eBay M20 Light Weight Pulley / Crank Dampner

[RobertK]

So I found this on eBay today..

http://cgi.ebay.com/ebaymotors/BMW-E30-325i-is-ix-ic-87-91-Light-Weight-Pulley-/200481366071?pt=Motors_Car_Truck_Parts_Accessories&hash=item2ead9ee037

Anyone have an idea of how well this will work with the stock CPS considering its made completely out of aluminum?

[whodwho]

The timing wheel is steel bolted on the pulley, there were some pic somewhere and you could see the fastners.

[nando]

no way I would run that thing.

[RobertK]

The timing wheel is steel bolted on the pulley, there were some pic somewhere and you could see the fastners.

Hmm... looks like a solid piece to me.

[Mike]

I've seen that before, but I never saw that it also replaces the timing belt pulley too...Guess the install is a little more involved than just removing the accessory belts and balancer assembly.

[Adrian_Visser]

Considering that the purpose of the harmonic balancer is to cancel out potentially catastrophic harmonic vibration waves set up along the length of the crankshaft I tend to think that taking away most of the weight wouldn't be a good thing. I mean think of how much extra noise and vibration it makes when you add a lightweight flywheel, this would be much worse. Lightweight pullies are one thing, and afaik they do fuck all, I have them on my s52.

[nando]

Hmm... looks like a solid piece to me.

it's not the construction that bothers me. we have really long crankshafts and the damper is very important to keep resonances and vibrations low. What would you really gain by this anyway?

[Jaxx_]

it's not the construction that bothers me. we have really long crankshafts and the damper is very important to keep resonances and vibrations low. What would you really gain by this anyway?

it's less of an issue than you'd imagine. seen people running a UR on a 5 cyl without any issue, even at 8k.


obviously it frees up horsepower by being, what it looks like, an under drive. it also is lighter to help revving. lowering torque too, though.

[nando]

a 5 cylinder also has a much shorter crank than an inline 6

what could it save you? 1whp? if you want weight savings use a lighter forged crank, rods and pistons. you can save about 5-7lbs with pistons and rods alone, far more than you will get by compromising an important peice of engine integrity.

it also doesn't lower torque. lol.

[Jaxx_]

a 5 cylinder also has a much shorter crank than an inline 6

what could it save you? 1whp? if you want weight savings use a lighter forged crank, rods and pistons. you can save about 5-7lbs with pistons and rods alone, far more than you will get by compromising an important peice of engine integrity.

it also doesn't lower torque. lol.

if we're talking about significance, it's like what, 15%? it's shorter, but I wouldn't say MUCH shorter.

we're talking about a few bucks vs modifying your entire rotating assembly.

oh, it doesn't lower torque? okay. Remind me again what happens to torque when you take weight off a flywheel? It doesn't matter what end you take the weight off, higher weight means higher moment of inertia, higher moment of inertia means more torque.

[NigelStu]

Where's the head-slap smiley face????


I don't know if it just me or my engineering background, but gee whiz, that torque comment seems backwards...




OP - it may help. but only if you are racing a very well prepped vehicle with nowhere else to lose weight and an otherwise maxed out engine build... Street car? Not gonna make a difference.

As far as it working - I would think that the trigger wheel would need to be something magnetic...

[Jaxx_]

Where's the head-slap smiley face????


I don't know if it just me or my engineering background, but gee whiz, that torque comment seems backwards...

theoretically, it's the same, but the concept could be seen the other way -- less weight means it's easier to slow the rotating assembly. WOT up a steep hill, more weight = more torque. make sense?

F=ma. It's the same final torque, but at a constant acceleration, you have more torque.

[NigelStu]

make sense?

No.


But then again, I'm using the assumption that the air/fuel mixture burning in the cylinder, creating pressure and thus moving the pistons down is what is creating the torque on the crankshaft.

[nando]

Where's the head-slap smiley face????


I don't know if it just me or my engineering background, but gee whiz, that torque comment seems backwards...




OP - it may help. but only if you are racing a very well prepped vehicle with nowhere else to lose weight and an otherwise maxed out engine build... Street car? Not gonna make a difference.

As far as it working - I would think that the trigger wheel would need to be something magnetic...

right. because extra mass in the drivetrain creates torque, not cylinder filling (VE) and combustion.

hey, want more torque? just add weight to the crank! who knew it was so easy? BMW has been doing it wrong all these years, making their roating assemblys lighter and lighter.

definitely need a facepalm smiley for this one..

[KenC]

No.


But then again, I'm using the assumption that the air/fuel mixture burning in the cylinder, creating pressure and thus moving the pistons down is what is creating the torque on the crankshaft.

You're assuming correctly.