9 replies to this topic

[alpder]

My Mk2 estate is finished*. Drives lovely. But lots of engine noise in the interior. Great if you don't want conversation. But it is a bit tedious, having to put in earplugs just for a trip to the shops.

 

I've changed the cone filter for an original airbox ('swiss-cheesed' and with K&N). That makes a huge difference. But there's still plenty of other engine noise.

 

I don't much like soundproofing felt and thick carpet - it holds moisture, makes maintenance harder, and (under the bonnet) is a fire risk. But clearly I do need some. Currently there's 4-way stretch almost everywhere inside (roof, walls, front arches, bulkhead, inside the doors). And there are none of the original interior trim items/panels - everywhere it's just plain metal with 4-way stretch.

 

Not after a modern driving experience, just something that sounds a bit less like the end of the world. Are there a few pieces of off-the-shelf sound-proofing that make the most difference, when added? Would changing the engine-steady rubbers (top and bottom) from poly to olde-worlde rubber make significant difference?

 

*Of course it's not "finished". Is any Mini, ever?
 

[KTS]

unfortunately to keep the noise levels down means you'll need a combination of materials to deaden low frequencies and absorb the higher frequencies

 

At a minimum, you should consider something like dynamat or silent coat on the large panels (roof, door skins, quarters, bonnet etc) to cut down panel resonance

 

you may not like underlays, felts and carpets but they are very effective at both adding mass (which will help to deaden) and absorbing noise 

[PoolGuy]

If I was only allowed to use one product, it’d be Dynamat Superlite on the floor, bulkhead and doors.

[Steve220]

Mass loaded vinyl is the king, but it goes in hand with closed cell foam to be very effective

[Bobbins]

Soundproofing and deadening is very much a case of incremental gains, you need to address a lot of areas and with differing and appropriate products to make a noticeable difference. If you’re looking for a single solution start with a thick piece of soundproofing material on tne engine side of the bulkhead and sound deadening in the cabin above the toe board area … sorry that’s two! Also don’t underestimate what comes through from the exhaust. Oops that’s three!!

[alpder]

Thanks everyone. I'll tackle some engine-bay bulkhead insulation. I see there's a £20 item from MS that just fits so I'll start with that. And then add some home-grown toeboard insulation after I've found and cured *all* the water leaks in that area - so that's 'one day never' then

[nicklouse]

The correct air filter.

[rock1day]

I read once that a lot of noise comes from the bulkhead box section (at the top of the toe board) that opens into the passenger footwell. Perhaps blocking up the hole with foam may help?  

[alpder]

Making a start...

 

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[alpder]

For those curious how this turned out...

 

This Mini Traveller (with GRP upper rear van sides) has now had 1.3mm KilMat installed on the doorskins, the door pockets, the rear lower side panels, the bulkhead (above the shelf only) and the shelf itself. The floors have had 3.5"-wide strips stuck full-length along the tops of all the ridges. The original carpet / 4-way-stretch was laid / glued back over the top of the KilMat afterwards.

 

The roof and the upper rear side panels haven't been treated (yet) due to the considerable work of recarpeting them after. And the lower bulkhead/toeboard/interior wheel arches haven't been done because their shape doesn't really allow them to resonate anyway. The spare wheelwell and the area around it are too fiddly to treat. If I was to treat the roof in future, I'd probably stump up the extra for Dynamat just in that area, in the hope that the extra £££ would buy me the strongest and most heat-resistant adhesive.

 

KilMat applied onto bare paint sticks well. On tricky surfaces, a light application of spray adhesive massively improves adhesion.

 

The effect is impressive. The noise - in what was virtually a bare car - used to be apocalyptic. It was ear-damage-inducing even with ear-plugs plus ear-defenders. Now it can be driven on short trips with no hearing protection. And on longer trips a pair of foam earplugs makes it quite comfortable. No doubt doing the tunnel and the remaining large panels, and adding plenty of underlay on the floor, would make another big difference. But this is good enough for my needs. And anyway there are massive sound-passages in the bulkhead (the plastic speedo cowl and flexible fresh air pipe) through which plenty of engine noise can penetrate, so there's a hard limit on how much difference treating the panels can make.

 

I bought 50 sq ft of the KilMat. About 1/3rd of it is left over - which should be enough to to do the upper rear side panels when I get around to it. Amazon seemed to be the cheapest place to buy it. KilMat is about half the price of Dynamat and comes in two thicknesses - I used the thinnest. A roll of aluminium sticky-back tape is useful for covering joints and edges, so the black butyl can't bleed through the 4-way-stretch glued on top of it. And a small application roller (say 1" width) makes bonding it much easier - though a 1" putty-knife can be used instead, with care, to get similar results.

 

If the KilMat adhesive fails in this summer's heat (dream on) I'll update this thread.

Edited by alpder, 12 April 2024 - 09:16 PM.