Balance shaft delete discussion.

[GenDBlade]

I thought there was already a thread on this a few years ago, but i failed to find. Anyways.

I've been looking around the net seeing why other car guys believe its worth it, the biggest ones i seem to see it that its A) Supposedly more power due to less rotating mass(which id like to see some actual proof of), B) Peace of mind, in case the balance belt snaps and gets tangled up in the main timing belt, and C) Higher oil pressure.

So what are your opinions on doing this procedure, and does anyone have any hard evidence of increased HP.

Aaaaaannnnnd GO!

[Domesticated]

Yes you'll technically free a few, yes you will have less moving parts, yes you'll gain oil pressure.

Why does literally a few hp matter, have you ever heard of the balance shaft system failing, why do you need more oil pressure?

Lastly, you will increase the wear on your bearings and oil pump.

[wagon-r]

Yes you'll technically free a few, yes you will have less moving parts, yes you'll gain oil pressure.

Why does literally a few hp matter, have you ever heard of the balance shaft system failing, why do you need more oil pressure?

Lastly, you will increase the wear on your bearings and oil pump.

Mostly right. Except that you will not increase the wear on the bearings and oil pump. The balance shaft impacts happen AFTER the pistons and bearings do their thing. The balance shaft merely counteracts some of the vibration after the vibration occurs, so that you don't feel it inside the vehicle. But at the level of the bearings and oil pump, the balance shaft has no effect.

[steelbluesleepR]

Mostly right. Except that you will not increase the wear on the bearings and oil pump. The balance shaft impacts happen AFTER the pistons and bearings do their thing. The balance shaft merely counteracts some of the vibration after the vibration occurs, so that you don't feel it inside the vehicle. But at the level of the bearings and oil pump, the balance shaft has no effect.

do you have any empirical evidence or engineering to back that statement up?

[Domesticated]

Mostly right. Except that you will not increase the wear on the bearings and oil pump. The balance shaft impacts happen AFTER the pistons and bearings do their thing. The balance shaft merely counteracts some of the vibration after the vibration occurs, so that you don't feel it inside the vehicle. But at the level of the bearings and oil pump, the balance shaft has no effect.

Talk to the large displacement 4 cylinder Porsche guys. They have actually documented a loss after removing them. The balance shafts have the largest effect on the largest displacements and a smaller affect on our engines, but the damage still occurs. It's Allah week documented in the Neon 2.4 community that the vibrations are very hard on the contact surface of oil pumps. Fundamentals physics man, it takes energy to make vibrations.

It's basically a bragging mod. A dyno could tell the difference, I doubt your as could. Also another engines feel and sound better, outside of harshness/comfort reasons, it just feels like a better machine.

[illinois_erik]

I wonder why the B20 didnt have any, I guess those 12 cubes really make a big difference in our engine and the H vs. a 2 liter or 1.8 with similar piston/rod specs as a dohc 2.2L..or maybe its the fact the accord was the premium end of honda line and they wanted to make the driver sensation as pleasant as possible in their flagship hence the awards for years.

[steelbluesleepR]

I wonder why the B20 didnt have any, I guess those 12 cubes really make a big difference in our engine and the H vs. a 2 liter or 1.8 with similar piston/rod specs as a dohc 2.2L..or maybe its the fact the accord was the premium end of honda line and they wanted to make the driver sensation as pleasant as possible in their flagship hence the awards for years.

different motors have different dynamics. the engineers obviously made that choice for some reason.

[sonikaccord]

I agree with domesticated. Why add high order harmonics to these moving parts.

A balance shaft dampens those harmonics, even the ones you can't feel. (Assumption made through my physics knowledge, I have not seen proof) Vibration is energy, so it has to go somewhere...

[johnl]

Mostly right. Except that you will not increase the wear on the bearings and oil pump. The balance shaft impacts happen AFTER the pistons and bearings do their thing. The balance shaft merely counteracts some of the vibration after the vibration occurs, so that you don't feel it inside the vehicle. But at the level of the bearings and oil pump, the balance shaft has no effect.

Agreed. The imbalances inherent in straight 4 engines exist whether or not the engine is fitted with balance shafts, and still create vibration. All the balance shafts do is create additional imbalances that cause vibrations that work in opposite phase to the inherent vibrations, the net effect is less vibration evident at the engine mounts. The vibration created by the balance shafts 'cancels out' the other inherent vibration, but each vibration is till reacted internally within the engine, and any stresses caused by them still exist. Not that any of these vibrations have any significantly adverse affect on the bearings (or oil pump), they don't.

Neither will deleting the balance shafts cause any problems with oil pressure. If the BSs are removed and the bearing oil feed orifices blocked off then the pressure in the rest of the lubrication system will probably rise slightly (good, especially if the pressure is not quite what it was when the engine was new), because pressure is no longer escaping through the BS bearings. If the shafts are left in position (but not rotating) then there will probably be zero affect on oil pressure, the oil is still being pumped into the BS bearings and still escaping through the clearances in the BS bearings more or less as it normally would. Either way, there is no affect on the oil pump.

I deleted the BS belt on my car, the only noticeable difference is a slight increase in high frequency vibration. When I first did this I thought I could detect a slight improvement in rpm rise when rev matching for downshifts, and a slightly faster rpm drop when shifting to a higher gear. These effects must exist, physics says they have to, but in reality I think they are so slight that my initial impression after belt deletion was primarily a placebo affect, i.e. I expect X so I feel X. The affect is certainly far less than replacing the flywheel with a much lighter one (which I've done, and the affect is certainly far more than placebo).

The only convincing argument for belt deletion IMO is that if the belt doesn't exist it can't do any harm if it were to break, but if the belt is changed when it's supposed to be it's very unlikely to break. I suspect that the cam belt is under more load than the BS belt, and more likely to break than the BS belt (no data for this, could be wrong).

[johnl]

Talk to the large displacement 4 cylinder Porsche guys. They have actually documented a loss after removing them. The balance shafts have the largest effect on the largest displacements and a smaller affect on our engines, but the damage still occurs. It's Allah week documented in the Neon 2.4 community that the vibrations are very hard on the contact surface of oil pumps. Fundamentals physics man, it takes energy to make vibrations.

Documented what loss? Deleting the balance shafts doesn't create internal vibration within the engine, it actually reduces it (slightly). That is, vibration of the rotating parts, the block will vibrate less, but there is more vibratory stress reacted within the block, not that it's significant.

Any vibration caused by the reciprocating components is still there and 'felt' by the crankshaft, whether or not the balance shafts are working. All the balance shafts do is set up an additional counter vibration that makes the engine 'feel' smoother than it actually is.

I'm having a hard time seeing how engine vibration can impact upon gear lobes in the pump. Large high frequency pressure fluctuations could do, but not general vibration.

[johnl]

I wonder why the B20 didnt have any, I guess those 12 cubes really make a big difference in our engine and the H vs. a 2 liter or 1.8 with similar piston/rod specs as a dohc 2.2L..or maybe its the fact the accord was the premium end of honda line and they wanted to make the driver sensation as pleasant as possible in their flagship hence the awards for years.

Rule of thumb; straight fours with a capacity of over 2 litres vibrate enough that the added expense of fitting balance shafts is worth it for the improvement in apparent smoothness, engines below two litres less so.

[sonikaccord]

Agreed. The imbalances inherent in straight 4 engines exist whether or not the engine is fitted with balance shafts, and still create vibration. All the balance shafts do is create additional imbalances that cause vibrations that work in opposite phase to the inherent vibrations, the net effect is less vibration evident at the engine mounts. The vibration created by the balance shafts 'cancels out' the other inherent vibration, but each vibration is till reacted internally within the engine, and any stresses caused by them still exist. Not that any of these vibrations have any significantly adverse affect on the bearings (or oil pump), they don't.

If the vibrations are canceled, how are they still reacting?

The main question here is does it matter? What is the short term effect? long term? I feel that in the real world it's all up to personal preference. If one wishes to remove the belt, shafts or both then so be it. It will make a difference in engine performance and feel. We don't know if it will affect reliability, or do we?

Someone is going to have to build 2 Honda engines, one w/ BS and one w/o. Track both of them for several hundred hours, break them down and perform x-ray microscopy to see potential failure modes.

[Tishock]

For a long time my plan was to remove them but I found this article and a few others very helpful. Its a long read but informative. I admit our CB7s don't usually have the same power outputs as what this shop deals with on a daily basis. But we should consider all possible detrimental harmonic forces before blindly following this trend.

http://www.jackstransmissions.com/pa...balance-shafts

[johnl]

I agree with domesticated. Why add high order harmonics to these moving parts.

Deleting the BS doesn't "add" anything. The "high order harmonics" exist whether or not BSs are fitted. All the BSs do is disguise them.

A balance shaft dampens those harmonics, even the ones you can't feel. (Assumption made through my physics knowledge, I have not seen proof) Vibration is energy, so it has to go somewhere...

BSs don't dampen the harmonics, they set up a secondary counter vibration that reacts against the inherent primary vibration. The forces involved are seen in the metal of the block, i.e. force A acts in direction B and through the block casting meets a force C which is acting in the opposite direction. If you were able to measure it there will be tiny (miniscule) cyclic elastic deformations in the block casting as these opposing forces strain the casting. If opposing force C is removed then force A is 'free' to vibrate the entire engine, rather than deform the block casting.

Yes, vibration is caused by energy, if the vibration is suppressed then that energy does have to go somewhere, and that somewhere is into the block where the infinitesimal deformation of the metal casting converts it into heat, that is picked up by the cooling system and passed to the radiator.

[sonikaccord]

Deleting the BS doesn't "add" anything. The "high order harmonics" exist whether or not BSs are fitted. All the BSs do is disguise them.



BSs don't dampen the harmonics, they set up a secondary counter vibration that reacts against the inherent primary vibration. The forces involved are seen in the metal of the block, i.e. force A acts in direction B and through the block casting meets a force C which is acting in the opposite direction. If you were able to measure it there will be tiny (miniscule) cyclic elastic deformations in the block casting as these opposing forces strain the casting. If opposing force C is removed then force A is 'free' to vibrate the entire engine, rather than deform the block casting.

Yes, vibration is caused by energy, if the vibration is suppressed then that energy does have to go somewhere, and that somewhere is into the block where the infinitesimal deformation of the metal casting converts it into heat, that is picked up by the cooling system and passed to the radiator.

Good job describing that as I was thinking purely theoretically (vector math) the job of the balance shaft. But now that you mention the imperfections of canceling forces, then it makes it that much clearer and easier to visualize.

Simply, the balance shaft "spreads" the vibration energy through the block material instead of having the block itself vibrate. Looking at it from this perspective, by the time the vibration reaches any critical components, the magnitude is close to negligible right?