3 quick questions about balance shafts! :P

[DR1665]

NOTE: These start out newbie level, but the discussion I'm after is on the advanced side. Methinks this the right place.

1. Is it generally possible to "correctly" time an engine with a balance shaft out of phase?
2. If so, would said engine run right?
3. If so, how would the increased vibration affect longevity?

Reason I ask is:
1. When I timed the G54B in my Pajero last month, I know I got every single mark lined up 100% correct.
2. Now that I've tamed the Flying Spaghetti Monster that is the Mikuni feedback carburetor, the truck runs like a friggin' boss.
3. But above 3000rpm, it starts vibrating like a motherf*cker. I'm talking lumpy cams, solid motor mounts, 2000W sub, & MTs rubbing vibration.

Imagine a giant pager up on the roof. As you wind any gear out past 3000rpm, it starts vibrating the whole shittery.

I've also posted this on the Wire, but figured I'd ask over here too, as it's a theory I don't think we've ever discussed. Everyone knows BSEK doesn't increase actual vibration - just how much is felt by passengers. But if it were possible to correctly time an engine with an out-of-phase balance shaft, I wonder if all the mirror shaking and vibrations felt would pose a threat to the engine.

Sincerely,

Captain Halfarse. /ubbthreads/images/graemlins/grin.gif

 

[gvr4ever]

Not sure what engine your talking about, but on the 4G63, the rear balance shaft can gravity drop with the belt removed. Unless you watch it move and what direction and how far, it is easy to line the timing mark out of phase.

 

[prove_it]

Yes you can time a balance shaft out of time, yes it will vibrate the crap out of the car. As far as I know it shouldn't effect the rotating mass lifespan. Your not actually running the crank out of balance. Balance shafts work but creating vibrations that "cancel" out crank imbalances from combustion.

I might be wrong, but I'd say your ok, but if it were me I would fix it sooner than later.

 

[DynastyLCD]

i did the same thing on my 2.4 SOHC Mighty Max years ago. it was easy enough to do, so i fixed the problem right away.

 

[desant78]

I'd try to remedy that as soon as possible. The motor is now producing vibrations much larger than without the vibration shaft (asssuming a worse case scenario). Since it was not designed to vibrate so much, I'd be scared of an induced fatigue failure. The rotating mass and vibrations on the crank won't change, just now your adding stress to all your fasteners who are vibrating more, and stressing the motor mounts. These vibrations are also now felt throughout the drivetrain too. I don't have expierence with cars and vibrations, but do test for vibration a lot, and once your resonating, failure quickly follow (which from what you describe is happening). This is my 2 cents, good luck!

 

[ktmrider]

Quoting prove_it:
Yes you can time a balance shaft out of time, yes it will vibrate the crap out of the car. As far as I know it shouldn't effect the rotating mass lifespan. Your not actually running the crank out of balance. Balance shafts work but creating vibrations that "cancel" out crank imbalances from combustion.

I might be wrong, but I'd say your ok, but if it were me I would fix it sooner than later.

^^ Agreed.

Did it on #86 back in the day and she ran just like you described. Made the knock sensor go crazy too.

 

[CutlassJim]

Quoting DR1665:
Everyone knows BSEK doesn't increase actual vibration - just how much is felt by passengers.



This is incredibly false. Anyone who has driven a car with balance shafts and then without knows it increases vibration. It doesn't increase the FORCES that are happening. Having them in ADDS a force opposite to the existing force and eliminates vibration. Not having them let the doesn't eliminate the vibration therefore increasing vibration.

 

[turbowop]

That's exactly what Driggs was trying to say.

 

[DR1665]

Thanks guys. This is on the G54B.

Timing it was far, far easier than any 4G63/420A I've ever worked on. Line the plated chain links up with marks on the sprockets, slide the sprockets onto their (indexed) shafts, DONE! But as I was driving to work yesterday, I got to thinking, "If you leave the balance shafts in on the 4G63, you're supposed to slip a screwdriver into that little hole to keep the one from moving. I didn't do anything like that on the truck. Bet they were both hanging down when I started timing this thing." Thus my question.

And, just to confirm I know how these work, I know the purpose of the balance shafts is to ADD vibrations which counteract the natural frequency of the rotating assembly in order to reduce the amount of vibration and noise felt/heard by the occupants. So, since these things ADD vibration, running one of them out-of-phase is ADDING vibrations in frequencies above and beyond what it was meant to handle. That's the confirmation I'm looking for.

Problem is, to get a G54B to the point where you can access the timing chains like this:

You gotta pretty much strip the block like this:

Thanks guys.

 

[prove_it]

Yep, that is what balance shafts do. Well besides cause failed bearings and loss of power....... /ubbthreads/images/graemlins/smirk.gif

 

[curtis]

Well this is kind of on subject but maybe not really. I spent about 10 years of my adult life around aircraft. Apaches, 58's Hawks and hooks then later to civilian junk everything from Citation X to old school pipers, beach bonanzas and baby cessnas. Vibrations can screw sh*t up almost instantly on an aircraft. Anywho some 4 cylinders don't have such things to begin with then when you turn them up and start spinning them well past the factory redline vibrations start changing things, like weakening the metal on a microscopic level changing the grain structure even on case hardened parts.


Here's a prime example. My buddies b series Honda we built a few years back. Motor had about 4K miles on it total in about 2 years. He spins the crap out of it and never had the boost much past 15 psi.

60 to 150 if you want to watch.... click me Car started over heating last fall. Car acted just like it had air in the system. We changed thermostats sensors burped the damn thing 2 dozen times but would be fine then go to crap and be fine again. Drove us nuts for weeks. Then the car sat for a few weeks while we put on the widebody front end and made a few changes and he took it to buff the new paint at another friends house and after it was finally detailed took it on a run down the interstate to test the car before the import alliance car show in Nashville the next day. Hard pull in 3rd then 4th and lifted and turned down the ramp. Half way down the ramp oil light came on but no noise, he took a right went about 100 yards to a gas station and checked the oil. NO noise when he started so he started home Thinking it was just a sending unit ......then the gravel noise started and he pulled over.


Well bad sh*t happened. Towed it to a friends garage so he could tear it down over the winter and this is what the oil pump looked like






Case hardened gears plus metal fatigue equals a slight drop of oil pressure. /ubbthreads/images/graemlins/grin.gif I believe the inter ring cracked at the flat areas on the crank first then caused the driven gear to then have a catastrophic failure. One thing we did find was the calico coated bearings saved the crank and rods. Only damage to the engine was the oil pump. /ubbthreads/images/graemlins/dunno.gif Got lucky. Its at the machine shop now and getting new big boy rods put in and hot tanked decked etc but no damage besides the pump. Now before anyone says should have got a factory pump it was a factory one. From all the research we did the fix for this is a ATI balancer instead of the factory one. Thank God the 4G63 has a gear style pump over the Honda design or I'm sure we would be killing them as well.



So what I figured was the oil pump was loosing pressure and causing an increase in heat in the motor and the coolant system couldn't keep up because the head gasket looked fine and its a fancy sleeved block and has no cracks there either.



I personally would be tearing the truck down Saturday to get this lined back up and everything in phase. Sorry for the rambling but this shows what bad vibrations and rpm's can do.

 

[raptorWagon]

Quoting DR1665:

2. Now that I've tamed the Flying Spaghetti Monster that is the Mikuni feedback carburetor, the truck runs like a friggin' boss.




Yep, only took me 3 weeks and several different carbs. Should upgrade to Sidedrafts though /ubbthreads/images/graemlins/grin.gif.

 

[Gizmovr4]

Did you replace the balance shaft chain? If so did you match the chain to the one you removed? Did all the shiny timing mark links match up to the old chain?

Many aftermarket chains have the timing mark Links in the wrong location – They actually want you to use their crank sprocket which has the timing dot also in a different location to match their chain.

I realized this a few times while building starquest engines….