21 replies to this topic

[Pickwah]

Hi all

Since the install of my freshly built 1330 I've spent so much as a small fortune trying to lower the cabin noise mostly coming from the engine. I've done the basics just as fitting a second silencer to the exhaust and fitted an original airbox. The car is lined with silent coat and has a sound-proofing felt kit under the carpets. I went as far as fitting a dash, still with no success.

My problem starts when cruising along at say 60mph.. the engine tone starts to become unbearable!

What can I try next?

Anything considered as I'm driving 400 miles to Cornwall before the IMM.

Many thanks
Matt

[KTS]

engine noise or exhaust noise ?

 

have you blanked off/sound proofed the hole in the bulkhead behind the carb ?  depending on carb/filter setup induction noise can be very loud

 

if all else fails, get some earplugs for your trip.  probably the least cost and most effective solution.

[Pickwah]

The bulkhead has a felt kit on the engine side and a scratty old foam bulkhead liner on the interior side. Thinking of lining the entire front of the car (behind heater etc) with 10mm closed cell foam?

[KTS]

..is it the heavy, technicolour foam liner, and both bits (upper (dash) & lower bulkhead) ?  that performed pretty well as i recall

 

do you have carpets and underlay ?

 

not used closed cell liner so no idea how good it is - there must be a few topics on here about that though

 

as above, lots of noise comes through the bulkhead speedo hole, so make sure that's nicely padded out with material (..if you have a centre speedo just watch you don't knock out any bulb holders while you're doing it..)

[Steve220]

Bitumin pads are only a small part of sound deadening. It's frankly almost useless on the bulkhead as it's a stiff panel. Closed Cell foam and heavy mass vinyl are where you're going to get the best results on places like the bulkhead and floor pan.

[unburntfuelinthemorning]

A bit of work but a higher final drive ratio should help.

[Curley]

I doubt felt is really going to help with the sound levels I think you're after. Bitumin/Dynamat/Silent Coat help dampen sound by changing the resonance frequency of vibrations (and thus does not need 100% coverage to work). Only thing that's going to stop noise is physical mass. Instead of a single 10mm foam consider layering different densities of foam to make up your 10-12mm thickness. 

 

I suspect much of the noise you hearing not coming from the engine. Would be worth a visual inspection of all the bushes & mounts for excess play. Obviously the more solid mounts fitted the greater the NVH you'll experience & more mass you'll need to add to absorb it.

 

If its a Rolls Royce type of silence you want think about doing the front inner wings, bulkhead, rear arches, seat base and if possible the floor with the same sandwich.

Edited by Curley, 18 August 2019 - 06:46 PM.

[Chris1275gt]

I've put a layer of thet felt type insulation then 10mm closed cell self adhesive foam on the entire front bulkhead inside the cabin including behind the dash, with carpet on top of that and vinyl between the top and bottom rail On the n/s there is a hole under under the lower shelf to accommodate the LHD pedal mechanism I filled that with a bit of fibreglass and either on side of the pedal mechanism. In the engine compartment I covered the whole bulkhead with 10mm closed cell heat resistant self adhesive foam and on the top half of the bulkhead I put the vinyl sound reduction kit on top of the foam the noise was significantly reduced to an acceptable level for a mini.

[Curley]

I've put a layer of thet felt type insulation then 10mm closed cell self adhesive foam on the entire front bulkhead inside the cabin including behind the dash, with carpet on top of that and vinyl between the top and bottom rail On the n/s there is a hole under under the lower shelf to accommodate the LHD pedal mechanism I filled that with a bit of fibreglass and either on side of the pedal mechanism. In the engine compartment I covered the whole bulkhead with 10mm closed cell heat resistant self adhesive foam and on the top half of the bulkhead I put the vinyl sound reduction kit on top of the foam the noise was significantly reduced to an acceptable level for a mini.

#properjob

[Alice Dooper]

We rebuilt our car as a long road trip easy cruiser and after fitting a works s head / exhaust etc we need3d to go an extra bit so we -

1. Dynamat on inside of bonnet, you only need 40% coverage , then foil backed heat resistant sound absorbing foam on the inside of the bonnet. Wasn’t overly impressed with the foam but it does work a bit.
2. 25mm closed cell foam on upper engine side part of bulkhead. I bought a precut one, it’s fairly complicated to cut to shape and I was putting it into a built up MPI with no room to work in there. Rover did fit open cell foam that I think was about 10 mm and always went very tatty and held water a bit, one of the first things I dumped.
3. Inside bulkhead we’ll covered with dynamat, probably doesn’t need any or much as it’s a pretty stiff panel anyway. Over the top, we have 15mm closed cell foam. Our old rover sound pads were knackered, they do have a good rubber mass loaded layer over crappy chopped open cell foam that holds water like the sponge it is. Had to chuck them out as were unrepairable. They’d be a good option for you, they do appear on eBay now and again.
4. Floor pan covered in dynamat. This was not needed as the rover panels stuck on are good enough. I had the mat left over from another job and thought it would tidy up the floor. We had went over the floor pan inside and out with a fine tooth comb and tidied it up. Sticking dynamat over a bad floor would obviously disguise any bad rust moth until it was too late. The inside floor got a few layers of POR 15. Over the top we have a full underlay of 10mm closed cell foam.
5. Our carpet is a Newton moulded one with a thin layer of foam on it anyway and that went over too.
The doors are lined with dynamat when the new skins went on, probably too much but it makes a serious difference, tapping the door sounds like your tapping thick steel.
6. Boot was similarly treated like the floor pan. We put some dynamat on the fuel tank and in the rear quarter panels and used a mix of the thick and thin foam. Our exhaust is a twin pipe DTM and can generate some serious drone / drumming.

I had put the new roof liner in when she was painted so it’s just the standard rover bitumen pads and thinning fibre mat. It’s an MPI liner so has an extra wee bit of foam on it.

Results are great, wish I’d used a sound meter at the different stages though.

What I’d do different -
1. Went overboard on the dynamat, I would use less and target where it went more efficiently.
2. It would be better thought out as a complete project rather during a rebuild rather than the piecemeal staged way we did it.
3. The Rover air ducting is foam lined, mine was stinking, lots of dead flies and dirt stuck in it and we binned the liner, I would have made more effort to clean it up inside the ducting and lived with it. I think I’ve a good bit of bay / road noise coming up the vent pipes.

At the end of the day it’s a classic mini, your never going to get great or modern car results to noise and some drivetrain / exhaust noise adds to the experience. Our exhaust is LOUD and puts out some energy, scares pedestrians at crossings and I can set the alarm off in my wife’s Bini and that’s great fun.

It’s a late MPI with a high final drive and that helps the noise when cruising. What we’ve got is what we were after, as refined a road trip Mini as we could have that fits in well with us. She’s not perfect or a show queen but I have good craic tinkering. We love her and I’ve a few people looking added to my will in case I should meet with a wee accident!!

[Alice Dooper]

A few wee working project pictures

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[IronmanG]

So what's the silver stuff in the pictures. Is this all available from the dynamat website?

[pete l]

https://www.ebay.co....y0AAOSw8AhaTJYj

[stoneface]

I used Noisekiller Lead Sandwich

Reduced the noise of the straight cut drops to bearable.

[Richie83]

All good advice. What sort of filter are you running? I ditched my K&N as it was noisy.