*Pulley and flywheel weights/ gains are NOT equil.*

Quick physics lesson:

Inertia: the unwillingness to move

There are two main factors that make up circluar Inertia; Mass and Radius of the mass. The equation is I=m(r)^2. It's a bit more complicated, but it will give you an idea.

OEM Pulley:
Radius: 3in
Weight: 4lbs
Inertia:36 inlbs

LW Pulley:
Radius:3in (not an underdrive pulley)
Weight: 1.5
Inertia:13.5 inlbs

OEM Flywheel:
Radius: 6in
Weight: 15lbs
Inertia: 540 inlbs

LW Flywheel:
Radius: 6in
Weight: 7lbs
Inertia:252 inlbs

Pulley savings: 22.5 inlbs = can "free up" 1.8 ftlbs

Flywheel savings: 288 inlbs = can "free up" 24 ftlbs

This is why you have bigger "gains" with the fly wheel than the pulley. You can "free-up" up to 24 ftlb with the flywheel. Like I said; its way more complicated, the real numbers require intergration from calc. So the real "gain" numbers are lower, it's just to give you an idea. Pulley and flywheel weights is NOT equil.

The real idea of fly wheel and pulley is to get into the power band quicker (aka faster reving engine). Not "free up" hp/tq.

Here is the pulley I went with:
https://www.fitfreak.net/forums/2nd-...ht-pulley.html

Good post De36 I love it when somebody provides FACTS to make their point. Tried to give you a points bump but got the must pass it around message.

Physics nerds itt... ;)

Yeah after I typed it I realized what I missed...

I'm doing some research on aluminum vs chromoly for flywheel materials to see if there is any meaningful difference...

I'll be standing by for what you find out.. I have been leaning toward Chromoly but the larger amount of mass with aluminum would absorb more vibration and cancel out resonance.

Material of the flywheel does not really matter. Usually the clutch a=contact area is treated, either with a certain material, or machined in such a manner that it allows a long life/use out of it.

I personally would go for the cheapest flywheel that has at least 3-5 pounds of savings, then take to a machine shop and ask them to balance it for up to 10,000 rpm. The higher the rpm it is balanced at, the BETTER the balance. Its a matter of resolution and precision. If they offer a higehr rpm to be balanced at, that is better!

WHen I had my turbo crx, I took a used fidanza flywheel, had a shop remove another 1.3 pounds, and they offered a balance of up to 14,000 rpm. Never had a smoother running motor in my life, considering honda internally balances ALL their motors!!

What I found was basically this:

Aluminum is desirable because it's lighter... And some like that the friction surface is replaceable vs resurfaced...
Chromoly is generally heavier, and one piece, and stronger... And it does have some acoustical benefits albeit very slight...

The mfactory example is chromoly and cheaper than the aluminum fidanza, heavier by 2 pounds but still much less than stock...

I think I'll be going with the chromoly example... Slightly heavier may be beneficial to driveability, and I like the one piece aspect... You can easily get it resurfaced when the time comes...

.02

How much might a machine shop charge to balance one? Would they remove material or add?

Balancing technique varies depending on flywheel design. On the crx, they countersunk 3 small spots near each other on the engine side of the fylwheel.

I believe I was charged $130 to remove some weight and get it balanced. It was a matter of a morning drop off and an afternoon pickup. I do not know how expensive it is to simply balance.

For me, that charge came later on after I had destroyed yet another transmission. The old D series transmissions are not very durable past 300k miles when you had a super grippy 4 puck clutch!!

THMotorsports.net - Hottest Import Car Magazine News & Reviews & Performance Parts Here is a link that might be of benefit to someone. I've done some business with these guys in the past and found them to be knowledgeable and helpful..