Alright gents, had a fun afternoon. Doing some highway pulls and after one during decel, I noticed a unusual vibration.

In past evos, I had a shop put a balance shaft 360 degrees out of phase. Felt similar to what I was feeling but the current situation wasnt as bad. But I still suspected something balance shaft related. Drove the car home as nothing seemed inherently wrong, under 3k rpm the car felt more or less the same. No smoke, oil pressure's good, car drove fine, no weird noises, just a slight vibration as the car climbed in RPM.

Got home, tore the lower timing cover off and found this:



Balance shaft belt sheered the teeth off.

Question is simple: I know for a fact that people sometimes run these cars without this rear balance shaft, is there anything stopping me from removing tension, cutting the belt and fishing the belt out and running it like this until I pull the motor this winter as planned?

Timing belt/balance shaft belt etc are all only ~20k miles old, and I'm in a situation where I'm going to buying a house soon and don't want to pull the motor for a refresh at the moment.

 

Is the shaft seized? If it is you should probably dig into that some more. I think you will run into problems only running one shaft. You can leave that shaft in place and remove the oil pump driven shaft, or remove both. I don't think its a good idea to just leave the oil pump driven shaft spinning though. I don't know what happens when you only have one shaft spinning, but probably all the shaking your feeling now is because of that.

P.S. You should research deleting the shafts if that's what you want to go about doing. There is some other stuff involved and different paths you can choose to take to accomplish it.

 

Just cut the belt, the shaft spins like butter, it's not seized.

Obviously there is going to be vibrations with running only 1 shaft, but it should theoretically be less vibration than running 0 shafts, the only reason you need two shafts is so as the weights roll horizontally, they cancel each other out. I think the shaking I'm feeling now, is because the rear shaft is actually out of phase (from the teeth sheering and belt thus slipping) which would be worse than if it weren't moving at all.

Thanks for the input.

 

I've eliminated the rear belt and had both shafts turned down and i feel no vibrations at all.

 

You can't have one balance shaft spinning and one not. Either need both, or neither of them.

 

The front shaft has to spin to run the oil pump. You can't just set the front shaft turned down. EDIT, missunderstood "turned down". yea, machined down would work fine.

If you just remove the rear belt, only the front shaft spins(from timing belt) while the rear would not spin (because small balance belt is removed). This is how mine has been for years.

 

That's great. Just because it kinda works doesn't mean it's right. He already notices the extra vibration that feels like an out of time shaft due to only one shaft spinning. That is a problem.

 

turned down is a machining term. Unless I'm mistaken he is saying he had the counter weight machined off the shafts. This is an extra precaution some people take instead of switching to the Mitsubishi stub shaft. It is believed that it is better for oil pump life to do this. There are aftermarket blank shafts available to accomplish the same thing.

With just one shaft spinning it becomes more of an unbalance shaft. They are made to work together.

 

Gotcha, yea that makes more sense.

 

You made it sound like its entirely not possibly. Didn't say anything about it being right or wrong.

OP can read below and decide for himself.
https://www.jackstransmissions.com/b...balance-shafts

 

This subject (including that article by Jack) have been beaten to death, raised from the dead and beaten again and again. That's why I advised OP to research, that post by jack is certainly not the final say on balance shafts.

 

1 balance shaft is entirely different from 2 or zero. But you clearly don't understand that. It's ok.

Both shafts create a vibration/harmonic frequency which is exactly the opposite of a vibration/harmonic frequency of one created by the engine. This cancels out both vibrations and you feel nothing in the passenger compartment.

With only one shaft spinning, it's creating the wrong vibration/harmonic frequency. So instead of canceling out the engine harmonic, it simply adds to it. This really isn't good...

With no balance shafts, you only have the vibration generated by the engine. Which isn't a big deal. There are plenty of inline 4 cylinder engines, they all create the same vibration due to what's called secondary imbalance. Balance shafts are added purely for passenger comfort in the engines that have them.

 

Since this thread is becoming a funnel for yet another balance shaft beat down, here are additional resources.

https://en.wikipedia.org/wiki/Balance_shaft

https://web.archive.org/web/20090224...ar/eb10330.htm

"Engines which use balance shafts are sometimes referred to as "externally balanced", and the balance shafts do not reduce the vibrations experienced by the crankshaft."

The device you want to actually help the crankshaft is a harmonic dampener. Personally I use a Fluidampr, but there are plenty of good options out there.

 

Exactly. Hence my comment that the purpose of the balance shafts is only for passenger comfort.

 

yep I agree. I argued the same thing in the last balance shaft discussion.