NC 2.0 Exhaust Manifold

Hi if the exhaust manifold is swapped on the 2.0 ltr NC for a 4 into 1 and egr delete will the car still pass the MOT test ? 

Best Regards Joe 

Yes it will passs

Yes I think will pass an MOT with only the 2nd cat in place today, however the MOT rules are changing in may and may include a visual inspection for original equipment fitted

I reckon it’s going to be pot luck because there is no way any mechanic could know what was originally fitted to every car ever made. Some of the changes will be invisible without dismantling too. I would think if it passes the emission test and doesn’t look obviously “wrong” they will pass it.


Bear in mind you’ll need a remap to remove the hazard light on the dashboard after removing the cat. :slight_smile:

Mine was fitted by BBR, their set up with the single CAT was fine to pass the MOT and it certainly helps the car breath.

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Unfortunately the new MOT rules pertinent to this are not about exhaust emissions.

Where a cat(s) or DPF(diesel particulate filter) should be fitted to a car, the MOT inspector should check that it is physically there.

A large number of cars are fitted with a close coupled or maniverter cat as well as an underfloor cat, the MX5 NC is just a typical example.

In theory the obvious absence of the maniverter on your MX5 will be a fail, given the new rules,  in my opinion.

As I understand, the rules previously in place required a cat or DPF to be fitted to the vehicle where originally specified. This allowed the legitimate removal of the maniverter provided the car passed emissions, as a cat(underfloor) still in place. The new rules require both cats to be in place, regardless of emissions.

How this will actually affect you is yet to be seen. With luck it will be some time before the new rules are rigidly applied and this mod will not cause immediate issue.

My advice is take the car to MOT as usual but have a plan B if pulled up on this. Appear shocked if/when it fails but be in a position to quickly retrofit the old maniverter if required.         

This is it bang on 

simply because there is no information available as to the fit and position of oem cats for a tester and I doubt there ever will be .

Not if you relocate the second sensor behind the remaining cat it wont