Is Balance shaft elimination a bad idea on a daily Driver?

[Norcalgsx707]

So I got my car on some racks and I have the thing apart, the timing belt is off the oil Assembly and pump are out, oil pan plus the transfer case anyhting I should inspect and is it worth doing a balance elimination kit on a daily driver ?? I have all stage one mods minus a built head and cams..

 

[Cdc1221]

I'm sure that if mitsu thought it would be harmful, they wouldn't have made a stub shaft to eliminate their original screwup: those tiny bs belts breaking. A few Sirius engines didn't use them stock. Plus, that's what harmonic dampers are for.

Removing that extra 6 pounds of rotational weight will help improve power, response, and acceleration, though I doubt you will feel it. But every little bit helps

 

[WES_393]

Going to throw a question or two here - one on topic and the other a side topic: Granted, Mitsu came out with this BS to smooth things out during operation. Now removal is the norm to save our motors in case something happens. With removal, vibration can be the results and with this vibration, isn't it going to be extra wear and tear on these motors - reason why the BS system was introduced in the first place?

The rotating assembly is already balanced on it's own. The balance shafts are just meant to eliminate the vibration created by an inherently imbalanced engine design, like the I4. Even a professionally balanced 4g63 bottom end will shake the dash loose.

Side question .. on the DODGE 420A motor: Still a 4cyl motor, but this motor has no BS shafts. How did DODGE manage to get away from using BS shafts (along with a lot of manufacturers of 4 cyl motors in that fact) and come out with a motor that has no vibration issues?

Thx - DSM

It all depends on engine specs, weights, and materials. The 420a bottom end uses a shorter stroke and larger bore along with lighter duty internals, so the resulting vibration isn't as severe. However, they definitely jumped on the BS bandwagon for the SRT4 and it's 2.4 turbo engine.

 

[KuckFatrina]

My stock engine failed because of a balance shaft bearing. Here's a nice picture of it

You must be logged in to view this image or video.

 

[dalesmitsu]

Here's a good video discussing this topice. Plus, his Awd Eclipse is a street Daily with a/c and power steering.

https://www.youtube.com/watch?v=LR-1adDayQY

part 2 of the video

https://www.youtube.com/watch?v=DPhyazI1fYc

 

[LandSpeed-DSM]

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.

 

[boost97gst]

I kept my BS. I was a super noob though and next time the engine comes out, im deleting it. I dont spin past 7500 though, so i think im safe(as long as the BS belt doesnt break). And btw, even with the BS in youre probably going to to have solid mounts or inserts. My car shakes like hell , that BS does NOTHING for me.

 

[LandSpeed-DSM]

I was apprehensive about spinning even that high with BS in place. The motor in the car currently was rebuilt after a spun BS bearing took it out when the PO sold it to me.

My car shakes like hell , that BS does NOTHING for me.

But women love a ride in the "rumble seat"

Solid mounts, no b-shaft, big ass cam, twin open dumps and 4" exhaust through the hood = invest in scotchgard

 

[ishnish]

There are two balance shafts, front and rear. The front shaft is driven by the BS belt, while the rear is driven by the oil pump. If you remove just the belt, the front shaft stops spinning, but the rear keeps going.

You cannot just remove the rear shaft because oil flows through the center of it and you will lose oil pressure, so you must replace it with a stubby shaft (which has no hole through it's center) or cut the original and plug the hole.

Once the rear shaft is dealt with, without the BS belt, the front shaft has no way to turn, so there is no problem just leaving it in. The front balance shaft is fed oil through holes in the bearings so blocking these off will raise the oil pressure. As Wes mentioned, oil pressure is not affected if you leave the front balance shaft in, because oil is still able to flow to the front shaft. This is especially helpful when feeding your turbo from the oil filter housing because you may not need to run a restrictor to limit pressure. Also, when doing a BSE with the engine still in the car, the front shaft is a bi*** to take out, not to mention getting the bearings out and putting them back in, so it is a considerable amount of more work....

Anyway, to drive the answer home, yes you can leave the front shaft in

Thanks for the info man.

This is just my luck looks like it'll still be too hard to do.. *sigh*

 

[Mischif]

Only time you'll notice more vibrations due to the balance shaft elimination is at idle. I've actually played around with it, and anything below 1000rpms you will notice a slight vibration due to the absence of the shafts. Above 1000 and you can't tell a difference.

 

[Norcalgsx707]

So to ask the question again is it possible to do with the engine in the car, and since the engine will be flowing more oil can that create problems? wouldn't it be wise to compensate for that extra oil?

 

[DSM1G90]

The 420a bottom end uses a shorter stroke and larger bore

Guess it would help to research this more, for I found this answer in my Chilton's book on this question:

the 420A has a 85.5mm bore against the 83mm stroke making this motor "Oversquare" whereas our 4G63 motors are "Undersquare" with the 85mm bore and 88mm stroke..and needing the balance shafts to take out these long stroke vibrations.

Meaning the 420A can wind up quicker to reach torque.

 

[Mischif]

So to ask the question again is it possible to do with the engine in the car, and since the engine will be flowing more oil can that create problems? wouldn't it be wise to compensate for that extra oil?

On a 1g its easy, just remove the driver side and cross members and let the engine hang, will give you all the clearance you need. On a 2g its a bit harder to get the clearance needed, but possible. I helped a friend do it on his 2g. With just the driver mount removed there wasn't quiet enough clearance. He wound up standing on top of the engine pushing down on it while i pulled the shaft/front cover off.

 

[Norcalgsx707]

On a 1g its easy, just remove the driver side and cross members and let the engine hang, will give you all the clearance you need. On a 2g its a bit harder to get the clearance needed, but possible. I helped a friend do it on his 2g. With just the driver mount removed there wasn't quiet enough clearance. He wound up standing on top of the engine pushing down on it while i pulled the shaft/front cover off.

Lol sounds like something I would do if it works it works I guess ill give it a shot eliminating ti would be the best idea in my opionion if there are no known problems with engine getting over filled with oil my mechanic friend says that it wont hurt anything

 

[dot45]

Lol sounds like something I would do if it works it works I guess ill give it a shot eliminating ti would be the best idea in my opionion if there are no known problems with engine getting over filled with oil my mechanic friend says that it wont hurt anything

The issue is not the engine getting "over filled" by oil, but the oil pressure rising to dangerous pressures due to the blocking of the oil ports. That is why if you remove the front shaft, you must port your oil filter housing (OFH). If just removing the rear, I have read that sometimes you don't need to port.

 

[DSM1G90]

if there are no known problems with engine getting over filled with oil my mechanic friend says that it wont hurt anything

Just keep the oil level to the upper mark on the dipstick - plain and simple making no concerns on overfilling - which is something you plain don't want to do if you want problems down the road.

There is a reason for the two oil levels on the dipstick - low one meaning a quart is needed, and the upper one to quit adding oil.

-DSM

 

[9!'clipseDOHC]

Looks like this has been pretty well covered but I'll just throw my 2 cents in anyway. I lost my first 4G63t engine build due to a spun balance shaft bearing back in 2005. I will never run balance shafts on a DSM again. Also I didn't notice any additional vibrations from the BSE with poly engine mounts. I think anyone building a 4g63 for any reason (DD, street/strip, drag, Autox, rally, time trial, etc) should eliminate the balance shafts and never look back.

 

[GIIANT]

This weekend I came across this article from Jack @ Jackstransmissions;

Keep Your Balance Shafts!

Ever heard of this increasing torsional whip before? Or is it a "new" insight on the matter of BSE?

 

[boost97gst]

Damn..... Thats coming from a VERY reputable shop too. Something to think about for sure.

 

[gusu]

This weekend I came across this article from Jack @ Jackstransmissions;

Keep Your Balance Shafts!

Ever heard of this increasing torsional whip before? Or is it a "new" insight on the matter of BSE?

No it's not new. It's something you have a hell of a time fighting when trying to get a engine to rev past a certain point.

The engine design and balancing skills required to reduce it to levels where high RPMs are possible is a bi***. That is why the full race version of the 4AGE by TRD is capable of 240hp at 11k RPMs (Technically they make that at 8600 RPMs but the car continues to rev past that point). The motor is built from the ground up to reduce these vibrations.

If you want a more in depth article on the subject a few Formula 1 engine builders have covered the topic in insane detail. I couldn't imagine the skill required to make a engine capable of 18-24k RPMs. I know F1 now limits engine speed to 18k RPMs but that wasn't always the case.

Which reminds me, if you've never seen the old footage of Senna racing in the rain it's a must watch. The guy was unbelievable in the rain and would lap the entire pack just simply because he was a god at driving in the rain.

 

[LandSpeed-DSM]

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:
http://www.epi-eng.com/piston_engine_technology/crankshaft_torsional_absorbers.htm

No it's not new. It's something you have a hell of a time fighting when trying to get a engine to rev past a certain point.

The engine design and balancing skills required to reduce it to levels where high RPMs are possible is a bi***. That is why the full race version of the 4AGE by TRD is capable of 240hp at 11k RPMs (Technically they make that at 8600 RPMs but the car continues to rev past that point). The motor is built from the ground up to reduce these vibrations.

If you want a more in depth article on the subject a few Formula 1 engine builders have covered the topic in insane detail. I couldn't imagine the skill required to make a engine capable of 18-24k RPMs. I know F1 now limits engine speed to 18k RPMs but that wasn't always the case.

Which reminds me, if you've never seen the old footage of Senna racing in the rain it's a must watch. The guy was unbelievable in the rain and would lap the entire pack just simply because he was a god at driving in the rain.

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.

 

[95talongirl]

The rotating assembly is already balanced on it's own. The balance shafts are just meant to eliminate the vibration created by an inherently imbalanced engine design, like the I4. Even a professionally balanced 4g63 bottom end will shake the dash loose.



It all depends on engine specs, weights, and materials. The 420a bottom end uses a shorter stroke and larger bore along with lighter duty internals, so the resulting vibration isn't as severe. However, they definitely jumped on the BS bandwagon for the SRT4 and it's 2.4 turbo engine.

Yes, it has to do with NVH, so some use it, some don't. Chrysler used balance shafts before the 2.4L in the SRT. On their old 2.5L in the 80's cars, that engine had balance shafts; yet the 2.2L variant did not. So, like with the 2.4L, the longer stroke of the 2.5L warranted the "need" for more balance.

 

[95talongirl]

This weekend I came across this article from Jack @ Jackstransmissions;

Keep Your Balance Shafts!

Ever heard of this increasing torsional whip before? Or is it a "new" insight on the matter of BSE?

There's some valid points in there. However, if you are building a car to rev to those high ranges; then no matter what you are going to be fighting forces like that. On cars driven more conservatively, it's not that noticeable. What also helps is having the rotational assembly balanced. On my car, I had the crank,rods, and pistons, all balanced, eliminated the balance shafts... and it runs super smooth. Also it's got about 10,000 miles on it now. But I don't take it over 7500rpm. I did not notice a change in the oil pressure, either... just like his link pointed out. I did use the OEM kit to do it, as well.

 

[T is for TURBO]

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

I agree with this. The engine damper and full weight flywheel are far more effective at removing any damaging harmonics than a small belt is.

I think you'll see more oil pump failures caused by the use of a stubby shaft and over tensioned timing belt than damaged cranks and clutches.

I will take my chances with pretty tried and true BSE over my chances with set of shafts that spin at 21,000rpm and a belt that's just waiting to throw itself into the crank sprocket.

And if one is that concerned about harmonics, I would suggest a fluid type harmonic damper, as they are very effective at what they do.

 

[LandSpeed-DSM]

I want to first mention that I just installed a Fluidampr on the car, now that my OE unit has developed a chip that could eat at the belt..

But there are sanctioning bodies that will not allow viscous fluid dampers because in some cases after extended periods running at high-rpm the heat that results from their operation can cause them to become lopsided when they are no longer running, sit and cool off.

This of course beats the crap out of the bearings and sends vibration down the driveline leading to various forms of failures, but I have not heard nor read of this being prevalent with the ones we have available.

 

[T is for TURBO]

Interesting. So if that were the case, one would want to let the damper cool off with the engine idling?