Uffe wrote:
MACKJ wrote:
Thanks guys for all the feedback and ideas.
ChesterCRD
I cannot hear/feel the vibration outside over the normal diesel clatter.
I have actually had a very high tech vibration analysis (accelerometers and a multi channel analyser) carried out by senior vibration engineers from my work. They have said that the vibration is not normal for a diesel, in fact up to three times the vibration level they would expect for a similar output engine.
The only caveat I have on this data is that the reference standard does not mention four cylinder engines, mostly six cylinders and above. The only bit of data that they have put forward to try to determine the root cause is that the ratio of the high frequency vibration to crank speed is about 147:1. I have been racking my brain as to what could be spinning or firing(?) 147 times faster than crank speed.
147 times crankspeed at 2,000rpm is 4900Hz - that sounds like PWM switching territory to me. That vibration is really at an annoying frequency (at Vestas we use PWM at 5kHz and it is a bugger listening to it.
Do you know the frequency which the guys reported? 147 times crank sounds like turbo, but that could nearly not make such heavy vibrations are you're seeing there. Turbo would also be running at different ratios to crank speed depending on engine load. Turbos are air-pressure driven not belt driven so the ratio of 147 can't be true at all RPMs IF it is the turbo...
Hi Uffe,
Glad to see you are still hanging around. The frequency was measured at 1867 Hz. (Frequency of engine at idle was 12.67 Hz =760rpm)
Here are the accelerometer readings also;
Location Vibration level – velocity (mm/s)
Longitudinal Lateral Vertical
Front of sump 2.9 32.7 4.7
Rear of sump 2.2 31.2 2.5
Engine head 0.9 24.3 3.5
Bell housing 1.7 25.6 2.8
Transmission 0.7 22.0 1.1
Transfer case 1.4 9.9 13.9