Balance shaft delete (better MPG observed)

[stockMKIVTDI]

Originally Posted by IsaacCarlson

I just removed the balance shafts from our 2006 rav4 2.5L and I wish I had done it sooner. The difference is amazing. More power, better response, less throttle needed, and quieter.

It used to down shift on the hills around here and the rpm's would go way up. Now it just rolls right up the hills like they're not even there. Night and day difference.

I hope we don't get a speeding ticket, because it takes barely any throttle to maintain speed. It's going to take some getting used to for sure.

The engine is much quieter now. There was some "clattering" that we attributed to engine wear, but it's gone now. It had to be the shafts making noise. We can now whisper with the engine running, both inside and outside the car. All you hear is the injectors clicking and the exhaust.

The mileage should go up some too.

A lance shafts get removed in race cars too but be warned the extra vibration leads to extra bearing wear which will negate any gains in the long run. Better to just flush the motor by replacing the engine oil with some atf run it for 20 minutes at idle only. drain it replace filter and fill with regular oil. It cleans off any and all deposits that increase friction and decrease mileage. Especially in hydraulic lifter cars.

[IsaacCarlson]

Originally Posted by stockMKIVTDI

A lance shafts get removed in race cars too but be warned the extra vibration leads to extra bearing wear which will negate any gains in the long run. Better to just flush the motor by replacing the engine oil with some atf run it for 20 minutes at idle only. drain it replace filter and fill with regular oil. It cleans off any and all deposits that increase friction and decrease mileage. Especially in hydraulic lifter cars.

Bearing wear? The only bearings that were bad were on the balance shafts. That says something. How would a bit more vibration hurt my remaining bearings, especially with increased oil pressure? I'm calling BS on the "more wear from vibration" theory. Diesels vibrate like crazy. My inline truck motor vibrates enough to shake the mirrors at idle. I'm not worried about the tiny amount of vibration hurting the rav. I can barely feel it and nobody else can even tell it's there.

[stockMKIVTDI]

Originally Posted by IsaacCarlson

Bearing wear? The only bearings that were bad were on the balance shafts. That says something. How would a bit more vibration hurt my remaining bearings, especially with increased oil pressure? I'm calling BS on the "more wear from vibration" theory. Diesels vibrate like crazy. My inline truck motor vibrates enough to shake the mirrors at idle. I'm not worried about the tiny amount of vibration hurting the rav. I can barely feel it and nobody else can even tell it's there.

Wrong kind of vibration. I have a Cummins as well and any vibration you are getting there is due to bad mounts not internals. Those engines all run a harmonic dampener which does the same thing as a balance shaft. A balance shaft counters the harmonic vibration of the crank as 4 cylinder engines or aren’t able to equally apply force 360 degrees around the crank thus making them harmonically unbalanced by nature at higher rpms. The larger displacement of a cylinder the more effect that harmonic unbalance will have. Just about every 2.2l 4 cylinder or larger runs a balance shaft. Inline 6 cylinder and above typically don’t need one and only need a harmonic dampener. All that said since a balance shaft is just a counter rotating eccentric shaft or a weight and has little to no power drain so I have to call bs that you noticed any fuel economy difference. Now if you performed the removal in a controlled environment where nothing else on the engine was replaced tans even the same oil was reused then I would be more open minded. Also harmonic vibration engine damage is well documented thanks to years of research from racing.

[IsaacCarlson]

It takes a certain amount of power to rotate a shaft in bearings. It takes exponentially more to rotate an unbalanced shaft, with the amount of power going up as the shaft imbalance and/or rpm increases.

If I am wrong about the effects on mpg, please tell me where the extra mpg are coming from.

[JohnAh]

Off course it cost energy to drive a balance shaft, but I don't think it's much more than marginal in the end, if the bearings are ok. A balance shaft is in trouble from birth, simply because it's purpose is to cause imbalance to counter act the imbalance made by the pistons and rods. The piston-, rods-, and crankshaft assembly is on the other hand designed to be as smooth as possible, but doesn't make it all the way, hence the balance shaft in some engines. I don't find it strange that the balance shaft bearings may wear out quicker than the others.

The old German Ford V4 ("Cologne engine", used in Taunus and Saab 95/96 of the 1960's and 70's) is very prone to wear out in the balance shaft bearings. You can sometimes get an early warning if having an oil pressure gauge. When the bearings fail, it's not uncommon that the fiber plastic gear goes with them, and that will stop the water pump, the radiator fan and the alternator. That happened to me once, and after the failure the engine was running rough, but more silent, without the whining noise from the alternator. A 60 degree V4 without balance shaft is however way worse in balance than a straight-4.