balance shaft

[the_jester]

i have been reading in the vfaq pages and those other links. and i have found info on removing the balance shaft. and i have some experience working on engines but mostly just old chevy smallblocks. which have none of these parts. anyways what is the benefit from doing this. and another question has nothing to do with dsm's i have a porsche 944 turbo and i am restoring it. the belt is off the balance shafts, i dont know if they have to be in time with anything. anyway any info on balance shafts would be welcome

 

[BUCK]

Every expert I know on these boards says it's the greatest Mod you can do - I just did mine myself this year & I fully agree with them - You pick up a little vibe in the Steering wheel at idle - looking at the motor in the engine bay you'll swear it idles smoother - The motor sings after you get rid of those heavy POS's - It's unbelievable that any engineer anywhere dreamed those things up for as little good as they do vice all the HARM THEY CAN DO! During the mid-life crisis maintenance period on the front of these motors of our vintage you are almost 90% to getting rid of them anyway - anyone who doesn't is absolutely NUTS.

And I wouldn't TOUCH that Porsche until you knew the answer in advance.

 

[the_jester]

well then i will re-read that lijnk about getting rid of the balance shaft and think about doing it

 

[BUCK]

If you 90 is anything like my 91 it's time for a water pump - Harmonic balancer - front case oil seals, etc, etc - the balance shaft mod is a piece of cake while you are in there doing stuff you're crazy not to do while you are in there anyway... Good Luck!

 

[Defiant]

The balance shafts are "Silent Shafts". Their purpose is to cancel out the secondary vibrations inherent in 4-cylinder inline engines. The 944's shafts are in there under license from Mitsubishi. And yes, they have to be timed.

 

[the_jester]

thanx Defiant, is that something that i can do on the 944 or is it something only a porsche shop can do. sorry to ask this on a dsm forum

 

[Morphius]

Originally posted by BUCK
It's unbelievable that any engineer anywhere dreamed those things up for as little good as they do vice all the HARM THEY CAN DO!

Not here to rip, but to inform and stick up for us "engineers"

Given you don't understand the dynamics of the harmonics associated with the engine, then how can you say they do nothing? Remove them and run the car for 150K and then report what has now deteriorated because of the added vibration. What may feel acceptable to you, may not to the average customer. Worse yet, what might feel acceptable to you or anyone on this board, could be detrimetal to the engine, mounts or other engine mounted electronics on the long haul. Vibration KILLS electronics.

The b-shafts are there for a reason. It's added cost to add them. Believe me, we take out ANY cost we can out of ANY part. And try to do it without sacrificing Quality for the customer, you. I'm sure the need for them far outweighed the "potential" for the belt to go bad.

BTW Buck, it was my balance shaft belt that I let the magic smoke out of this weekend. Although, I should remove the balance shafts, I think I'll keep them in. No time this winter to do it. Thanks for the input and advice.

-DaimlerChrysler Engineer

 

[BUCK]

Engineers are good things - they CAN get carried away at times - the Atom Bomb, etc...

Several good points there Morph - Mitsu does make "similar' motors with no balance shafts I might add - & honestly you will be AMAZED at how little difference they make from a comfort standpoint at idle & NO vibration difference running - it certainly seems to run better & most people agree with that opinion - still smoother than the vast majority of 4's IMO & a GOOD Enginner could have damped that steering Wheel vibe at idle...

BTW - an exploded view shows the balance shafts in opposite positions when any pair of cylinders is at TDC - 1 weight up - 1 down. - What do you think would happen if someone in your position - who has to run only one balance shaft for a while - "split the difference" so to speak & mistimed the remaining rear shaft to have the weight rear - or forward - when any pair is TDC - Could that not be smoother than what you have now? I certainly can think of no one more qualified to answer this... Wanna try it & let us know?

 

[Defiant]

Originally posted by the_jester
thanx Defiant, is that something that i can do on the 944 or is it something only a porsche shop can do. sorry to ask this on a dsm forum

So far as I've understood, it's illegal to touch anything under the hood of a Porsche if you're not in a Porsche shop wearing Porsche overalls over freshly-laundered Porsche underwear -and collectiong Porsche-prices.

Other than that, it's just a matter of getting the instructions. Surely the web is even more widely-spattered with Porsche info than it is with DSM stuff.

Apologies for my thinly-veiled, seething rage at all things Porsche. I remember days that you could get as many 356's as you could stash for $600 on the streets of Berkeley. And it was too much for them, then.

 

[Morphius]

Originally posted by BUCK
- honestly you will be AMAZED at how little difference they make from a comfort standpoint at idle & NO vibration difference running - it certainly seems to run better & most people agree with that opinion - still smoother than the vast majority of 4's IMO

Until you attach an accelerometer to the engine and measure it, I don't think that statement is true. There will be a difference. How much? Don't know, but it's measureable. The frequencies are likely so high that they are undetectable by a human. Can you feel the difference between 8K hertz and 8.5K Hertz? What about a 2nd vs 4th order vibration at 6K hertz? Likely, no one can. Yes, I do agree "subjectivly" that it may appear that it's no different. In reality, it is. Why would they add them just for the added cost? (block material, machining block, shaft assemblies, assembly, bearings, belt,etc)

Originally posted by BUCK
- a GOOD Enginner could have damped that steering Wheel vibe at idle...

ANY engineer could have, but again, it comes down to cost. Plants don't like complexity. If you can commonize to one part...... all the better. For example: The Ram and the Dakota will have a common lower shift boot for 2005. Saves complexity at the Warren Truck Assembly plant, here in Michigan. They only have to deal with one boot. And in the end, given the added volume, the piece price drops dramatically. This all equates to a cheaper vehicle to build, sell, repair. Given the 2.0L needs a damper, where do you add the unique part? So in the case of the steering wheel damper, I'm sure they wanted one steering column assembly. That column is in EVERY car. There is no unique "2.0L column". Given the 2.0L was a unique assembly itself and had to be, they designed the "damper" into the engine.

Originally posted by BUCK
What do you think would happen if someone in your position - who has to run only one balance shaft for a while - "split the difference" so to speak & mistimed the remaining rear shaft to have the weight rear - or forward - when any pair is TDC - Could that not be smoother than what you have now? I certainly can think of no one more qualified to answer this... Wanna try it & let us know?

I follow your logic. May work and I could try it. I'll post back here later this week after I get it back together if I did it. And how it drives.

 

[AWD92TalonTSi]

as an engineer in training here's a few observations.
there's plenty of 2.0L cyl out there without balance shafts, granted not all engines are the same but close enough.

i noticed in my roommates 2.0 cougar that it had minimal vibration at idle and noticable in the 4-6k range.

why did mitsu put in these shafts and ford did not?
i came up with one thing
- the average rpm range of the engine, the cougar not being a sportscar will have a much lower average rpm than the turbo mitsu engine.

if this was a reilabilty issue i think ford(and many other companies) would be using balance shafts.

some of the things on the engine may have been designed around the balance shaft equipped engine, unforunatly there has been no data colleced as to part failures that could be based on the excess vibration.

needles to say mine are coming out on my rebuild.

just my .02

Bryan

 

[lowavenger96]

Toss them in the trash they do noting in a car that is going to be modded. As in bigger cams and bigger turbos will add to engine vibration already.