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Hot!Exhaust noise - cabin vent

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salem
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2017/12/29 11:44:51 (permalink)
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Exhaust noise - cabin vent

I finally got my old money pit back on the road (1994 SW20 - now with a Celica GT4 3S-GTE engine swap of unknown origin or vintage - I am sure I'll be back with plenty more issues), and I am not used to the exhaust drone any more (been years off the road).
 
The little cabin vent behind the driver right shoulder looks to be where the peak of the noise is coming in (my 3" exhaust exist on that same right hand side). Is it possible to dampen that little vent or block it up without suffocating? I'm assuming there's a ton of air leakage elsewhere anyway. I couldn't see a way to remove it from the outside, and on the inside it's just some holes in the internal b-pillage moulding, not a piece to remove.

Black 1994 SW20 turbo coupe - with GT4 3S-GTE engine swap
#1


16 Replies Related Threads

    Reddtarga
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    Re: Exhaust noise - cabin vent 2017/12/30 20:15:54 (permalink)
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    Are you sure the sound is coming from that vent? In the small MR2 cabin sometimes it can be hard to tell. 
    I've been told it is tricky removing it and it's easy to break the clips when trying to get it off.
    Maybe try tape over the outside just to block it to see if it makes any difference before you bother.

    1990 ADM NA
     
     
     
     
     
    #2
    salem
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    Re: Exhaust noise - cabin vent 2017/12/30 20:21:33 (permalink)
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    Yeah I guess I'm just assuming. I'll pop a temporary makeshift muffle patch over it and see how I go.

    Black 1994 SW20 turbo coupe - with GT4 3S-GTE engine swap
    #3

    Admin
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    Re: 2017/12/31 09:23:30 (permalink)
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    There may be a hole in the firewall I.e. A missing rubber bung.

    #4
    salem
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    Re: 2017/12/31 09:52:23 (permalink)
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    Is that something I can find myself, or does the engine need to come out ? (Please god no)

    Black 1994 SW20 turbo coupe - with GT4 3S-GTE engine swap
    #5
    Admin
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    Re: 2017/12/31 10:03:20 (permalink)
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    Get a length of garden hose, stick one end in your ear, the poke the other end around inside the cabin behind the seat while the engine is running. If there is a leak, you will be able to hear where it is through the hose.
    #6
    salem
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    Re: 2017/12/31 10:24:08 (permalink)
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    You have a hidden camera set up near my car to record the hilarious nature of this test, don't you? But cheers for the tip

    Black 1994 SW20 turbo coupe - with GT4 3S-GTE engine swap
    #7
    Reddtarga
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    Re: 2017/12/31 10:57:01 (permalink)
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    You could make the garden hose more sensitive if you tape a small plastic funnel to the end of it.
    Great for tracking down other noises as well.
    Or even better, ask your doctor to lend you a stethoscope. 

    1990 ADM NA
     
     
     
     
     
    #8
    TwoDogs
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    Re: 2018/01/19 11:51:00 (permalink)
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    Done the funnel in the hose trick, works brilliantly for finding hissing leaks around an engine and no reason why
    it won't work in this case. Quite precise.
    I am in the middle of soundproofing my Sdub and behind the panel behind the driver's shoulder, is a hole for the seat belt mounting and a hole for the rear crap speaker (removed). That cavity brings a ton of fan and rear tyre noise into the cabin. The same cavity on the other side also, but no fan. If there is one place to fix, that is it. I have lined the cavity with stick on vinyl and filled the cavity (mind a couple of cables) with high density foam. All up 2hrs and $40 (at a guess.) I need to complete some other tasks before driving to confirm the result. 
    #9
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    Re: 2018/01/28 11:06:30 (permalink)
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    Did it work?

    #10
    salem
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    Re: 2018/01/28 17:41:31 (permalink)
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    Sadly I've been too busy to have a crack at it yet. And/or when I do have spare time it's way too bloody hot to be mucking about with the car. I have a few weeks off work now though so I should be able to get in there in a few days or so.

    Black 1994 SW20 turbo coupe - with GT4 3S-GTE engine swap
    #11
    salem
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    Re: 2018/04/20 16:59:01 (permalink)
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    So I didn't find any obvious noise entry points. Droning is also audible out the left hand passenger side (as reported by aggravated girlfriend) so I suspect my exhaust is just a noisy sod. Might get the mechanic to check for exhaust leaks/mounting issues. The exhaust does also have an annoying rattle at just the right speed/revs.

    Black 1994 SW20 turbo coupe - with GT4 3S-GTE engine swap
    #12
    TonyMR2
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    Re: 2018/04/20 19:50:17 (permalink)
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    Check the exhaust over for any leaks.  Second option - electric exhaust valve motor.  They are throttle body like valves, that can be installed towards the end of your exhaust system and hooked into the vehicle wiring (depending on ecu or aftermarket switch maybe required).  At low throttle the valve sits partially open, reducing airflow and sound, at open throttle they open for full flow.  ATS Racing facebook page had a post a while back.
    #13
    TwoDogs
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    Re: 2018/05/02 18:07:54 (permalink)
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    I think you're right Salem, despite my efforts the droning continues. Certainlky road noise is down but it pales in significance. I suspect even the poly rear window may transmit some of the droning.
    Just as woofer noise goes out the body shell, I suspect low freq exhaust noise to bounce off the road into the cabin.
      
    #14
    TwoDogs
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    Re: 2018/06/13 16:06:28 (permalink)
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    More on the engine drone. I was sitting at the lights the other day and a big thumper pulled up next to me.
    Either a Harley or a Trumpy or something. With my windows closed I could hear and feel the bike idling and it
    was all coming through the floor. So although I have put some vinyl sheets on the floor, it is not enough. Thinking about pouring fiberglass resin on the floors to increase the weight....might try one side first. Bonus would be that my subw would cause less doof, doof for my fellow roadusers. There will undoubtedly still some engine drone in the cockpit but any reduction makes the music nicer.
    #15
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