im really curious also about how the associated sound is being generated. i got in the car before and really slowly brought the rpms up, and really paid attention to where it starts. right at 1500 you can actually start to feel the vibration, but it is not as severe at that speed. also at that rpm the noise accociated is the most prominent. at 1500 i can feel the vibration, but it is not steady. it has a "beat" to it, it comes like once every half second. then as i bring the revs up a bit higher it pretty much dissapears till a hair over 2500 where it starts again and becomes worst at 3000. notice anything here? 1500 + 1500 = 3000. i cant tell cause after a bit over 3k its too hard to feel but i bet its there at either 4500 or 6000rpms as well. try this guys, everyone who has this please try and report back. put the car in neutral and very slowly bring up the rpms, really pay attention to where you feel/hear it and at what rpm
Yes, I realized before, that the first vibe is somewhere at 1500 rpm and the second after 3000 rpm... but the biggest news is, that I tried today at work and got those same 3200 rpm vibrations on a 2006 Range Rover with 4.4 liter V8! That luxury car has almost no vibrations from the road surface through wheels, not to mention from the drivetrain/engine. But bringing the revs up at standstill brings the vibration to the body exactly at 3200 rpm... Are we talking about characteristics on big V8 engines, that for some reason are transfered to the body in our cars more stronger?
When I started reading this thread I had a suspicion, that it is so called secondary resonance vibration (excuse me if i didn't name it correctly, it was long time ago i've read about it)
Basically any engine has those vibrations, but for example in 4 cylinder which is already so unbalanced you don't feel it as much cause it's shaking all the time anyway.
For example on my mondeo, i've got 2.5 litter V6, and I can easily get the same sort of vibrations at about just over 2000 revs, it's just at a different rate (i.e. faster), the engine starts sounding as if it run out of oil. Mind you, one feels it only if at a stand still brings the revs slowly up, and then at above 2000 rpm you feel the very same vibration.
This situation leeds to engineers adding the counter-balancing shafts which do reduce lots of vibrations from the engine, for example in mondeo's V6 there are 4 and it is the smoothest engine i've ever heard. apart from this little spot just over 2000 revs
Also one of the most naturally balanced engines is a straight six, and that was the reason why BMW and Mercedes were using it in all their cars (and 4 cylinder budget engines of course) before the end of 80s when they started all this v8 and v12 madness. strictly saying v12 is more naturally balanced engine as it's two straight sixes together, v8 though is not an ideally balanced engine at all as it is two straight 4-cylinders together.
The reason that it appears on certain revs is that many different rotating parts (rotating at a different speed) at a certain point get into resonance with each other, hence why that vibration and sound do not match any rotating component's speed in the engine. And that's why Valkman could easily find this vibration on the range rover's v8 - cause they all (not range rovers, engines i meant
) have it. That's why you get it on 1500 RPM and then at 3000 RPM - certain rotating parts get into resonance with each other. Of course you probably will not feel it at 4500 and 6000 as the vibration is faster than what you would register. The very same thing for example with a disbalanced wheel - itis the worst at around 70 mph, and after let's say 100 mph you don't feel it anymore (does not mean it does not vibrate though)
It's just that with ageing or worn out engine/tranny mounts this sound and feeling can be amplified, compared to a new car, where everything is new and isolates this vibration from the driver much better. So the conclusion is to change all the engine/tranny mounts and it is going to reduce significantly the vibration, and nothing much you can do i guess...
Engines vibrate:M5launch: sorry if my mumbling is no help
Regards,
Tony