Posted 03 February 2020 - 01:16 PM
I honestly can't put my finger on what to try next. I have applied silentcoat to every panel barring the roof, thick carpets and matts, still with no success.
It's making long journeys horrible. I do find if I press on past 4000rpm the droning goes away.
Posted 03 February 2020 - 01:24 PM
Any defective rubber mounts? Is the pipe touching the body at any point? Tap the silencers with a rubber mallet to check if there’s a loose baffle in there?
Posted 03 February 2020 - 01:29 PM
I can only explain the sound as like 'sitting inside a drum' the whole cabin literally fills with this awful drone.
Posted 03 February 2020 - 05:10 PM
Swapped to mild steel and was much easier on the ears.
Posted 03 February 2020 - 06:06 PM
I found with Cams over 285 degrees, moving the 2 silencers further apart helped a lot but I found it did only hit a resonance at around the 3200 rpm mark, under and over this, wasn't an issue. It might take a few stabs at it. I just tried moving them apart first and that worked in this case. For you, they might be happier coming closer together.
Posted 03 February 2020 - 06:34 PM
I have MLV down the exhaust tunnel and the bulkhead and closed cell on top of that. Makes a massive difference inside. Still loud at top cruising speed but you can still talk to passengers
Posted 03 February 2020 - 08:18 PM
I cured mine (as much as you can in a classic mini!) by fitting the under bonnet sound deadening kit from minispares. Admittedly it hasn't made a huge difference to the overall racket, but it did cure the booming at 4000 rpm.
My theory here was that my bonnet had a resonant frequency that was at its highest with the engine running at 4000 rpm and the sound deadening kit just moved the resonant frequency to somewhere else!
I'm not saying this is definitely your issue but it cured my issue.
Posted 03 February 2020 - 08:27 PM
Fix it with a dab of contact adhesive here and their.
Then on top of that a layer of 8mm closed cell foil backed self adhesive sound proofing on top. Seal all the joints with a roll of aluminium tape. Get something on the underside of the bonnet.Put it all back together and you would not believe how quiet the cabin will be.
Edited by Chris1275gt, 03 February 2020 - 08:29 PM.
Posted 03 February 2020 - 08:55 PM
You'll be sticking with your 1330 no doubt so change the exhaust to mild steel, also consider an mg metro cast manifold in place of a tubular setup
Edited by ads7, 03 February 2020 - 08:56 PM.
Posted 03 February 2020 - 09:54 PM
Is there really much of a difference in a mild steel twin box setup over a stainless twin?
Posted 04 February 2020 - 06:01 PM
Posted 04 February 2020 - 06:30 PM
I've a 1310cc, Kent cam etc so similar power to yours.
I switched to mild steel rc40 but with a large bore box and found it a lot more friendly to drive!
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