LTW crank pulley question...

[MR 325]

I've got an S50 with M20 flywheel, E30 M3 clutch and Getrag 260 trans.

I've read conflicting info... Some say do NOT install a LTW crank pulley with a lighter flywheel already installed and other say it's just fine, no problem at all. Can anybody shed some more light on this?

I'm getting the car dyno tuned on the 21st and need to have everything ready.

[AL GReeNeRy]

ive been wondering as well. hey mr325 how much bigger is the m3 clutch disk vs the m20?

[lifeiskaos]

i wouldnt... these engines are very sensitive to harmonic frequencies and fucking with the harmonic balancer will make it worse. your parasitic loss isn't all THAT much. and if you're wanting under drive pulleys, you're sacrificing alternator current and water pump flow. just not worth it imo

[z31maniac]

I've got an S50 with M20 flywheel, E30 M3 clutch and Getrag 260 trans.

I've read conflicting info... Some say do NOT install a LTW crank pulley with a lighter flywheel already installed and other say it's just fine, no problem at all. Can anybody shed some more light on this?

I'm getting the car dyno tuned on the 21st and need to have everything ready.

From what I've read on underdrive pulleys' for 24v motors, the majority of "reputable" companies don't do a crank pulley because of the loss of the harmonic damper.

[hoveringuy]

I read somewhere about a race where every one of the cars with a lightweight crank pulley broke the crankshaft.

I wouldn't do it.

[SpecM]

the only thing I'd do it underdrive the p/s and alternator... MAYBE

[e30polak]

Quit trying to be a show off Matt! :hitler:

Seriously though it's not safe, I wouldn't risk it after all the time and money that's gone into your swap. If you want more power on the dyno just buy a 75 shot of NOS. ;)

[Beej '86 325es]

I watch the bimmerforums.com classifieds frequently, there used to be a TON of them for sale on there used. My thought is there has to be a reason for that. I wouldn't do it.

GL w/ the dyno! Post some graphs for us...

[matt]

There is a causal relationship between the replacement of the TV damper on the front of the crank with something that is not a TV damper and massive destruction.

Resonance is a bitch, sometimes.

[erik325i]

The crank pulley is not the issue. The harmonic balancer is. On the US motor where the pulley is attached to the harmonic balancer, I would never swap pulleys.
If the pulley is not attached to the balancer, as on the Euro motor, I would (and have) swap it out.

Erik

[mazur]

I used to have one. My engine would make a ringing sound under WOT aroung the 3k-4k rpm range, which was funny because an "engineer" over at bf.c claimed the harmonics would be the worse in that range...still not sure how he figured that out. My oil pump nut also backed out a year later (although I'm not certain the pulley was the cause).


Other than that, it made some sweet ass torque! It was truly an impressive gain. But it's a bad idea to get one. Just get a LTW flywheel.

[matt]

(although I'm not certain the pulley was the cause).

It was. We see that all the time.

The noise was your crank bending and hitting it's bearings.

[mazur]

The noise was your crank bending and hitting it's bearings.

Oh, that makes me feel better, lol.


Well, at least it had no long term effects. Engine still makes crazy power and has great oil pressure ;)

[e30polak]

It was. We see that all the time.

The noise was your crank bending and hitting it's bearings.

:crazy: Fuck that shit!