Exaust cut out valves... UK Legal?

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JUKE179r

Well-Known Member
Posts
3,166
Location
Suffolkshire
Is it legal to have exhaust cut outs? Will a car/truck fail an MOT if it has an exhaust cut outs?
I'm asking for a friend with a Disco 2 who wants more growl out of his V8. :D
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My Quattroporte which I had up to 3 years ago had the option to change the exhaust sound to a loud growl simply by touching a button on the dash screen, my brother owns an M4 that changes the exhaust sound when in sport mode, which sounds like the crackle and splutter of an F1 engine. So yes it is legal, no it doesn’t fail the MOT as it isn’t part of the test.

Fitting an open exhaust was done back in the days of carburettors mechanically, but it was found the vehicle didn’t run very well because of a lean mixture as a result, no problem with EFI of course. That system didn’t last very long after tail pipes came along which changed the exhaust tone, something the go faster hot hatch back soon had fitted.
 
should be,and any wanting to deafen the public banned from driving till they grow up
Yes, I agree totally. There is a little schit around here riding a moped scoot thing with no exhaust. I want to smack him in the face with a shovel as he goes past. It's only a matter of time till I get the chance to put him out of my misery.

Col
 
My Quattroporte which I had up to 3 years ago had the option to change the exhaust sound to a loud growl simply by touching a button on the dash screen, my brother owns an M4 that changes the exhaust sound when in sport mode, which sounds like the crackle and splutter of an F1 engine. So yes it is legal, no it doesn’t fail the MOT as it isn’t part of the test.

Fitting an open exhaust was done back in the days of carburettors mechanically, but it was found the vehicle didn’t run very well because of a lean mixture as a result, no problem with EFI of course. That system didn’t last very long after tail pipes came along which changed the exhaust tone, something the go faster hot hatch back soon had fitted.
Many 'new' cars - especially BMW's for some reason - actually play an exhaust sound through the car's stereo system so you get the feeling you're in an F1 Car (although BMW F1 cars were not that great)
https://www.cnet.com/roadshow/news/bmw-m5-generates-fake-engine-noise-using-stereo/
 
The crappy thing this lad rides must have the smallest engine imaginable, it's revving it's nads off and only doing about 20mph and it seems to take ages to get up to that speed.

Col
 
there is a legal noise level of 82 decibels for exhausts

Whilst bowing to your superior knowledge James I thought the decibel level was another 'in the opinion of the tester' scenario.
I agree it's a bit of a juvenile plan though, I've been known to drill small holes in the exhaust decades ago, but now I'm all grown up :rolleyes::rolleyes:
 
Whilst bowing to your superior knowledge James I thought the decibel level was another 'in the opinion of the tester' scenario.
I agree it's a bit of a juvenile plan though, I've been known to drill small holes in the exhaust decades ago, but now I'm all grown up :rolleyes::rolleyes:
i was thinking of the police, though they dont seem to bother too much with the idiots that drive round and round louth town center in raised discos with exhausts screaming, do they think any are impressed
 
I'm sure I've read that an MOT tester can fail the vehicle, if the exhaust system has been modified to increase noise output. Which would make an open pipe like the OP showed a MOT fail.
 
No mention of decibel level in the rools. Just subjective.
 

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I'm sure I've read that an MOT tester can fail the vehicle, if the exhaust system has been modified to increase noise output. Which would make an open pipe like the OP showed a MOT fail.
Possibly your referring to this quote from the mot testers manual: “Exhaust noise from the vehicle must not be unreasonably above the noise level you'd expect from a similar vehicle with a standard silencer in average condition.
If not... i’m happy to be corrected with the quote about ‘exhaust modification and increased noise that you read.

I’m sure if this vehicle was presented for an MOT or similar test the exhaust valve would be closed therefore exhaust would be flowing through muffler/s, which would be the case on any road/track competition vehicle subject to an MOT.
 
From what I remeber.(long time ago)
An MOT tester can (as has been said) fail a car on noise if he feels it excessive. I have not seen and not heard of any MOT test station setup with a sound meter. Maybe it is the case now.
And on the level, my IVA docs state 99db (may not be the most up to date)

As for altering an exhaust like that, a tester might just fail it under “alteration to emissions system “or something similar, weather it does or doesn’t .

So don’t advise it, it’s stupid young kid stuff.:oops:

But at the end of the day why???? All my V8s when I wind down the window and give it some welly sound fine to me:):)

J
 
The MOT man at the garage I work at will fail a car above a certain level, 84db limit I believe.

He is usually less lenient around knob ends in corsas with a straight pipe.

So they do use db meters then:D I can just imagine what the boss would say if the all garage work stopped so the MOT tester could get an accurate meter reading.

If he found my vehicles to loud, the first thing I would say is your meter calibrated like mine. I had to buy six but we only had 5 engineers at the time, so I kept one, and used when I stepped in with commissioning of a fire alarm system... no engineers spare to do the job.:(

Out of interest I’ll be checking the exhaust dB on my cars next weekend. Sound system in the disco peaks at 91db without distortion.
 

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