The new MOT regulations are now extended to noise levels (considered a nuisance), So the rules state that any exhaust sound level shall be monitored during an MOT test, with conformance required as being equal to a standard OEM noise level when the car is new. This seems to be a secret, as the tester is instructed to consult statistics retaliative to the car you own, type, and normal sound level. ( I have no idea in decibels what this is).The tester is told to run the engine at either 2,000 rpm (if no maximum rpm is known) OR - to half rpm level where it is. As most Mx5' will run up to 7,000+ rpm, then the sound level will be checked at a minimum of 3,500 rpm.
(Post interrupted by Windows Defender, so had to log off, and log back in)
Along with many owners, I bought a S/S single exit back box (silencer) from MX Parts back at the 2010 Rally at Chatsworth, a Bargain I thought at the time. Same exhaust box is still on MX parts, but now £199+ (I paid about £105 back then) However, I was a bit worried, as in previous years several owners had commented that most of the silencing material had 'gone with the wind' so being cautious, I kept the OEM back box. Since Christmas last, the sound level has gone up to what I would term 'an embarrassing level' and I called in at my MOT garage and asked for their pinion. "Iffy" was the comment when they ran it up to speed. I said I still had the old back box, but when I checked the shed it was stored in later, I realised my son must have dumped it - long story.
In desperation I asked the area if anyone had a Mk 2.5 back box they didn't want - no reply. Rang PM Sportscars at Shardlow, and they said "We've got at least a dozen here", so bought a fairly good one for £40. This place is now an Aladdin's cave, chock full of rescued parts, so well worth remembering. (PM me for address etc)
So - with spare box in the boot, took the car for sn MOT, with a promised from the owner that if the S/S box was a 'no pass' for sound levels, he would fit the OEM box instead - at no charge. Failed on the S/S box, so now driving on an OEM one.
Now - I'm not in the practice of knocking MX Parts for selling rubbish, but that same box now carries a five year guarantee, which is about the time it was on my car, having been fitted in 2011. New - sound was what I wanted, changed from a chuff chuff to a nice rumble, but this year that turned into a lions roar instead.
So - be careful which exhaust you buy - or bought, you may love the sound, but will it stand the MOT test?
What doesn't help, with the Mk 2.5 with VVT - VVT kicks in at 3500 rpm, and the 'half max' sound level is 3600 rpm.
Edited by user 10 October 2018 17:24:32(UTC)
| Reason: Post interrupted.