Engine harmonics

[m3f_98M3csm]

Guys,



Does anybody know the most likely cause of unusual engine harmonics? I assume either the dual mass flywheel, the harmonic balancer OR serious internal engine damage. Vibration is rpm dependent. Car is 98, has 140k, everything new on motor except bottom end, cams, valves, and timing chain. Car pulls hard and has m50 manifold with trm tune (problem was pre-existing). I drive it hard very frequently + some autoX.



Any insight is appreciated.

[m3f_Danwilz]

Guys,



Does anybody know the most likely cause of unusual engine harmonics? I assume either the dual mass flywheel, the harmonic balancer OR serious internal engine damage. Vibration is rpm dependent. Car is 98, has 140k, everything new on motor except bottom end, cams, valves, and timing chain. Car pulls hard and has m50 manifold with trm tune (problem was pre-existing). I drive it hard very frequently + some autoX.



Any insight is appreciated.

Let me guess around 3k rpm's in neutral?

[m3f_Braymond141]

Is it bad enough to shut cylinders off?

[m3f_englishtom1596q]

most vague post ever. How about the rpm's that you're feeling it? motor mounts installed etc.


The S52 is a very unbalanced motor which people speculate is the reason oil pump nuts back off. Still interested if the VAC harmonic dampener fixes this. Once I put poly motor mounts in i get a lot of vibration around 3K but this seems to be the usual.

[m3f_98M3csm]

Let me guess around 3k rpm's in neutral?

Lol, yes that is the most prominent weird vibe..

Is it bad enough to shut cylinders off?

No, Im only concerned because I know my s52 was not this way when I acquired the car.

most vague post ever. How about the rpm's that you're feeling it? motor mounts installed etc.

It occurs at various times in the rev range, around 3000 being the most obvious. Motor mounts are OE and have about 10,000 miles on them. recent plugs, all 6 coils, CCV, O2s, fuel filter, all vacuum lines checked or replaced. Everything seems to be functioning perfectly except for vibrations that didn't exist a couple years ago.. And they feel like the result of imbalance.

[m3f_englishtom1596q]

its probably your newer motor mounts. mine had the vibration with stock mounts but wasn't really noticeable. once i upgraded them you feel EVERY vibration through the cabin lol In your case nice fresh mounts probably haven't loosened up yet

[m3f_98M3csm]

its probably your newer motor mounts. mine had the vibration with stock mounts but wasn't really noticeable. once i upgraded them you feel EVERY vibration through the cabin lol In your case nice fresh mounts probably haven't loosened up yet

Well thanks for your input. I guess I'll just believe that it's fine. I'll be putting a new clutch in it before too long. I guess I'll fork out the dough for a brand new dual mass flywheel (like they say you should) and see if that changes anything.

[m3f_Alex Lipowich]

The S52 is a very unbalanced motor which people speculate is the reason oil pump nuts back off.

My understanding is that it is the lack of an oil chain tensioner. Oil chain tensioned engines less likely to have this problem.



Look at true S Engines for an improvement here.



Eh, just what I heard around the campfire.