Muffler noise and MOT

Dyno Soar · Post by **Dyno Soar** » Wed Jun 01, 2005 5:58 pm

Is there a niose limit on cars for the MOT test? I am going to be running a temporary streight through silencer insted of my back box and its gonna be a bit niosey.

Will it fail the MOT?

Nige · Post by **Nige** » Wed Jun 01, 2005 6:54 pm

Yes they do test the noise level, how and to what extent I'm unsure. Might just be a discretional thing left upto the MOT tester?

roger · Post by **roger** » Wed Jun 01, 2005 6:55 pm

No there isn't a noise limit. As long as you have a silencer and the exhaust isn't blowing you will be fine.

stevieboy · Post by **stevieboy** » Wed Jun 01, 2005 7:09 pm

Alam, i,d be very suprised if there is not a noise level. There are on bikes and its 88 decibels. I have to put my standard exhausts on every time (as the,re 110 decibels) I go for an MOT.
I,d check.

what time you usually home ?????

shambly · Post by **shambly** » Wed Jun 01, 2005 7:32 pm

I think that there is a date of manufacture from when a noise limit applies and that my 72 is not subject to it as i've had the same concern.

Lightweight_911 · Post by **Lightweight_911** » Wed Jun 01, 2005 8:44 pm

I think the answer is a combination of some of the previous replies:

there is a noise limit but it's not quantified - it's discretionary & open to interpretation by the particular examiner.

From the VOSPA (Vehicle & Operator Services Agency) website:

Under items to be inspected:

Exhaust System
Complete, secure, without serious leaks and silences effectively.

& under reasons for failure:

The exhaust system will fail the MOT if:

· Part of the system missing or excessively deteriorated
· A mounting is missing or damaged so it does not support the system
· There is a major leak
· The system is excessively noisy.

Dyno Soar · Post by **Dyno Soar** » Wed Jun 01, 2005 11:14 pm

Ahh bulls...

Well the car is niosey but only a little more then some 911's that I have seen with streight pipes. Perhaps I could give it a try and see what happens..

If that fails I could go for a proper smaller rear box that runs through straight. Perhaps I'll try deemon tweeks.

Steve I get home for around 7pm. If you could give us a hand figuring the washer system would help.

Thanks again guys.

PAUL CALDERBANK · Post by **PAUL CALDERBANK** » Thu Jun 02, 2005 2:12 pm

I seem to remember someone on the early S registry saying that you can quieten an exhaust by putting stainless steel wool in it! Not sure how much it would need and whether you'd get away with just putting some in the pipe or how it would run etc (don't want to pack it in too tight!)

PAUL CALDERBANK · Post by **PAUL CALDERBANK** » Thu Jun 02, 2005 2:16 pm

Just so that you don't think I'm pulling your leg, here's the link (I also posted this one for Barry's pre74 sports exhaust thread).http://d240157.u39.zeonhost.com/forum/s ... php?t=6292

PAUL CALDERBANK · Post by **PAUL CALDERBANK** » Thu Jun 02, 2005 2:23 pm

Hmmm duff link eh! Lets try that again.

http://d240157.u39.zeonhost.com/forum/s ... php?t=6292

Have a look at "Cosleys" post on that thread. If this link still doesn't work the go to barrys sports exhaust thread in the 911 section, it's in there.

Nige · Post by **Nige** » Thu Jun 02, 2005 2:30 pm

SS wire wool is used as sound deadening within the muffler, along with other materials and products. Though you're going to have to cut open the muffler to do this.

roger · Post by **roger** » Thu Jun 02, 2005 5:30 pm

Another possibly simpler way of cutting down noise is to fit some aluminium sleeves into the tailpipe(s), held in with grub screws. This reduces the bore of the pipe and quietens it down. I have a friend with a Cobra and he does this for track days.

Dyno Soar · Post by **Dyno Soar** » Thu Jun 02, 2005 9:03 pm

Roger do you have pic of the said modification?

Perhaps that maybe the simplest answer.

roger · Post by **roger** » Thu Jun 02, 2005 9:26 pm

I'll send you a PM shortly with a diagram in Excel - hope you can read that.

Dyno Soar · Post by **Dyno Soar** » Sun Jun 05, 2005 10:55 pm

Thanks for that Roger...

I am now considering a supertrapp for the end and removing it after the test. They may find it tricky to check my emissions though.

Stupid thing is the oxygen sensor is not connected so it must be running rich... I must investigate?!?!?!?

what do you guys think?