[ButterRider 7]

A few things that might be the reason for the offending harmonic vibration in a diesel engine are:-
1.A bad vibration damper on the crankshaft.
2.A damaged flywheel or clutch plate.

It might be a driveline problem as well:-
3.Bent driveshaft or damaged/worn U-joint.
4.An out of line carrier bearing.

There might be many other things as well which could get out of balance and cause vibration. You should check with more than one service centres to get a good idea about it.

[Jeroen]

So the internet has spoken and basically it tells us you need to check everything and preferably replace everything too!

Now, these sort of vibrations can be really difficult to find. But hit and miss or just check everything might not be the most efficient way forward.

I noticed one more important observation you posted:

When fuel tank is full, vibration intensity reduces to the minimum. Could this is because of damping due to fuel weight? As fuel tank becomes empty vibration intensity increases. Or, is it something to do with fuel pressure?

Nothing to do with fuel pressure, this is about fuel weight and thus mass and thus a different resonance frequency. You need to hone in on this as it is, next to your first measurement a very concrete data point.

Remember my first remark based on your measurements? Pointed towards body panels, but of course a fuel tank is just panels as well. Or there could be some interaction between a body panel vibrating and the the fuel tank. When that fuel is full, it vibrates less or not at all . I understand it happens at stand still too? So you can just walk around the car, put in on a ramp and get underneath.

So I would take a very close look at the tank, with low fuel, run the engines revs up to where it the noise start. Feel the fuel tank, does it vibrate. or is there a part or connection that vibrates, is it in touch with a body panel or something else it should not. Most fuel tanks have some sort of metal straps that hold them down with rubber mounts. Are they still ok.

With these problems you really need somebody who knows what he/she is doing. Starting to replace stuff is not necessarily a show of confidence in this case. With these sort of problems a good mechanic might spend several hours, looking and feeling before coming to any conclusion.

Good luck.

Jeroen

[IP_Man]

Originally Posted by Jeroen

Nothing to do with fuel pressure, this is about fuel weight and thus mass and thus a different resonance frequency. You need to hone in on this as it is, next to your first measurement a very concrete data point.

Remember my first remark based on your measurements? Pointed towards body panels, but of course a fuel tank is just panels as well. Or there could be some interaction between a body panel vibrating and the the fuel tank. When that fuel is full, it vibrates less or not at all . I understand it happens at stand still too? So you can just walk around the car, put in on a ramp and get underneath.

First, those vibrations do not rattle any body parts of the car. Secondly, I don't think it is generated by body panels. Vibrations are originating from engine that vibrates entire car.

I believe, full tank reduces vibrations not due to weight but due to viscous movement of the liquid fuel.

At standstill, due to nil load on the engine, vibrations are less but with load, they get amplified. It is difficult to simulate this situation when car is at standstill. Solution is to test car on chassis-dynamometer that can put variable load on the engine at select RPM (1000 in our case) value.

[Jeroen]

Originally Posted by IP_Man

First, those vibrations do not rattle any body parts of the car. Secondly, I don't think it is generated by body panels. Vibrations are originating from engine that vibrates entire car.

I believe, full tank reduces vibrations not due to weight but due to viscous movement of the liquid fuel.

At standstill, due to nil load on the engine, vibrations are less but with load, they get amplified. It is difficult to simulate this situation when car is at standstill. Solution is to test car on chassis-dynamometer that can put variable load on the engine at select RPM (1000 in our case) value.

As the vibration and sound are audible when the car is at standstill it is obvious that it is the engine that somehow causes the vibration. A car with all its components is one big complex system. Each component has its own vibration characteristics and natural resonance. And they all interact with each other;

Many members will recognise the following situation. A car, with engine at idle. The engine runs perfect and smoothly, but your rearview mirror is still vibrating. It is the only part that is vibrating. Unlikely you would change the engine mounts to see if that would stop it vibrating. You would check its mount, rubbers, connection, bolt, nut. If the worse comes to the worse add weight to it.

Even with brand new engine mounts and balancers and whatever, there might be the odd frequency where something is simply starting to vibrate. You should also bear in mind that the engine is also connected to a host of other parts that also connect back to the chassis and other parts of the cable. Think hoses, pipes, cable harnesses etc.

You have something similar. Somewhere you have a part that is vibrating. We do not know which part, but we do know that the amount of fuel in the tank changes the vibration. Vibration, or more importantly, a parts resonance frequency, depends on its mass. By adding fuel into the tank you are changing the mass of the tank and therefor its resonance frequency. In addition the mass increase the weight of the fuel tank, so it also is likely to push more firmly in its mounts.

So either the fuel tank itself or something in its immediate vicinity must be causing the vibration.

I am not sure what you mean by viscous movement of the liquid, or how viscosity relates to vibration/resonance. It is mass that affects an objects resonance frequency, not viscosity.

So far the fuel tank is the only clear clue where the vibration might be coming from. So I would start looking there, find what is vibrating in or near the fuel tank and work my way down. It could be as simple as a rubber mount being loose. Or like the rearview mirror a fuel line resonating and it might even get amplified by the (empty) fuel tank.

Your fuel tank has several openings and connections in it. Several pipes, probably a filter and or pump inside or nearby. Some cables, connectors, some float mechanism to indicate the fuel level etc etc. All these bit and pieces, in combination with others can easily cause this. The good news; once you have access, easy to see and feel what is going on!

Would be great to get it onto a dyno, to simulate load and increase the vibration, hopefully making it easier to find what is causing this.

Here for a sobering thought: My (Naval College) graduation thesis in 1979 was called "Prediction of sound levels during a vessel design phase". I was trying to predict vibration levels throughout a ship in (and thus sound levels) through a very rudimentary computer model during the ship design phase.

Vibration and sound predication and elimaniation in all industries has come a very long way since. We are talking forty years! But finding that one rattle in a car, a bike or a ship can still be a huge undertaking. But the approach has not changed.

Good luck

Jeroen

[IP_Man]

Originally Posted by Jeroen

I am not sure what you mean by viscous movement of the liquid, or how viscosity relates to vibration/resonance. It is mass that affects an objects resonance frequency, not viscosity.

So far the fuel tank is the only clear clue where the vibration might be coming from. So I would start looking there, find what is vibrating in or near the fuel tank and work my way down. It could be as simple as a rubber mount being loose. Or like the rearview mirror a fuel line resonating and it might even get amplified by the (empty) fuel tank.

I agree, 'viscous' is very appropriate word, what I meant was inertia of the liquid fuel make it excellent damping system for the vibrations.

As per your and others suggestions, we will ask service advisor to look in to fuel tank rubber mounting and ladder frame to body mountings.

I'm still not very clear actual root cause of the vibrations. Safari Storme VX (varicore-400) don't have vibrations peaking at 1000 RPM. It uses same ladder frame, fuel tank and passenger body. Something has changed in the engine that solved this problem.

TATA is unable to give corrective solution to this problem because of which, my friend has filed complain in consumer court.

[IP_Man]

Sorry for back to back post.

I need urgent advice.

My case is in final stage in consumer court for this issue (took two and half years and still it is going on)

Opposite parties i.e. TATA Motor is asking for certification from government approved automobile testing agency for this problem.

Any input? From where can I get certificate?

I know from my limited knowledge that it will require dynamo to put load on the engine to measure vibrations at different RPM.

Any help in this matter is appreciated.

[SPIKE ARRESTOR]

Originally Posted by IP_Man

Opposite parties i.e. TATA Motor is asking for certification from government approved automobile testing agency for this problem.

Any input? From where can I get certificate?

Sorry I could not find this info, what test do you need to get done? Based on where you are located, you could try with ARAI, VRDE, GARC etc. Why can't TATA motors test it in one of the Govt Agencies and prove that the 'problem' doesn't exist, the test could be conducted in your presence. May be if you could tell me what is to be tested, I could guide you better.

As far as Chassis Dyno is concerned, even some good educational institutions / private entities have this facility. I would suggest, if you can get the test done outside, get the preliminary results and then go to a Govt Agency for a confirmatory test. If the problem is repeated in both cases, then you have a strong case in hand.

Spike

[IP_Man]

Originally Posted by SPIKE ARRESTOR

Sorry I could not find this info, what test do you need to get done?

I thank you for the guidance.

My case is against TATA for the offending vibrations that peaks just after idle RPM i.e. 1000. This makes driving in the city painful as RPM middle frequently cross 1000 in bumper to bumper traffic.

They are certainly from unbalanced rotating mass as they occur in driving and coasting, whenever RPM needle crosses 1000.

As per your suggestion, I will try to contact ARAI or VRDE but I don't know whether they will entertain a small customer like me.

On the other hand, you correctly pointed out why TATA is not disproving me? They won't because they know this problem does exist.

[SPIKE ARRESTOR]

Originally Posted by IP_Man

As per your suggestion, I will try to contact ARAI or VRDE but I don't know whether they will entertain a small customer like me.

If they don't agree, there is a solution for this as well:

1. You could request (prayer in your petition) to the Court to give an order giving you permission to conduct the test at a certification center of your choice, in the interest of justice. In case your argument fails, the costs for the test would be on you, if you prove your point, then the OEM pays the costs for the test.

2. The court could order the OEM to conduct the test in your presence and share the results, findings, observations. For an OEM this is a pretty routine test and can be performed by them without much effort.

This test could be performed even without a chassis dyno as it is easily reproducible, which any OEM worth its salt should be capable of. Also, as I believe this is a civil case, the case needs to be proved following the "preponderance of probability" and not "proof beyond reasonable doubt" principle, do keep that in mind. Since you are dealing with a scientific phenomenon, the result should be sufficient.

However, I would add a small warning when route 2 is taken. OEMs perform hundreds of different tests daily with certifying agencies, so they know how the system works and the responsible people involved, I hope you understand my point.

All the best.

Spike