Most of them have ridiculously noisy and large silencers (or rather not silenced) fitted - they seem to work on the principle that 'more noise = more speed' - I was told that these cars are tested with the original makers silencer fitted and once an MOT was acquired the noisy one was fitted instead - surely this is not legal? Just curious - any sensible answers out there?
2007-03-20 03:41:09 · 8 answers · asked by Anonymous in Cars & Transportation ➔ Safety
Its at the discretion of the police/mot tester wether or not its too loud. Under new laws in the UK the police can confiscate cars they deem too loud/nuisance
2007-03-20 04:20:06 · answer #1 · answered by Anonymous · 1⤊ 0⤋
To understand why the cars are so loud you have to have a basic understanding of how the "loud noise" actually helps. The loud noise of a "boy racer" is actually an aftermarket performance exhaust that has been installed. In all of today's production cars manufacturers install mufflers to muffle sound and also catalytic converters to convert harmful exhaust gases to more eco friendly gases that also muffle sound. The downside to the sound dampening devices is that they restrict the flow of the exhaust.
To get an idea of what this means, blow through a straw. Then bend or pinch the straw and try to blow through it. The increased pressure and blockup causes you to exert more force just to blow air through. The same gereral principal works with exhaust systems. When you free up an exhaust system with a straight through muffler and a high flow catalytic converter you are increasing the power output of the motor which makes the car faster. Even something as simple as a straight through muffler can have minimal gains.
The flip side is that freeing up the exhaust like that also allows for more sound to escape the motor. Since a motor is basically a series of controlled explosions it's bound to be quite loud.
So how do they get around noise restrictions when being tested? Some exhaust systems come with an outlet reducer that slides into the tailpipe. This reduces the outlet size from something like 3-4" to about 2" which also effectively blocks flow and reduces noise levels. After testing they simply remove the silencer to increase power and noise again.
One thing to remember is that this principle doesn't just apply to "boy racers" and Japanese cars but to ALL cars, even good ole' fashioned American muscle cars.
2007-03-20 03:57:32 · answer #2 · answered by Ryan 2 · 4⤊ 0⤋
Not sure about the rules and laws there. Here a modification from factory specifications of the muffler system is an offense that will bring a fix-it ticket at the least, and may get your vehicle impounded at the worst. I'm sure you have something similar there.
2007-03-20 03:48:40 · answer #3 · answered by oklatom 7 · 0⤊ 0⤋
For a car to fail on sound levels, it has to be extremely noisey.
Many of the loud boy racer cars you hear dont even compare to the noise produced by harleys or high perfomance sports cars
2007-03-20 03:48:26 · answer #4 · answered by Anonymous · 0⤊ 0⤋
Boy Racer Exhaust
2017-02-20 22:18:29 · answer #5 · answered by ? 3 · 0⤊ 0⤋
I lot of those are just bolt ons which are removed for the MOT then just put back on again.
2007-03-20 03:56:57 · answer #6 · answered by Dark_Mushroom 4 · 0⤊ 0⤋
The sad truth is, most of them don't actually have MOTs. Or tax. Or insurance...
2007-03-20 11:08:50 · answer #7 · answered by Nightworks 7 · 3⤊ 0⤋
they keep the original exhaust and refit it for M O T lucky we dont do the same with tyres
2007-03-21 01:02:05 · answer #8 · answered by Bernard H 1 · 0⤊ 0⤋