Loud exhausts and passing the MoT

Discussion in 'Cars, Bikes 'n AFVs' started by REMEbrat, Jan 12, 2008.

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  1. How is it cars fitted with loud exhausts are able to pass the MoT test?

    The garage has to check the exaust system is 'complete, secure, without serious leaks and silences effectively'. I thought the whole point of a loud exaust was that it doesn't silence the enging effectively.

    I also know there is a miximum noise limit for engines set at, I believe, 55 decibels. Is this checked at all?
  2. About 5 years ago (back when i was at school) I did work experience at a car workshop doing MOT's, Services etc. Not on my own I hasten to add. Back then we didn't check the noise just the emissions from the car. That may only be with that workshop though.
  3. The maximum noise limit is higher than 55 decibels. A hairdryer is probably more than 55 decibels. I know that the exhausts on my bike are 87 decibels at idle and they are nowhere near the maximum. I also know that for a noise check on the MOT they don't rev the engine, it is done at idle.

    I know one person who's bike is only about 1 decibel below the maximum limit when his bike is idling, so it passes the MOT.
  4. You are assuming that these chavmobiles with the loud exhaust have actually gone through an MOT test.
  5. My MOT tester fails any chavmobile that comes in with blue neon lights
  6. The dft site gives advice for importing cars to the UK (my bold):

    NOISE: Engine/Exhaust noise must not exceed 101 decibels at the approved measuring point. Not expected to require any modification except possibly for faulty/worn or some ‘after market’ systems.

  7. Alsacien

    Alsacien LE Moderator

    I thought the db was measured 2mtrs in front and 1mtr to the opposite side of the pipe at 5000rpm?

    87db at idle is loud - my 54mm open system on the Ducati is rated at 105, but is almost silent at tickover - wakes the dead when it backfires off the limiter at 10,950 though... :twisted:
  8. I thought the noise limit was 98db? could be wrong, and polar, why would the tester fail them for the lights straightaway, they arent illegal?
  9. Yes they are!

    About half way down on link; http://www.ukemergency.co.uk/information/bluelightuse.htm
    "Only emergency vehicles can be fitted with a blue flashing light, or anything that looks like a blue flashing light, whether working or not."
  10. aha! i stand corrected, thankyou, i always thought that they could be fitted but not used or able to be seen when on the public road. not that my car has such things
  11. Not sure about cars, as my exhaust is very quiet, but on my bike I have an after market can.

    The last 2 MOT's haven't been a problem, even though, there is no kite mark or BS stamp on the exhaust. I was led to believe that it was up to the individual tester to decide whether the exhaust was too loud or not
  12. Mine are custom, hand-made exhausts. It's a 1985 Eliminator, can't get replacement exhausts when the collector box rusts through. They're 87db at idle, and 110db at only 7,000 rpm. Haven't measured them at the full 10,500 rpm that the redline starts at. :twisted:
  13. The correct RFR(reason for rejection) states: noise is clearly in excess of that emitted by a similar vehicle fitted with a standard silencer in a average condition.

    This is for cars and there is no requirement to check decibels so as you can see its down to the judgement of the tester,don't know about bikes and I ain't a spotter just a tester.
  14. I know for bikes that if the exhausts are BS marked then they are generally fine. If they don't have the BS stamp then it is up to the tester on the day.