NC Exhaust systems

Hi, I recently bought a 2L 2010 NC sport roadster mx5. The car is my daily use/commute/leisure driving vehicle. The 160 bhp is enough for me at the moment but I wanted an exhaust to be a bit more throaty.

I don’t really want a race spec exhaust system as the car has to pass the mot but I was considering spending £1800 from Roddisons Motorsport for a full stainless steel system that would come with an inlet filter and an ecu remap. However when I rang him today he said due to shipping increases his prices have changed and I’m now looking at £2.6k for an complete exhaust system. BBR Super 185 is pretty much similar money for the same thing.

So my question is… are there any other cheaper options for a full a stainless steel exhaust system (that will pass an MOT) for less than 2k?

Various threads on search for this subject.

I think you are sort of asking several questions here?

  1. New complete sports exhaust?
  2. A 4-1 header?
  3. A different intake?
  4. A complete remap?

Just my experience.
At the time in 2018, there were 3 companies I narrowed down for all the above packages. Some didn’t do the full exhaust, a bit of “what do you really want”.
Skuzzle,(now gone the one I used) BBR and Rodders.
Others of course and depends where you live etc.

Rodders does use high quality parts (Racing Beat) and highly recommended.
BBR uses high quality parts of there own brand and again comes highly recommended.
The other proven header is the IL Motor Sport 4-1.

I don’t think you will find a quality upgrade (fitted) package that you want for sub £2000 nowadays.:man_shrugging: Remember you do get what you pay for. If you do well done and good luck. :+1:

Just an opinion treat yourself to an early Christmas present and put your hand in your pocket and go to Rodders.

You could go to Powerflow and ask them for a SS quote. But why go to that expense and not release the power that you would get from the packages? There are others out there in particular the Northern end of the country for SS upgrades. Google is your friend. Good luck. :slightly_smiling_face::+1:


thanks… well I have booked a slot with BBR for a complete exhaust system and a service.


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I had the Racing Beat system fitted back in 2015 and very pleased.


Well done and enjoy, its only money!
As a tip (from experience), just be “Careful” which back box/silencer you go for.
Just don’t go too loud.
They can sound great at the beginning, but far too loud and annoying as life goes on.


Yea im going for the GT end can.


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I have the 4-1 IL without cat and center section with sports cat, I pass our MOT (not UK). Stock backbox. Really happy with it actually; the sound is, even though not a Honda B-series or K-series (pretty much my reference for a 4 cylinder), a LOT better. It doesn’t sound like it’s whining anymore and there is some more noise but no droning whatsoever and I am not bothering the neighbours. When cruising I really have to listen carefully to hear any difference in sound quantity, also a plus of this setup. The power hike is already noticable without a remap, especially in higher RPM and throttle response has also already much improved. Most important: I enjoy the engine and therefor the car a lot more.

Can’t wait to get a remap, but I need some other things done on the car and also need to keep the wife happy in terms of bank account balance :wink: I do know I’d much rather get a 4-1 and center section with a remap than a full exhaust without remap. Backboxes are expensive on the NC because of the size and dual exit, while they are probably the least restrictive part of the stock exhaust and I believe they’re even from S/S. I would also much rather spend the money on suspension or brakes improvements than on the backbox.

Unfortunately any removal of a cat is an mot failure in the uk so we got to have them.

I could just buy a rear muffler and do it on the cheap but im keeping the car for indefinite so i don’t really mind spending a bit of money and do it properly. My car is a 6 speed sports roadster so i have good suspension (that still works just fine). I did think about the calipers and using braided hoses but im not really using the car on tracks so its not high on the list of things to do for me.

Next will probably be taking it to a body shop to check it for any rust underneath - possibly redo the underseal if its needed, then perhaps brakes. I don’t really think I’m going to change anything else in the engine as mine has 75k miles so… it has seen some miles and i don’t really want to blow it.

Not sure I would agree with that statement.
Yes, discussed to death before but…

Copy from my previous post.
For your information if you are thinking of modifying or indeed already have modified your exhaust system. In particular the NC.

This topic of people saying it’s an instant MOT failure if you remove the front Catalytic converter is just not correct. Or indeed removing the centre one and keeping the front one.
It was and always has been my understanding that as long as the car meets current and the designed emissions standards for any car then you can delete either the front or centre Catalytic converters as in the MX5.
Likewise, you can modify the exhaust system as long as it complies with the noise (perhaps another topic)and the emissions.
People state BBR are correct is stating it will fail if you remove one.
That is not correct and in my opinion is a sales ploy, which is fine by me.
I have therefore contacted the DVSA for an answer.
Please see my enquiry and the reply I have received.
All a matter for your good selves, but some people will never accept this information of course.

I am wondering whether you can give me some help and advice on Catalytic Converters and Emissions for Spark Ignition Engines.
I have read sections in 8.2.1 as attached below, but to me and many others is a bit of a grey area.
Some cars have two catalytic converters and indeed some only one.

Those that have two fitted as an example may have one built into the manifold/header pipe and the other will be inline somewhere.

Some just have the two fitted inline within the system.

What I would like to know is what happens when someone wishes to fit a complete road legal stainless steel exhaust system.


Removal of the front header and catalytic converter and be replaced by a standard after market 4-1 stainless steel manifold.

Replace the centre OEM catalytic converter and exhaust section (or keep just the catalytic converter) and replace with a new one and stainless exhaust sections to tail pipe including silencers etc…

In doing so this would fully meet or exceed the current emissions and therefore pass the test.

Now as you also know there are many “after market type approved items” on sale that can be fitted legally to vehicles and still pass the current emissions tests for cars.

Indeed they are recommended as direct replacements.

Quite a few companies can supply or indeed build them to specification.

Having read the below, to me it is slightly confusing because of the part about “Emission control equipment fitted by the manufacturer, missing, modified or obviously defective”.

So can you replace/modify the exhaust/emission control systems with aftermarket components so that it still controls and complies with the current emissions standards?

Am I correct in saying that this was written to stop people just deleting the emission control systems altogether?

Also, if say a catalytic converter should fail then a person could replace with an aftermarket one which fits into the category of not being fitted as standard and obviously modified.

BUT is type approved and legal as far as the emissions test goes.

The same logic can be applied to the complete exhaust system.

Likewise it would be impossible for a Tester to know or understand the complete exhaust/emissions systems on all road cars.

So am I correct in saying the tester would inspect for a Catalytic converter and conduct an emissions test in the normal way?

I look forward to hearing from you.
Kind regards,


Exhausts can be a problematic area in the MOT test. This is largely because the test is based upon the relevant legislation and this sometimes makes it difficult to assess compliance where modifications have been made or aftermarket components are fitted.

Firstly, it is illegal to replace or modify an exhaust so that it increases the noise made by the escape of exhaust gases (Road Vehicles Construction and Use Regulations 1986 -Regulation 54)

It is also illegal to make modifications to a vehicle that increases the levels of exhaust emissions (Road Vehicles Construction and Use Regulations 1986 -Regulation 61A). This is not just the emissions checked at MOT test, but all emissions that that must be met as part of the type approval process.

Therefore, if an aftermarket stainless steel exhaust is fitted, the MOT tester will need to assess that the exhaust noise is not unreasonably above the noise level you’d expect from a similar vehicle with a standard silencer in average condition. They would also check that no emissions control components are missing, obviously modified or obviously defective.

*It is important to note that the regulations do not prevent modifications or the use of aftermarket components, including exhausts. The components are merely required to perform as well the OE components in respect of noise and emissions. If the design of the exhaust uses one catalyst where there were originally two, this is not necessarily an MOT failure, provided the system still meets the same standard for noise and emissions as the OE components did when in a serviceable condition. It may be necessary to show a receipt or other documentation to prove this, but like you say, most testers will not know how many catalysts were originally fitted.

In all cases, where there is doubt about whether a defect exists, testers should give the benefit of the doubt and pass the vehicle.

I hope this helps.
Best regards

Shaun Martin | Policy Specialist (MOT Testing Service)
Driver and Vehicle Standards Agency | Berkeley House, Croydon Street, Bristol BS5 0DA

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I’m not going to refer to legislation but from experience. During my phd i did quite a bit of engine testing. If memory serves me right a 3 way catalyst is positioned as close to the manifold as possible because the brake down reaction of the gases require the exhaust gases to be as hot as possible. If you move it further back it won’t work as good and if you check the emission requirements it wont pass the mot test The second catalyst i think its a particulate matter filter as well as further reducing the emissions.

Now if there is anything else in legislation that i am not aware i have no idea. When i was looking i just took what was referred to the difference between a race exhaust manifolds and a manifold with a catalyst is a price difference as well a performance difference between the two. It made sense to me and as i need the car to be road legal im going with a manifold that has a catalyst.

I accept your theory and agree.
It is still road legal if you don’t have one in the manifold as long as the “system” passes the noise and emissions for the car.
I reckon the front one was fitted for “other” markets that needed readings perhaps from start up.:man_shrugging:
The UK legislation and testing is different and therefore that is what must be applied.
Mine and many others pass the Mot with the standard Centre Cat (Mazda) or indeed an after market sports one.
The readings between the two set ups are near identical and well within the emissions tolerances for that car.
Of course what an individual does is entirely up to them.:+1::slightly_smiling_face:

Complete waste of time in my opinion. Your going to spend a lot of money for not much reward, been there & done it.
Either do it properly & spend around 5k & get a worthwhile 260bhp or keep it standard.

There’s also the issue that any management light warning is also an mot fail. And no well known garage would say, yes we will “fix that for you”. If you can bypass the management system / make it work or turn off the lights in the dash yourself thats a different story altogether.

To be honest when i used to own a 1.8L NA the ~100bhp yes it was never near enough for a sports car. With my NC I’m relatively more comfortable and the 2L engine gives out 160bhp which imho its more than enough for me for 1100-1200kg car. I’m not the guy who needs a fast car, i just want it to sound nice - and thats the essence of an mx5 - its the driving pleasure. And since I’m gunna keep this car for ever i don’t really mind fitting a stainless steel exhaust system for a mere +25bhp increase.

If it’s done properly the engine management light is not triggered :+1::slightly_smiling_face:

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So if you spend 5k and win 100hp you spend 1k for 20hp. If I spend 850 pounds for around 15hp, which means almost 18hp per 1k then it’s not worth it??

And that’s even besides the point of wether only numbers count, wether sound matters too and preventing the first cat from breaking down and clogging up the second cat (which happened to me) and response is MUCH better. So I spend around 1k when I’ve had my remap for:

  • 20hp
  • Better gas response
  • No more problems of precats breaking down and clogging up the main cat, which seems to happen more often on NC’s and which would again cost money to fix
  • No more whiney little ■■■■■ sound

I don’t even really long for much more power, that isn’t really all that usable on the small roads anyway and I wouldn’t want to make a mistake at 100mph. Besides, I wouldn’t want a turbo on this car either, I think N/A suits it much more and keeps it more reliable. I think that for a lot of people this would be a very good secure spending and it’s certainly no worse in terms of price/perfomance than 5k for 100hp more

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I am actually thinking of the Super 180 rather than the Super 185 from BBR for my NC. I am not much interested in high power at the high rev end (I won’t be racing my car), but better torque at the lower rev end (for acceleration at lights and when overtaking…at modest speeds…). There is not much difference in the torque curves in the rev range of interest and the Super 180, besides being a lot cheaper, basically only involves a new 421 exhaust header and a remap - leaving other bits alone. Any downsides to this ?

I’m no expert but I don’t particularly see any downside. you get the map and the manifold and +20bhp. The extra bits that I will have is the mid section, an end box and a less restrictive filter. +£1000 for a bit of bling, a bit of more noise and a bit of more hp. I think its a good compromise if you go for the 180 package.

IL 4-1 headers about £400
Ram Air intake £150
Ecutek remap £550

£1050 plus a bit of labour costs if you don’t want to fit your own headers or intake £300.

£2600 vs £1350. My car made 182hp with the above set up and really for noise the 4-1 headers are great.

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