounded overly sarcastic. It's a common problem on these boards to re-read your post and find that it sounds arrogant and obnoxious, when that was not really the intent. I should learn to add a bunch of and icons.

 

[kpt4321]

Originally posted by LousyDriver
Bofore you re-design the engine, perhaps you should look into getting a mechanical engineering degree. After all, if the balance shaft were completeley unneccesary, wouldn't mitsubishi have saved millions of dollars leaving them out of the car?

Because then the car would vibrate more, and the general public wouldn't appreciate that.

The Mirage 1.6L motors, which have the same basic design, don't have balance shafts. If they're so important, can you tell me why these motors don't have them?

There are lots of things that come in these cars that a racer doesn't need.

A lot of people seem to think that deleting the balance shaft will give them more power. This simply is not the case. The balance shaft reduces engine vibration as it's primary function. It does take some small amount of power to spin it, but once it is spinning, it takes nothing to keep it spinning. It's equivalent to reducing the mass of your flywheel. It makes no difference in engine power, but does make a slight difference in how quickly the engine revs when in neutral. If you really do a lot of racing in neutral, then perhaps you should look into another sport.

Wrong wrong wrong.

You're right, it doesn't take much power to keep a shaft spinning. However, it DOES take power to accelerate the shaft! That's where you have output gains, by eliminating mass that the motor was to accelerate.

It sounds to me like you don't know what you're talking about with lightweight flywheels. If you do the math out, you'll find that taking half the weight off the flywheel is equivilant to picking up over 100 horsepower in first gear! The flywheel has a LOT of rotational inertia, and thus takes a lot of energy to accelerate.

Lightweight flywheels make a HUGE (not slight) difference in how the engine accelerates in neutral, and also how easy it is to shift, downshift, rev-match, heel-and-toe, and more.

Engine vibration, on the other hand, has all kinds of nasty consequences, like broken motor mounts, leaking belts and lines (because of excessive engine movement) and lets not forget driveline vibrations that can accelerate wear on axels, tranny's and differentials.

I don't run balance shafts, and nothing like that has happened to me. Have you even ridden in a 2.0L DSM with no balance shafts? An inline four cylinder motor is balanced so well to begin with that removing the shafts only makes a small difference. They are only there to cancel out the second order oscillations of the rod and piston anyway.

With the small amount of high frequency vibration that is created, you sure as hell are not going to have leaking belts and lines, or broken motor mounts.

Look at it as a difference in energy. How much energy is required to get that little shaft in the engine spinning at a couple thousand rpm vs the energy required to get a 2800 lb car moving at 75 mph. The difference in energy is a factor of thousands, meaning that removing the balance shaft will increase your performance by something around a fraction of a percent.

Yup. Nobody even said it would make you run 10's, your point?

A K&N filter doesn't add much power. Is it a good mod? Yes.

I'm not saying you shouldn't do it. Granted, a lot of people have with no ill effect, I am just cautioning against the tendancy to modify the engine without understanding the real effect. How important is that fraction of a percent of performance to you, really? Do you finish a lot of races within a foot of the competitor? Do you wager thousands of dollars? If so, then you are far ahead of me and should have no problem completely ignoring my advise. But spending money on a mod that makes almost no measurable difference? Doesn't make much sense to me.

And I'm cautioning you against making suggestions when you don't understand the real effect. All you're doing is suggesting things that you don't even understand.

Some mods are clearly a great idea, and some systems were designed with cost in mind instead of performance. I just don't beleive that this is one of those.

You're wrong. It's a good mod, if you can do it right.

 

[LousyDriver]

KPT4321,

first of all, let me say thank you for the reply, it's well thought out and thorough. From what I have read, I have no choice but to admit you are correct in that there are definate advantages to the balance shaft removal, and someone who is looking to make the fastest car, independent of all other concerns, will want to remove the balance shaft. But I feel (perhapse incorrectly?) that not everyone considers what they are giving up when they modify their car. Every change is a compromise, and a lot of people seem to think that small mods will make tremendous changes in performance, when in fact the change is moderate and perhaps not as important as they thought.

I know everyone here is looking for something different from their car. My post wasn't meant to sway anyone one way or another, just to offer my opinion on one aspect of the process, and perhaps bring up a subject that is rarely talked about on this forum. Sure, your car is fast, but is it fun?

 

[lowavenger96]

Take the shafts out this will give you a small power increse , but most importantly it will get rid of the probility of the frount balance shaft belt breaking and taking out the timming belt. the kits cost arround 50 bucks and it is worth it. I personaly did it to my car and do not regret it.





Oh ya by the way here is a link to one of the sponsers of this site that has the kit http://www.slowboyracing.com/Engine/balance shaft eliminator kit/Eliminator.html

 

[kpt4321]

Originally posted by LousyDriver
Sure, your car is fast, but is it fun?

How is that relevant to anything about balance shafts? Removing the balance shafts didn't really effect how fun the car is, or how fast the car is. The power increase is not noticable, and the vibration increase is not noticable.

In my opinion, yes, it is fun.

 

[dohcGST]

well after this, i cant to realize, mitsu put it there for a reason, so therefor i should just leave it there, because it isnt hurting anything, and yeah it could break and break your timing belt, but there is also a chance that you could spontaniously combust.... so it is just a matter of opinon

 

[BUCK]

You'll regret any decision that involves doing ALL the interference work needed & then leaving the balance shafts active - it's shear ignorance - You obviously need to absorb more info from DSM boards - Those that defend those shafts are living in "spider holes" - No matter what kind of rocket scientist they are... Space Shuttles blow up too... Those shafts are Over-Engineered pieces of crap.

 

[Morphius]

Originally posted by BUCK
Those that defend those shafts are living in "spider holes" - No matter what kind of rocket scientist they are... Space Shuttles blow up too... Those shafts are Over-Engineered pieces of crap.

Tsk, Tsk. Bad day Buck?

 

[Morphius]

Originally posted by LousyDriver
Bofore you re-design the engine, perhaps you should look into getting a mechanical engineering degree.

Check. There twice.

Originally posted by LousyDriver
After all, if the balance shaft were completeley unneccesary, wouldn't mitsubishi have saved millions of dollars leaving them out of the car?

True.

Originally posted by LousyDriver
Engine vibration, on the other hand, has all kinds of nasty consequences, like broken motor mounts, leaking belts and lines (because of excessive engine movement) and lets not forget driveline vibrations that can accelerate wear on axels, tranny's and differentials.

True. For longevity and reliablity of the OVERALL system, they are needed. I bet the power transistor and coil pack WOULDN'T last 150K on an engine without balance shafts.

For most of you here, you are enthusisasts. SO, removing them only takes out one potential failure while adding another. On the other hand, you aren't looking for a reliable 150K car. It's a tuner.


-DaimlerChrysler Engineer.

 

[Morphius]

Originally posted by kpt4321
They are only there to cancel out the second order oscillations of the rod and piston anyway.

Are you SURE about that?

What about:
ignition?
Injector pulses?
Cams?
Oil pump?

I've got plot of data we just pulled off a 2005 HO diesel. We installed an accelerometer on the clutch pedal. It's pretty interesting. There's more there than you'd think. I'll see if I can get it scanned tommarrow and post it.

-DaimlerChrysler Engineer

 

[LousyDriver]

I was tempted to let this thread drift off into the archives, but one critical point has been bugging me for two days now. People can call me stupid, people can tell me I don't know what I'm talking about, you can even call me a noob with nothing to offer, but when someone says I don't know my math, I feel the need to get academic on their behind.

I am about to say something that may piss a lot of people off, that may fly in the face of all that is sacred and worshipped on this site, but I feel it is my duty to say it. Someone has to.

The DSM will run the quarter mile faster with the balance shaft in place.

There. I said it. I am even willing to say it again. I'll shout it from the hills if I have to. I'll even clarify why I feel this is the case. It's all because of what KTP said about a lightweight flywheel being like "Adding 100 horsepower in first gear."

Actually, a 12 pound flywheel with an effective diameter of 40 cm spinning at 6000 rpm will store 5,500 watts of energy, or about 7 horsepower. If the stock flywheel weighs twice this, then it stores 14 hp.

That's at least 93 HP off from what was said above, but that's not the critical point.

Let me ask you, when you are sitting at the tree, and that last amber light is glowing, what are you doing? you'd better be revving the engine, if you plan to win this race. Reving the engine at around 5000 RPM right? what happens when you drop the clutch? the engine rpm falls, the car accelerates, and your off. WAIT A MINUTE! During the critical first second of the race, the RPM's are FALLING, not climbing.

What happened to all that energy that was stored in the flywheel, the crank, and the balance shaft? Well, it either spun the tires, wore the clutch, or ACCELERATED the car.

That's right, the energy stored in your flywheel is critical to launching the car. Any drag racer can tell you that the first sixty feet are critical to having a good run. A small difference at the beginning of the track translates into a huge difference at the end of the track. Having a heavy flywheel on a car that has poor traction will simply break the tires loose, but having a heavy flywheel on a car with excellent traction is an advantage.

Now, let recap. The flywheel (and also the balance shaft) is an energy storage device. The energy that is stored is generated by the engine BEFORE the green light flashes. This energy is then available to accelerate the car off of the line. The energy is robbed from the engine at the end of the track (but in between shifts, the energy stored in the flywheel is again available to accelerate the car) where it would have less of an impact on the ET.

As a final note, I repeat what I said above, the balance shaft is a rotating mass, equvalent to a heavier flywheel.

Now, the reduction in mass of the car as a whole is worth something, and it works against my argument above. As a conceptual tool, let's observe that it is possible to build a car that can travel the quarter mile with no engine, entirely on energy stored in the flywheel. (assuming the flywheel was spinning to begin with)

Now, I have asserted that the energy storage is enough to make up for the added mass. There is some RPM at which this is true, but at lower RPM this would be false. I have no way of calculating what RPM would be required to make this assertion true without dissasembling the car and weighing and measuring each piece. But it is certainly something to think about the next time the debate comes up.

And if anyone has detailed information on the moment of inertia of the driveline, we could actually determine if this is true, or if the RPM required to make up for the increase in mass is too high.

 

[Enigma_Man]

There has to be a point of optimal Flywheel weight though (assuming we're just talking about raw 1/4 mile times, and nothing else). If you go too heavy, you can launch like hell, because you have that inertia behind you, but you'll be slow to accelerate/move that mass around.

If you go too light, your launch will suffer, but your engine won't have that extra mass to rotate/accelerate.

But... now that I've been thinking about this, what I just said starts to make less and less sense:

I'm now curious to know how much extra power you get from actually having a heavier flywheel. It seems to me that the added acceleration due to a heavy flywheel is negligable when in comparison to the power that the engine itself makes (Maybe a couple of tens of extra ft-lbs for the first quarter second while the engine is decelerating/adding power to the driveline). Can anybody figure out these numbers? You said yourself that a stock flywheel at 6000 rpm stores ~10 horsepower that can be used when the clutch is dropped, and added to that. So.. you get +10 horsepower while the rpms are dropping, but then an average -10 for the whole run after that, because you're now having to accelerate that flywheel. However, if you have a light flywheel, you might only get +5 extra for the beginning of the run, but you only lose -5 the whole rest of the run (these numbers are imaginary, and just to prove my point).

I know that saying "what do the fast guys do" has its problems (the fast guys can _all_ be wrong on that rare occasion), but do you know anybody that sticks with the stock weight flywheel for serious drag racing? Or even goes with a heavier one?

Lousy, I think you're incorrect about saying that a car will run a faster 1/4 mile time with a heavier flywheel/balance shafts in place (essentially the same thing, more rotating mass). Yes, the launch is critical, and extra momentum from the engine's rotating mass can help a lot with that, but personally I don't think that overall, a heavier rotating assembly would make you faster.

Also, I thought the main benefit to removing the b-shafts was that you had one less thing to worry about breaking? An inline-four engine isn't perfectly balanced inherently, but it is not very unbalanced. I somehow doubt very much that extra added vibration is going to cause you more harm over the life of the car over the possibility of a broken b-shaft belt. Our engines shake and move quite a bit anyway, so the added percentage due to !b-shafts I don't think would have any real effect.

-Jesse

 

[LousyDriver]

It's true that I can't demonstrate conclusively that I am right (or that I am wrong, I'd be happy to know for sure either way), it all depends on the distribution of mass in the drivetrain, and at real engine speeds, the lighter flywheel might be better. The main point I was hoping to get across was that you aren't really getting something for nothing. There are drawbacks to each way of doing it. I just felt like I was getting slammed for insisting that this wasn't as great of a 'free mod' as most people think, and I feel my point about storing energy before the green was worth at least a little consideration. I presented my argument as if I firmly believe it, but I was careful to note that it depends on RPM/moment of inertia.

Avoiding the potential for damage to the timing belt is a good reason, and I have nothing against doing this mod, but I feel that keeping up with maintenance is also a good option.

 

[Enigma_Man]

Yeah, it was a very well constructed argument And I do agree, to some degree. I just don't think it makes as much of a difference as you think it will, but that's just my opinion on all of this. I personally believe that removing just about as much weight as you can from the drivetrain, including the engine (in a car) is a good thing. I don't actually have any real data to back this up, other than what I can imagine.

-Jesse, pro bench racer

 

[CYCLONE]

I think that you guys need to realize that the balance shafts
spin a lot faster than the crankshaft. I'm to lazy to find any
facts about it but looking at the size of the pulleys I would
say about twice the speed of the crank. So when the engine
is at redline the shafts are spinning at something like 14K rpm.
Therefore its pretty easy to spin some bearings on the balance
shafts. Especially for people that rally or autocross, because
the engine is at high revs for extended periods of time.

The only reason that I removed my balance shafts is because
the bearing on them walked out and made a big mess
in my engine on my last rally event. I would definetely recomend
removing them to anyone that goes racing.

 

[onedownfiveup_x]

Just to give people an idea. Balance shaft on the oil pump side froze on my g/f's Laser took out the timing belt and now we are looking for a rebuild. Time to make her faster though .

 

[kpt4321]

Originally posted by Morphius
Are you SURE about that?
What about:
ignition?
Injector pulses?
Cams?
Oil pump?

WTF? Are you trying to tell me that the balance shafts balance out the injector pulses? WHAT THE ####?

They balance out the "ignition?"

I don't even know what the #### you are trying to say.

Balance shafts balance out the second-order piston and rod vibrations, which occur in the front to rear plane of the vehicle. They spin at twice the engine speed, and only do balancing in the forward and reverse vectors.