Lightweight pulley wow

[Sportsguy83]

Originally Posted by 86drift

I'd like an answer to this before I install a LW pulley. When I have an engine built it is balanced together.

One of the things I first noticed driving this car was the slow reactions of the engine due to flywheel (and pulley) weight. I find my gear changes are faster with lightened flywheels.

Yep, that's the way I've done it too. But looking at the responses here and on other pages, i think it is not balanced together, i think that the balance holes were made only to balance the pulley by itself. Hopefully tomorrow someone from Perrin can chime in. I tagged them so they should get a notification.

[noAE86]

rotating assembly is always balanced together,

crank pulley, crank pulley bolt & washer, crank pulley key, crank shaft, rods, pistons, piston rings, wrist pins, wrist pin clips, flywheel, flywheel bolts, clutch cover, clutch cover bolts,

its not the good old days of 2t 3t toyota engines that you can slap together and turn key,
in the past with my high strung engines, we would mark every item to know exactly where it assembled back together down to the clips, + or - grams was the tolerance, and this made for a fantastically smooth revving engine,

given this day and age every factory has high tech assembly plants, there might be 5-10 grams differences between parts but if the numbers are any higher, the result is a fuel injected vibrator,

[serialk11r]

If the stock crank pulley and the new crank pulley are both "consistent" in mass distribution, then you could attempt to drill out a similar amount of material from the same location to get close to the stock balance right?

[Nezz]

Originally Posted by noAE86

rotating assembly is always balanced together,

crank pulley, crank pulley bolt & washer, crank pulley key, crank shaft, rods, pistons, piston rings, wrist pins, wrist pin clips, flywheel, flywheel bolts, clutch cover, clutch cover bolts,

its not the good old days of 2t 3t toyota engines that you can slap together and turn key,
in the past with my high strung engines, we would mark every item to know exactly where it assembled back together down to the clips, + or - grams was the tolerance, and this made for a fantastically smooth revving engine,

given this day and age every factory has high tech assembly plants, there might be 5-10 grams differences between parts but if the numbers are any higher, the result is a fuel injected vibrator,

Bahaha, and you mention the engine I've had my mitts in the most, before I got the money to pay folks. 13T fo lyfe!

Most powerful pushrod I4 Toyota ever made.

[Sportsguy83]

Originally Posted by serialk11r

If the stock crank pulley and the new crank pulley are both "consistent" in mass distribution, then you could attempt to drill out a similar amount of material from the same location to get close to the stock balance right?

It's a little bit more complicated than that... You will never really "balance it" by approach. The exact hole location is determined by a computer with much higher precision than what you are suggesting. What I mean by this is, how are you going to measure that "consistent" mass distribution, and how much is close enough?

Also, we still have not heard from Perrin, they might come in and say their Pulley is balanced.

[serialk11r]

Originally Posted by sportsguy83

It's a little bit more complicated than that... You will never really "balance it" by approach. The exact hole location is determined by a computer with much higher precision than what you are suggesting. What I mean by this is, how are you going to measure that "consistent" mass distribution, and how much is close enough?

Also, we still have not heard from Perrin, they might come in and say their Pulley is balanced.

What I meant was, if an undrilled pulley has, within acceptable tolerance, a center of mass right at the center (which it would if it had consistent density), then you could replicate the "adjustment" made by the drilled holes approximately by taking out material in the same spot. Since the pulley is keyed? you'd know exactly where to take material off. Might need to account for density differences, but a little balancing is better than no balancing.

[Sportsguy83]

Originally Posted by serialk11r

What I meant was, if an undrilled pulley has, within acceptable tolerance, a center of mass right at the center (which it would if it had consistent density), then you could replicate the "adjustment" made by the drilled holes approximately by taking out material in the same spot. Since the pulley is keyed? you'd know exactly where to take material off. Might need to account for density differences, but a little balancing is better than no balancing.

I guess that if you the mas distribution of the original pulley is exactly or extremely similar to the LW pulley than certainly yes, you would be able to accomplish what you want.

[eriktherod]

I'm fairly sure the 4U-GSE/FA20 is balanced already. This same issue comes up all the time and gets annoying. From what I've seen nearly all of the time, V-shape engines have more demand for harmonic dampeners whereas straight and flat engines typically do not.

Honestly, do you think PERRIN, with all their design time and expertise would just "overlook" this very fundamental issue on a performance part? Feel free to await their response but I'm sure it'll be along these same lines.

I'll be ordering this and doing the mod in the coming month.

[atledreier]

So what exactly does this do, since the work is apparently worth it for every service.

[subaruferrucci]

it reduces rotational mass. they say takeing 1 pound of rotational mass is like 2 pounds of not rotational. If anyone has ever put some light weight wheels on the car or some supper heavy wheels i bet felt a difference in the engine response.

One of the many perks of a boxer engine is that is naturally more balanced. when you have one piston flying out on the opposite side you have one going out. On other motor types inline or V it is a very harsh.

Aircraft recip engines dont have any kind of dampener on them and they def run for a very long time

[Captain Snooze]

Originally Posted by subaruferrucci

One of the many perks of a boxer engine is that is naturally more balanced. when you have one piston flying out on the opposite side you have one going out. On other motor types inline or V it is a very harsh.

Incorrect. It depends on the number of cylinders and configuration. Inline 4; unbalanced. Inline 6;balanced. As for vees it depends on on number of cylinders and vee angle.

[White64Goat]

The one question that has still to be answered is: Is the stock pulley/balancer balanced on it's own or is it balanced as a complete rotating assembly. This isn't a 'I think it is' or 'probably' or 'the older engines did this or that' question. It's a black and white question. The holes drilled in the pulley/balancer are to balance the pulley or drilled to balance the whole assembly.

Then once you have the answer to that question, you have to ask that if you install an aftermarket pulley (any brand) that is a balanced pulley (on it's own) will it change the balance of the rotating assembly?

Does this make sense, or is my reasoning off base?

[boredom.is.me]

I think it is a lot simpiller than everyone is making it seem. If the stock pulley is balanced on its own, then the crank must be balanced on its own.

Mount the stock on its own shaft and bearing assembly and give it a good spin. If it is uneventful (meaning no obvious oscillation), then it is balanced independent of the crank. And if that is the case, then so is the crank.


I wish I had the car...

[noAE86]

Originally Posted by White64Goat

The one question that has still to be answered is: Is the stock pulley/balancer balanced on it's own or is it balanced as a complete rotating assembly. This isn't a 'I think it is' or 'probably' or 'the older engines did this or that' question. It's a black and white question. The holes drilled in the pulley/balancer are to balance the pulley or drilled to balance the whole assembly.

Then once you have the answer to that question, you have to ask that if you install an aftermarket pulley (any brand) that is a balanced pulley (on it's own) will it change the balance of the rotating assembly?

Does this make sense, or is my reasoning off base?

question is valid,
its a balanced complete assembly from factory, all auto makers have been doing this for ages,

when they produce engine parts, they get a "first balance" after casting/machining it is a clean up of swof from casting/machining and making sure stuff is in tolerance then its lotted into its own weight/grade (some auto makers tag the parts with bar codes at this point to keep track)

assembly means taking 4 rods of the same grade/weight match with pistons of the same grade + crank + other rotating mass, final balance in a machine will see all the little drill holes all over the crank pulley/crank shaft counter weights and flywheel,

so yes it is a matched set of parts from factory,
this also rings true why toyota has 3 factory grades of engine bearings/ not sure if subaru does too.

i know when lotus gets there toyota engines they do even more balancing,