45 replies to this topic

[ads7]

Just about to swap in 'oe spec' engine mounts from minispares, which raises a question in my mind.

Being far thinner than those used in the Metro they transmit a lot more vibration.

Has no one ever modified Mini subframe to take thicker rubber mounts by turreting the subby mounting point down/outwards? Surely this would contribute to a much lower cabin noise?

Its years since I rode in an a series equipped metro but recall them being quiter than a mini

Edited by ads7, 13 November 2020 - 08:40 PM.

[mini-mad-mark]

I had an early A series metro and as I recall the mountings are completely different to a mini - at the clutch end the mountings are fitted fore and aft of the housing on brackets rather than a single on the end  - at the other end there was a long ally bracket with two mountings, so basically four rubbers instead of two which may be why the metro was less noisy? Also no bulkhead stabiliser IIRC so no noise directly transmitted to the bulkhead cross member which might be a real noise generator in a mini - I assume the fore and aft movement was controlled by having fore and aft mountings at the clutch end.

 

My wife had an Allegro years ago - that had two tie bars to the bulkhead but seemed less harsh but don't recall what the actual engine mounts were like

What about Austin 1100/1300 think the clutch end was similar to a mini but the other end was fore and aft on the timing cover I recall so maybe why it felt a bit more civilised (as far as I recall - my mate had one for 2-3 years when we first started work)

 

If you want a NVH controlled car probably best to skip the mini....

[ads7]

Haha yes these type of discussions normally conclude along the lines that Minis are just noisy, however I do think that thicker lower engine mounts alone would make a real improvement and wouldn't be hard to engineer.

[Homersimpson]

Haha yes these type of discussions normally conclude along the lines that Minis are just noisy, however I do think that thicker lower engine mounts alone would make a real improvement and wouldn't be hard to engineer.

You could probably use an automatic front subframe to get more room as they are wider between the engine mounts.

 

Seems like a lot of work for very little gain though to me.

[KTS]

here's a recent example of the subframe mounts being modified.  in this case it's to lower the engine

 

http://www.theminifo...39#entry3629419

[Ethel]

On the flip side, softer mounts means more movement & there was much less space for that under a Mini bonnet, even compared to a Metro.

 

Though all tranny A models used near identical gear change linkages requiring a similar degree of wobble resistance.

[nicklouse]

Haha yes these type of discussions normally conclude along the lines that Minis are just noisy, however I do think that thicker lower engine mounts alone would make a real improvement and wouldn't be hard to engineer.

Back in the day the subframes went to rubber mounted to reduce the noise transfer.

 

your first problem will be finding some mounts to use. And then how to attach them to the power unit.

 

it is easy to make mounting systems to fit another power unit with different mounts but to make changes to the existing set up and mounting points is not going to be easy and for little reward.

 

back to the Metro the engine is on 4 mounts as does not need a stabiliser. And the subframe only has 4 mounts which are of a tubular design.

 

if you really want to reduce the noise spend the cash on materials to absorb it.

[Bobbins]

In my experience the best way to reduce vibration from the engine is to have the engine properly balanced, if not doing the whole crank assembly just the flywheel and clutch assembly will be a major improvement. After that it’s engine noise reduction via sound proofing.
The NVH aspect of a Mini is never going to be great but it can definitely be improved.

[Dusky]

The engine mounts dont transmit a lot of vibrations. The engine steadies is where the money's at.

[ads7]

The engine mounts dont transmit a lot of vibrations. The engine steadies is where the money's at.

Interesting. I'd read elsewhere that swapping cheap (apparently hard from new) mounts for Minispares oe spec items which are softer off the shelf made an appreciable reduction in NVH, I guess everyone's experiences vary. I'm due to do exactly this. The proof is in the pudding and I'll find out for myself when I swap in the new mounts.

I see a lot of sense in the engine stabiliser transmitting vibration, doubt very much that can be remedied though?

I'll be making numerous improvements in sound deadening, rubber as opposed to poly mounts on subby etc and I'll do a small write up when I feel I've done enough.

Thanks everyone for your thoughts.

[sonscar]

Not Mini related but on my Triumph TR7 I changed the gearbox mount and the increase in harshness is very noticeable.Look at modern car engine mounts and marvel at their size and complexity.Gains could probably be made but you would have to be cleverer than me(this would not be hard) ,Steve..

[ads7]

Cleverer than me as well! I'm sure someone could pull it off.

Meanwhile I'm getting serious..well fairly. I've just bought a noise meter to measure improvements after every part is fitted. Will be doing a YouTube video or two on the experiment as I reckon the subject of NVH is a continual bugbear

[Cooper Mac]

Having worked in NVH, I'm interested to see how this progresses.

 

ads7, what sort of noise meter have you bought? Is this a handheld meter, or can this be plugged into an analyser to record and play with the results? Recording and comparing noise readings is difficult unless you have access to an anechoic chamber. If you are recording the noise as you drive, then this is difficult from within the car, because of it's size and the reverberation of everything inside the car. You would also need to have all parameters exactly the same on every test, speed, engine revs, position of noise meter, what you wear!

 

Changing the engine mounts might make a difference due to different grades of materials etc, but it will generally be what the mount is bolted to (the subframe) that will determine the audible noise. In the case of the top engine steady, the noise is amplified by the fact that the steady is fixed to the bulkhead, which acts as a sounding board. The 'sound' from this mount is reduced by fitting OE bushes as these are softer and therefore damp the vibration seen at the bulkhead, less vibration of the sounding board = less noise. If you put poly bushes in this top mount, the vibration is damped less, and therefore transmits more vibration into the bulkhead sounding board = more noise.

 

Unless you have already done it, I think fitting sound deadening to the bulkhead would be the first thing to do to damp and change its natural frequency.

[sonscar]

What about fluid filled mounts as used by Sierra Cosworth motors,standard Sierra mounts were horrendous when fitted to the Cosworth engine?Steve..

[ads7]

Having worked in NVH, I'm interested to see how this progresses.

ads7, what sort of noise meter have you bought? Is this a handheld meter, or can this be plugged into an analyser to record and play with the results? Recording and comparing noise readings is difficult unless you have access to an anechoic chamber. If you are recording the noise as you drive, then this is difficult from within the car, because of it's size and the reverberation of everything inside the car. You would also need to have all parameters exactly the same on every test, speed, engine revs, position of noise meter, what you wear!

Changing the engine mounts might make a difference due to different grades of materials etc, but it will generally be what the mount is bolted to (the subframe) that will determine the audible noise. In the case of the top engine steady, the noise is amplified by the fact that the steady is fixed to the bulkhead, which acts as a sounding board. The 'sound' from this mount is reduced by fitting OE bushes as these are softer and therefore damp the vibration seen at the bulkhead, less vibration of the sounding board = less noise. If you put poly bushes in this top mount, the vibration is damped less, and therefore transmits more vibration into the bulkhead sounding board = more noise.

Unless you have already done it, I think fitting sound deadening to the bulkhead would be the first thing to do to damp and change its natural frequency.

Thanks for your professional input that's absolutely invaluable.

Just using a cheap noise meter measuring decibels.

I was going to run the car in fourth gear at around 52mph where the resonance is at its worst (just wiring in a rev counter to give more accuracy) on the same stretch of road after each change/mod with weather as similar as possible given the British climate.
Imperfect, but some controls in place.

I've just ordered one piece mpi spec engine steady rubbers.

Would filling the bulkhead cross member with expanding foam help reduce noise to any degree?

I'm running solid top front subframe mounts which will revert to rubber.

Free flow tubular manifold is fitted and will have exhaust wrap applied.

I've already fitted closed cell 10mm foam to the majority of the bulkhead, expect I'll need to add extra soundproofing to compliment this.

So an imperfect experiment. Any more helpful suggestions much appreciated as I'd like to help people address the problem effectively within the constraints of a modest budget.

Thanks Adam

Edited by ads7, 16 November 2020 - 10:27 PM.