Fountainclimber

According to youngsters on the Nissan sites, they claim that there is absolutely no down side to removing the balance shafts from the 2.5L four cylinder.

Kits are available from a couple manufacturer's for about $90 and it looks easy to do.

Redline is a measly 6200 and it does get moderately buzzy at that speed. It is supposed to be internally balanced and the balance shafts run at twice engine speed.

Is anyone confident that removing them would or would not cause any problems?

Reed Jensen

Removing the balance shafts lessens the amount of mass that has to be accelerated and decelerate... just like a lightened flywheel... but four cylinder engines have an inherent balance problem called a "rocking couple". This is a secondary "imbalance" that causes a little end to end rocking... Four cylinder engines have had this for years... it is only recently that engineers have tried to eliminate it. If the primary balance of the engine is good, you can remove the balance shafts.... but I would be inclined to have the engine rebalanced taking into consideration the absence of the balance shafts. Theoretically the engine should already have a good primary balance. You can always take the shafts out and see if it vibrates excessively before tearing down the engine and doing a complete re-balance.

mcollinstn

Balance shafts in an inline 4 are for driver comfort, not engine integrity. As was said, the motor should have correct primary balance. The balancers are for secondary imbalance which is a comfort issue.

As a side note, though, we've taken them out of a lot of Sea Doo PWC's for people, but the benefit is minimal and the increase in buzz though the handlebars is noticeable.

Fountainclimber

Thanks for the input.

I found an other thread that explains that you have to cut the chain that drives the balance shafts with bolt cutters which makes it a one way operation unless you open up the whole engine to replace the chain.

I guess I'll leave it intact for the time being at least. It runs pretty good for an econ box with the few modifications I already made.

Almost time to start working on the boat anyway.

Thanks,

F