Exhaust noise: ears are ringing, worried I'll go deaf

[johnsimister]

My Shorrock-supercharged '59 sounds great but two half-laps of the M25 yesterday, to and from a very fruitful rolling road session with CCK, have had me wondering if I'll ever hear properly again. There is plenty of bulkhead soundproofing on both sides, the speedo aperture is full of felt and there is felt under the carpet. I'll probably add more to the rear bulkhead, shelf and seat pan, and also to the underside of the bonnet. But I feel it needs more than that - it's the all-pervading low frequencies that are the problem. At one point my ears were actually aching.

Some of it is induction roar, but I think most comes through the structure from the exhaust. It's a two-box RC40, not all that loud from the outside. Its rear end hangs on the usual rubber block and two bobbins, which seem quite stiff.

My question is: would the later mounting system, hanging from rubber loops like a modern car's, be significantly quieter? If it would, I can get the later tail silencer and the Minispares conversion for the forward mounting that bolts to the subframe, but is there an obvious way of re-creating the rearmost mounting (the two-bobbin one) to use the rubber loop?

We've entered the MCR's Minis to Ireland in September, and I really need to make my car quieter for that. Otherwise my wife might never talk to me again, and even if she did I wouldn't be able to hear her.

John

[Chris64]

I know what you mean John, I run a single box RC40 but I dunno, I'm not sure I would have said the exhaust noise was the predominant racket compared with the gearbox, road noise, induction roar etc. I'm always in two minds though, apart from on a long or motorway journey, I quite like it being noisy

I resort to these on the motorway:





A while ago someone mentioned putting a thin foam roll into the fresh air hose as that brings in quite a lot of noise from the engine bay - you can actually hear the difference by putting your hand over the heater end even when the car is idling and stationary. I haven't got round to trying that yet though.

I'm interested to hear the replies too.

[johnsimister]

Earplugs... yes, the pragmatic solution! There's a pair sitting in the driver's door pocket but they're a bit of a conversation killer. I was wondering about some sort of intercom system but I can't help thinking there's a better way.

No fresh air duct in my car, being so ancient. It would be even worse if it had one.

I agree about the joys of noise. I've just been for an illicit blat around the lanes in mine, when I should have been working, and it is brilliant fun. Now my ears are ringing again. I was trying to discover whether the loudest source of the noise was towards the front or the back, and it does seem to be more rearwards. But that could just be standing waves of resonance in the cabin.

John

[rich@minispares.com]

john

c-ara670

c-ara671

you could weld some bars onto your original rc40 to use the rubber pigs noses, or buy the version that has them prefitted - but this would be a rear silencer and a separate down pipe with silencer.

[johnsimister]

Thanks very much, Rich. Looks like those brackets could be the way to go - but do you think the pig's nose rubbers would insulate the car's structure from the exhaust noise any better than the existing mounting system?

Hoping it's a yes...

John

[rich@minispares.com]

Thanks very much, Rich. Looks like those brackets could be the way to go - but do you think the pig's nose rubbers would insulate the car's structure from the exhaust noise any better than the existing mounting system?

Hoping it's a yes...

John

john

they really work well

[In the shed]

Don't take any risks with your hearing.

I have been wearing plugs in my minis since about 2003

[IAIN]

I had a problem with noise in my 82 mini pick up which was very similar to what you describe. It has a standard mini 998 engine, but when driven at about 50, 55 mph it would start to get uncomfortable to be in, the noise seemed to drum in the cab at that speed. I've never had this problem before. It might be a problem in pick ups ?.
The prevous owner must have felt the same, because he had put sound proofing in every possible corner in the engine bay and dash area.

I recently decided to upgrade and improve the exhaust, I fitted a standard injection cast manifold, twin injection down pipe to a link pipe then a standard injection twin back box ( on hangers ) and that solved the problem.

I had to shorten the height of the twin down pipes to fit the 998 properly, my point here is that the twin down pipe exhaust has two tubes one inside the other, which I think is the biggest reason it is much quieter now , and it dosen't drum inside at 55 mph.

[pad4]

Ahh youre just getting old, next will be comfy seats

inside my 8 port, one day i used a sound meter (iphone app) it went right of the scales at 130 Db
and at certain speeds there must be a resonance that you can only feel in your mid chest which makes you feel sick

Joy



Pad

[Andrew1967]

I had a problem with noise in my 82 mini pick up which was very similar to what you describe. It has a standard mini 998 engine, but when driven at about 50, 55 mph it would start to get uncomfortable to be in, the noise seemed to drum in the cab at that speed. I've never had this problem before. It might be a problem in pick ups ?.
The prevous owner must have felt the same, because he had put sound proofing in every possible corner in the engine bay and dash area.

I recently decided to upgrade and improve the exhaust, I fitted a standard injection cast manifold, twin injection down pipe to a link pipe then a standard injection twin back box ( on hangers ) and that solved the problem.

I had to shorten the height of the twin down pipes to fit the 998 properly, my point here is that the twin down pipe exhaust has two tubes one inside the other, which I think is the biggest reason it is much quieter now , and it dosen't drum inside at 55 mph.

Interesting read Iain.

I had exactly the same problem with a 1980 850 pick up I recently restored (standard spec). It was fine up to 50 but then from 55-60 it would drum quite badly. Over 60 and it tailed off and went quiet (for a Mini) again. Typical that it's 55-60 that an 850 seems happiest at ! Now in Japan, so I'm not too worried about it on this particular pick up!!

I have a 1975 998 pick up to finish off at some point. I am keeping this one so its interesting to read of a possible cure for the problem, should it arise.

[rich@minispares.com]

my point here is that the twin down pipe exhaust has two tubes one inside the other, which I think is the biggest reason it is much quieter now , .

rover discovered this trick in the 1990's and a lot of their cars had the double tubed down pipes. they make a huge difference, my old metro 1100s had them and when I fitted an aftermarket set of single tube down pipes it didn't half make a noticeable difference to the noise

[thefarmer]

I have a similar issue with DKG2C in the sense of the car being too loud for driving over lengthy periods. Different cause though...its down to the weber staring at me (albeit with a speedo in between) and the s/c gears. Measuring the noisy levels, its pumping out 108db at 4000 revs and with a final drive of 3.76 you are going to hit that quite a bit on A roads etc...obviously those with 3.9 and beyond will suffer even more. I didn't want to change anything though...the car was built that way, so i wanted to keep it that way. I spoke to the previous owner Peter Barker who rallied it alot and he was wanting to go down the intercom route....however Willy Cave was against any such wizardry and so they suffered. According to Peter he is now partially deaf in his left ear. When i picked the car up and drove it back up to Scotland from Cambridge, both of us had nearly lost our voices by the time we got back.

I have gone down the intercom route, but its a bit more subtle than the usual set of 'cans' you would have on your head. I have put a starcom system in there which is basically a motorbike setup. It has a number of options regarding earphones, mikes etc depending on whether you want to have a helmet or not. The net effect though is that it takes a lot of the sound out, you can speak easily with your passenger (if he/she is also plugged in) and you can still hear what the car is doing. If you want, you can plug all your gadgets into it as well to listen too.



I'm also going to Minis to Ireland and it was one of the reasons for installing it. No drilling either...lovely velcro everywhere!!!!!

PM me if you want any more info. My solution is purely based on not having or wanting to change anything on the car and also avoiding giving the impression that i'm a wannabe rally driver!!! That's going to have to wait until next year....

BEN

[johnsimister]

Thanks for all the replies. The intercom sounds the perfect solution but meanwhile I have ordered sufficient parts to create a two-box RC40 exhaust with rubber-loop hangers. With that and some more soundproofing I hope it will be OK. It has a 3.4 diff which would make it a reasonable cruiser were it not for the fact that the racket is at its worst at motorway speeds. It would be quieter if I did 90mph everywhere, but unfortunately there are snags to that approach.

Ears still singing, three days on... but not as much as they were.

John

[rich@minispares.com]

. It would be quieter if I did 90mph everywhere,

I don't think even nick freeman would be able to do anything with that defence!

[johnsimister]

Would it help that my speedometer seems to under-read? No, thought not...