The road and decibel test was conducted on a track void of traffic noise. The object was to compare interior noise between the soft top and PRHT, the latter of which had been recently introduced. I only use the detachable hard top during the winter months and although I can’t say the car’s noisy with the soft top, it’s a heck of a lot quieter in traffic and there’s less wind noise with the hard top.
When we first got our MX I actually investigated having noise insulation fitted, and found that it ranged between £500 to £900, depending on what type and how far you wished to insulate.
As it is now the car’s quiet enough that I don’t need to consider this additional cost, however Denbow I’ve just seen your exhaust spec and I’m surprised you can hear anything!
Ahh, the exhaust system and noise insulation…well as you come to mention it.
Insulation - Last summer I insulated the entire boot floor, sides, the back of the plastic panel and floor behind the seats with 10mm self adhesive closed cell foam. This makes a huge difference with less drumming from the boot and reduced road, tyre and exhaust noise.
Exhaust - I’d already fitted a Cobalt rear box and as the mid section appeared crusty I recently replaced it with a stainless steel one from Japspeed (off Ebay). These do away with the 2nd cat and resonator box and has a small sports cat in place of the latter. However, this wasn’t without problems making it clear the IL Motorsport chassis bracing set. The exhaust sound was tremendous, much too loud for everyday use and I began to regret the change. Then I struck on the idea of fitting a motorbike ‘decibel killer’ in each tail pipe. These work a treat, the car can now be driven around quietly when required, has a deep burble on tickover and a lovely rorty growl accelerating through 2500 - 2750 rpm. The only thing I’m not 100% happy with is the low speed popping on the over run which some people love. It isn’t intrusive and virtually inaudible with the soft top up so I may leave things as they are for the time being.
Oddly enough, I never considered that the MX-5 was particularly noisy - especially comparing my memories of things like MGBs, Spitfires and Midgets from when I was a mechanic in the 1970s. Adding extra sound insulation to my 5 never crossed my mind.
I suppose after my wife had had two delightfully quiet Mazda 6 company cars, before she got our first 5 back in 2011, the roadster did have more general ‘road noise’ about it, but we just put that down to the type of car that it was, and lived with it - without any great hardship it must be said. It was kind-of expected really I suppose, and our first drives in it gave us the impression that it was a very civilised sports car (sorry, roadster).
In fact, I was rather wishing that the 5 had more of a burbly exhaust note, and am seriously considering something like a Cobalt rear end should the present fitment ever fail the MoT in the future. I read Denbow’s experience with noisy exhausts with interest, and have made a mental note not to go down the road of the de-catted centre section - too much of a ‘good’ thing perhaps !
Chris, you won’t go far wrong with a Cobalt exhaust. Mine’s been on for 7 months and has developed a really nice low growl and a burble on the overrun. The burble alone is enough to make me keep going through the gears on twisty roads! The exhaust is not intrusive at speed, roof up or down. Compared to other big exhaust systems on the market, I’d say it’s the best value for money by a country mile.