Author Topic: removing crank damper?! (Read 3561 times)

swiss318is · « **on:** May 02, 2008, 03:56:24 AM »

what would happen if i remove the crankdamper on my non-daily-driven bmw?!
i am planning to machine some ultralightwheight underdrive pulleys out of aluminium, to reduce the force on the crank. but i am not sure if it will destroy the crankbearings, maybe???
i am not such a big fan of piston-rod-crank salad on a synthetic-oil dressing!!

swiss318is · « **Reply #1 on:** May 02, 2008, 03:56:59 AM »

there must be a reason why there is a damper!?!!?!

Cobra Jet · « **Reply #2 on:** May 02, 2008, 09:25:26 AM »

From my understanding w/ most vehicles is the dampner or commonly referred to as the harmonic balancer, is there to balance out the crank shaft and rotating assembly to prevent vibrations, premature bearing wear, etc.

Basically, if you run without it (have a bad one, or the incorrect weighted one), you have a very high chance & potential to induce catastophic engine failure - end of story.

http://en.wikipedia.org/wiki/Harmonic_balancer

Letsplayskatch · « **Reply #3 on:** May 02, 2008, 10:22:00 AM »

^^ as cobra said really. The S42 ran without one becasue it was most likely extremeley well balance from BMW Motorsport.The engines were probably put on an engine balancer - and appropriate weight shaved off the flywheel to get it all pefect. Much like the way a tyre-changer would balance you wheels by putting lead weights (or steel) on them.
In a mass-produced engine, they cant engine balance every single engine...it costs too much money. So the crank dmaper, or harmonic damper, is a cheap cost-effective way of making sure each engine falls within a certain threshhold of tolerances before it leaves the factory.
By all means remove yours, but not before having it all balanced

nuvolarossa · « **Reply #4 on:** May 02, 2008, 03:31:00 PM »

ok, but the story that the stock crank damper will crack at 7x00 rpm was not real, because Metric Mechanics revved their engines over 8000 with it, right?

EDIT: yes, they revved near 8500revs in their video of 2100 Rally engine:D

swiss318is · « **Reply #5 on:** May 03, 2008, 06:52:43 PM »

well, my crank and flywheel is perfectly balanced and every rod is balanced rotating and oszcilating (?!on english) and every piston and rod has the same weight. so i am not expecting any vibrations... i hope so..
i have to make some drawings for some nice underdrive-pulleys...

Letsplayskatch · « **Reply #6 on:** May 03, 2008, 07:24:21 PM »

have you had the whole lot balanced, as one complete unit? Thats what I mean really. CDF racing do underdrive pulleys etc, but not for out engines. however, they do make them for straight 6's, so im wondering if they can be adapted somehow...

swiss318is · « **Reply #7 on:** May 04, 2008, 04:58:30 AM »

Quote from: Letsplayskatch;48530

have you had the whole lot balanced, as one complete unit? ...

what do you mean with "the whole lot"? crank with flywheel together? or crank, flywheel and the rods with pistons? all mounted? plus the crankbolt and clutch?

Letsplayskatch · « **Reply #8 on:** May 04, 2008, 08:56:52 AM »

Yeah, with it all assembled it can then be taken for a balancing. Its then placed as one complete uint [including cylinder head, timing gear etc] on an engine dynamometer. Usually, they shave weight off the flywheel [or add to it] to get the engine as balanced as possible. Im not sure if the clutch has to be onor not though. I wouldnt have thought so.
Other means of balancing include adding/subtracting weight off the pistons or crank - but this is more expensive.

Cristian G in Oz · « **Reply #9 on:** May 04, 2008, 10:11:21 PM »

Quote from: swiss318is;48552

what do you mean with "the whole lot"? crank with flywheel together? or crank, flywheel and the rods with pistons? all mounted? plus the crankbolt and clutch?

When I did my M30 in my E12, I had the crank, Harmonic Balancer, Flywheel, clutch and pressure plate all done.
When the shop did it they took weight of all of teh above components to get them right individually then again as a "single unit".

If you want to reduce your vibes to the min you need to get all the roating stuff done together at the same time, dynamincally.

If your going to get underdrive pullys and fit them, fit them before you get the balance done. You would be supprised how a rotating mass will change when you add "a balanced" part to the end of it.

Good luck. It sounds like your going to have a screamer of an engine when it's done.

Cristian

swiss318is · « **Reply #10 on:** May 05, 2008, 05:35:47 AM »

i dont have my pistons and rods yet! mahle pistons to spec. with custom pockets for the valves and h-beam rod from bmw motorsport. when i have all parts.. we have to balance them together...

swiss318is · « **Reply #11 on:** May 05, 2008, 05:37:16 AM »

Quote from: Cristian G in Oz;48608

Good luck. It sounds like your going to have a screamer of an engine when it's done.

Cristian

thanks, and yes.. i am on the way to build a screamer!!:D to blow up all m3 and stuff..