Author Topic: What does the harmonic balancer do? (Read 4825 times)

martin347 · « **on:** April 01, 2008, 11:08:11 AM »

As title. Has anyone removed it?
I am using the m44 block and crank and am changing to aftermarket ecu. So I am going to use the trigger wheel off the crank (internaly). Therefore I could bin off the trigger wheel at the front.
I am also going to be increasing the rev limit to approx 7800rpm (an increase of 20%). So I will be decreasing the front pulley, to drive the water pump and alternator, in size by 20%.
I am sure some people will say that this is risky and I would appreciate there opinions, but I would like you to consider that the original crank pulley measures 150mm in diameter. The pulley for the PAS pump measures 120mm (20% less than the w/p pulley) ie the size I will be reducing it to. This pulley doesn't go through the harmonic balancer and is bolted straight to the crank. So does this not prove that the water pump/alternator belt could be run through a pulley 20% smaller, bolted straight to the crank?
Any opinions would be gratefully appreciated.
Thanks, Martin.

strypt · « **Reply #1 on:** April 01, 2008, 01:16:17 PM »

Every ignition event creates a frequency in the crankshaft. Of coarse the frequency will vary with the engine rpm (more ignitions/time unit) and if the actual frequency concurs with the resonance frequency of the crankshaft there will be quite large forces acting on it and if unlucky it breaks. What the harmonic balancer does is move the resonance frequency up, or down, in rpm range to get it out of the engine operating range.

I would think twice before removing it, I'm not saying that it won't work (I don't know, haven't tried) but also consider what happens with your (expensive modified?) engine if it does break.

Paul Strefling · « **Reply #2 on:** April 01, 2008, 02:15:13 PM »

The rev limit on most motors is dictated by the valve train, most significantly by the accelerations of the valve train mass which is dictated by the cam profile.The safest way to increase your rev limit is by keeping the ratio of rpm/(mass of (valve+spring+lifter)) greater than that of stock. A second way of safely increasing the rev limiter is by of course running stiffer valve springs.

D. Clay · « **Reply #3 on:** April 01, 2008, 11:54:49 PM »

http://m42club.com/forums/showthread.php?t=2320
The danger of the removing the harmonic balancer is that the crankshaft cracks. As noted above, may or may not happen.

martin347 · « **Reply #4 on:** April 02, 2008, 01:39:25 AM »

Thanks, thats an interesting thread. And I do realise I need to do something with the valve train aswell. I am already looking into that and want to find a set of euro spec s50 lifters.
But it doesn't go into anything about the harmonic balancer. I would really love to find some evidence that removing it will be a mistake (I don't really want to be the one to prove it!).
Why do no other engine manufactures use them (with some exeptions)?

nicknikolovski · « **Reply #5 on:** April 02, 2008, 02:32:51 AM »

The harmonic balancer absorbs vibration caused from the engine's forces.
Removing it will most likely create more engine noise. I would just leave it the way it is.
I recommend just strengthening the valvetrain, eg titanium valves, BMW Motorsport springs, etc. If you have the money you can even buy already strengthened reconditioned cylinder heads complete ready to be installed.

Check out http://www.vacmotorsports.com
It is an awesome website for BMW Performance.

martin347 · « **Reply #6 on:** April 02, 2008, 02:54:41 AM »

Quote from: nicknikolovski;45913

The harmonic balancer absorbs vibration caused from the engine's forces.
Removing it will most likely create more engine noise. I would just leave it the way it is.
QUOTE]

I have no problem with more engine noise- its a rally car.

strypt · « **Reply #7 on:** April 02, 2008, 05:48:31 AM »

Quote from: martin347;45912

I am already looking into that and want to find a set of euro spec s50 lifters.

You can stop looking as they won't fit. The diameter is too large and the "holes" (don't know the english word for it sorry) in the engine cannot be made large enough to accomodate them. Cheapest way is to modify the hydraulic ones by removing the pin in the middle and replace it with a solid one, or if money is no problem just buy them from for example catcams.

Paul Strefling · « **Reply #8 on:** April 02, 2008, 06:17:53 AM »

You can always run the VW lifters as well, they are considerably lighter that the BMW ones.

Boyracer · « **Reply #9 on:** April 02, 2008, 08:50:38 AM »

Quote from: strypt;45918

You can stop looking as they won't fit. The diameter is too large and the "holes" (don't know the english word for it sorry) in the engine cannot be made large enough to accomodate them. Cheapest way is to modify the hydraulic ones by removing the pin in the middle and replace it with a solid one, or if money is no problem just buy them from for example catcams.

Thank you for the S50 lifter info, I have been thinking about it myself.

Most likely I will just convert stock lifters to solid operation, cheap and quick solution

martin347 · « **Reply #10 on:** April 02, 2008, 10:20:35 AM »

Quote from: strypt;45918

You can stop looking as they won't fit. The diameter is too large and the "holes" (don't know the english word for it sorry) in the engine cannot be made large enough to accomodate them. Cheapest way is to modify the hydraulic ones by removing the pin in the middle and replace it with a solid one, or if money is no problem just buy them from for example catcams.

Yeah, thanks for the info. That may have saved me afew ��or$$$!
But back to the harmonic balancer, can anyone give me a 100% reason why I can't run the engine without it?

Cobra Jet · « **Reply #11 on:** April 02, 2008, 12:32:57 PM »

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

strypt · « **Reply #12 on:** April 02, 2008, 01:56:42 PM »

Quote from: martin347;45942

Yeah, thanks for the info. That may have saved me afew ��or$$$!
But back to the harmonic balancer, can anyone give me a 100% reason why I can't run the engine without it?

No problem. You might want to check the VW Golf's between 75-83 -ish, I believe they have solid lifters that fits but I don't know for 100%.

Don't you accept my explaination?

Was apparently even listed at wikipedia, do you believe it now??

martin347 · « **Reply #13 on:** April 02, 2008, 03:22:39 PM »

Quote from: strypt;45965

No problem. You might want to check the VW Golf's between 75-83 -ish, I believe they have solid lifters that fits but I don't know for 100%.

Don't you accept my explaination? Was apparently even listed at wikipedia, do you believe it now??

ok, thanks. i'll have a look through them.
Yes, I have now excepted your explanation and quite afew others! I just felt like I needed it explaining properly, so I new in my own mind that it wasn't possable.
I feel like I still need to do something with the pulley ratios if I am going to rev higher. Which looks like it could be making larger water pump/alternator pulleys instead and buying a genuine BMW harmonic balancer from the stealer!
I will now concentrate my efforts on lightening the valve train.
Thanks for all the replys, Martin.