Harmonic damper for high revs

[dsm2002]

I am starting to work out suitable harmonic dampening for a high revving M42/M44/stroker. I am currently looking at options as I plan that my stroked engine will rev to 8000+ rpms. Internet folklore suggests that over 7500-7800 revs the M42/M44 harmonic balancer or vibration damper will fail. 

I spoke with a local fella, Matthias at MH Autocare, who races a turbocharged M42 with considerable success. He has a stock balancer on his and runs it up to 7800 regularly without trouble. He does say that the harmonic needs of his tubocharged engine is less that that of a NA screamer because his turbo spends less time at these high revs.

I have located a possible harmonic damper for high rev M42s, etc. Specifically I am looking at modifying the Honda S2000 F20C damper from Fluidampr (http://www.fluidampr.com/product/530601/).  The bore ID is 30mm with a belt track OD of 140mm ... similar the M42 which is about 135mm

Fluidampr's website says it weighs 2.6kg with a rotating weight of 1.7kg, heavier than the E36 damper which is 1.5kg. For me it'd be only a guess as to what weight will be needed.





The belt drive may not line up some adjustment may be needed. In any event I'll get an engineer friend who will assist with fitting it to make up a oil pump drive mandrel to bolt on the front of the crank and could use this for a power steering pump and alternator underdrive as well.

[wazzu70]

Sounds like a good recipe for disaster. This is really not an area to guess and check in my book.

Do it proper and have ATI or fluidamper spec you out a proper one for your application.

[fumstoo]

The harmonic damper limiting the rev is a myth. If you search it here theres plenty of people running them past the "7200rpm death limit". Im not sure how that rumor was started but its been debunked time and time again. Either way, good luck!

[romkasponka]

I will make solid pulley without any dampers and I think it will last longer than I need...

[MLM]

I agree with wazzu70 on this, the masses and damping effect are related to the rotating assembly design. Stroke/ part masses etc. Not something to be guessed at. You could set up a resonance right where you dont want it.

What is the (supposed?) failure mode of the damper? Is it separation between the inner and outer ring or catastrophic failure?

[romkasponka]

Lots of engines running without any dampers. Check super-bike engines - no any dampers.... If you want to run your engine for another 200kkm maybe it will help but for racing it is useless. I checked my engines pictures library and didn't saw any factory built racing engine with harmonic damper on the crank.

[wazzu70]

Engines like the S42 did not have a damper. The I4 is a good engine structure for higher revs. The bad frequencies are down low, and as the engine hits higher RPMs it generally moves out of the bad frequency range. The I6 does the opposite due to its long crank.

Think about the rough idle on an I4 down low compared to the I6. Then think about the top end.

Race motors and motorcycle motors don't spend time in the low RPM range so its not really a concern to them. This does not mean no damper works well on a street car!

Jim Conforti started the rumor the damper would have issues above 7200 rpm, although that isnt true.

[dsm2002]

don't worry. It is not like I am just buying it getting out the grinder and drill press and hoping it'll fit. I have been in contact with Fluidampr about a specific one off damper for a stroker M42. They do not develop one-off custom dampers. They will consider a run of at least 50 due to the due to the R&D, engineering, testing damper/engine combinations and manufacturing. I have been in email discussion with Fluidampr, I told them what I am doing and they have been helpful with information so far.

I have been researching this for sometime and discussions with two damper manufacturers, a couple of engine builders (one of whom has successfully adapted a fluidampr to his race 4 cylinder which stopped it destroying blocks), a couple of race car engineers one of whom contracts for a V8 supercar and TCM race teams and the other has built Targa cars, factory race and rally cars under contract. The latter engineer will doing the work. I have the Fluidampr fit and tolerance guidelines. Adapting harmonic balancers is actually quite common in Australian and NZ where we have had to adapt in the absence of specifically manufactured products.

I have extensively read pretty well everything on the ATI website and they are not practical for me.

yep the S42 does not use a damper at all. It uses a small diameter poly-V pulley and trigger wheel. The S42 also has different crank, rods, pistons, etc. Harmonically it is very different. If only the S42 cranks, etc were cheap and I could afford the frequent rebuilds.

This is a race engine. It is not for the street. I had considered not running one but I'd like some life out of the bearings. This is an informed process.

[wazzu70]

It sounds like you have done your research so I have some hope this turns out OK.

The fitment of the damper to the crank is the simple part. Its getting the proper mass to resist torsion thats the tough part. If you are working with the company and they verify the mass of the S2k damper is adequate then you should be fine.

I know with ATI if you give them the basic specs of your engine they can figure out what damper mass you need from experience.


The guys from Aus are a crafty bunch! I work in the US for Kenworth Australia so I do a lot of work with the guys over there. They are all very handy at adapting what theyve got to what they need