Talk Morgan Forums Community The Malvern Arms How loud is your MOG

How loud is the standard MMC silencer for the plus 4 ? Most modern cars now put out around 74 db the legal limit is 82 db, my plus 4 was tested tonight and recorded at 93 db at half throttle. Now I know that some small volume manufacturers and kit cars are allowed " more noise " but at 93 db does my car have the standard exhaust ?

My Plus Four howls under accelleration but had a deep burble when pottering. It is an interesting thought.

Most silencers get louder with age,as the baffles soot up with carbon.

The existing EU Noise test is flawed: this is what happens:

The current noise test for passenger cars, as set out in EU Directive 92/97 as amended, consists of driving the vehicle into the test area at a speed of 50 km/hr and then accelerating at full throttle through it past a microphone. The microphone is placed at a set distance from the line of travel and it measures the maximum level of noise reached which is then compared to the limit value to determine whether the vehicle passes or fails.

The test area is surrounded by an open area to avoid sound reflections and the road surface is carefully constructed to a set standard to ensure consistency of results.

No performance car is going to make much noise if full throttle is applied at 30mh in top gear. Which is how Mogs, Jags and others can make so much noise at high revs.

There is a new test on the way that shouldn't cause anyone any real problems: this is a good summary.

Noise

As tiime goes by we will probably see more use of "sport" modes, so that the car is quiet in normal mode and intresting in sport mode, with the use of sport mode prohibited in urban areas.

I suspect all 4 wheel Mogs are already compliant with the next round: the Plus 8 is very quiet, quieter than the Roadster, at all normal speeds: it is only when the revs get above about 4000 does the howl start...and then it just gets better and better...!!

It would be very easy to tune an exhaust to pass that test.
As all Morgan owners know there are certain revs that boom through the exhaust.
On my last 4/4 1600 the engine had a 1/2 race cam and with the 40DCOE's it sounded as if it was constantly doing hillclimbs.
When I changed to a Kent HI-Torque cam the difference in sound was remarkable. Timing of the camshaft makes a huge difference.

My 1200 GS bike already has ex factory an electrically operated valve in the exhaust to make more noise as the revs pass a certain point. Irritating TBH - makes it too noisy.

I believe that many exotica have similar systems.

Wonder what will happen with electric vehicles. I did the Lotus 60th celebration in 2008 and one of the cars on show was an Elise built out of reclameable materials ( jute I think) and electric powered. To get round the problem os the silence they had coupled a sound system and amplifier up to the throttle so it made exactly the saem noise as if it had a petrol engine.

Vehicle noiseis not measured at half throttle but under a rigidly defined set of rules. If you want to know more about it and the planned future regulations read this .

To get to the actual db figures you need to scroll down to Annex III

It all makes mind twisting reading

Ok , this may 'sound' radical , but how about having a sound test at a national meet or at local meets , the first 3 loudest get a prize , I'm sure there would be interest. Prizes could be funded by having a charity raffle and using a percentage of the funds . mad idea ? Or not .Would need to separate out the different engine sizes !

My next door neighbour who manufacturers exhaust systems tells me that that system is no longer legal on new models.

or how about this approach?