What can I do?

My Eunos 1993 manufactured cars catalytic converter is broken. It was one of the cheap ones from MX5PARTS and has only lasted about a year and as a result has failed its MOT. I have enquired from the local Mazda dealership about getting a new OEM cat. from them but they have come back to me and said that they are now obsolete and Mazda do not have any. So my question is, does any one know of a company that produces a decent catalytic converter as the ones supplied by MX5PARTS are a waste of money.

You could try MX5Bitz, I think it’s a guy on here Rhino666?

And check that the fault that caused the replacement cat to fail is fixed.

Also, as a 1993 import, you can decat the car.

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How do I convince the MOT tester that this is indeed the case.

Does this help. I think there’s a copy of the MOT flow chart in one of the posts on
emissions, but I can’t find it. Hopefully a knowledgeable person will be along soon

and another helpful one

You need to establish that the car’s not an MX-5, it’s a Eunos Roadster, and that a 1993 model is from the 3 year “transition period” (from August '92 to July '95) when cars not listed in the Annex to the In Service Exhaust Emissions book still get given a non-cat test.

The first bit is just a matter of looking at the VIN stamped on the bulkhead in the engine bay. For MOT purposes, each model of car is identified by its “VDS Code” which is the 4th to 9th characters of its VIN. If the tester looks in their copy of the In Service Emissions book they’ll find the VDS codes for each model of MX-5 but since Eunos Roadsters have a quite different format of VIN, your VIN will produce a nonsense VDS code which doesn’t match any listed model.

If the tester then follows the flowchart in the MOT Testers Manual they will note that since it’s a car from the transition period not listed in the Annex, that they should give it a non-cat test.

The biggest hurdle is persuading the tester that no, it’s a real thing and you’re not trying it on, and that no, they shouldn’t just take the computer’s word for it that your car is some model of MX-5; that’s just what some previous tester mistakenly clicked on - look at the VIN!

If they still really doubt you, ask them to phone their DVSA (formerly VOSA) contact who will tell them it’s legitimate.

Hope that helps

PS As above, it’s worth considering why the cat failed (or even if the cat failed) it might be a failed sensor instead - the lambda sensor and coolant temperature sensor can each cause emissions failures if they are faulty.

Just had a look at decat pipes as an alternative, on mx5Parts. Part of the description states,

“Please Note: As from January 1st 2012, the UK MOT laws changed regarding catalytic convertors. Any vehicle built after 1992, MUST have a catalytic convertor fitted regardless of whether or not it passes an emissions test. Any car presented without a cat fitted will fail. We would advise checking with your MOT tester before fitting this pipe if the car is being used on the road.”
Is that true?

It’s not entirely correct.

It is true that any car which needs to pass a full cat test must now also have a cat present; it’s no longer enough to just pass the emissions, the car is inspected to see that the cat is fitted and it fails the MOT if it isn’t.

It’s not accurate that this means “any vehicle built after 1992”. It applies to almost all cars registered first used from August 1992 (i.e. J-reg or later) but unlisted models in the transition period, including Eunos Roadsters, get 3 years’ grace. i.e. it only applies to Roadsters from N-reg onward.

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Thanks, I did wonder
:thinking: so OP could possibly get something like that and job done. :+1:

Yes, a decat is an option (so long as the emissions failure is minor and won’t also fail the non-cat test) but decatted cars are noisier and smellier as well as more polluting so it’s not ideal. Cars without cats are a bit like smoking in pubs: we didn’t really notice just how 'orrible it was when it was normal but going back to how things used to be would be a shock.

And there’s a moderate chance Polyanna’s cat isn’t the problem. When you say the cat is “broken” Polyanna, what did you mean - actually broken as in falling apart or did it just fail emissions? If the latter, can you let us know what the emissions numbers actually were, as that might be a clue to a cheaper repair. If it would also fail the non-cat test (3.5% CO and if I remember correctly 1200ppm HC) then it ain’t the cat that’s the problem, it’s probably a sensor.

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If I remember correctly this is the flow chart you need.
They carry out a BET, if it fails then they have to find an exact match of the VIN in the EGA database etc.
The Eunos VIN is not in there only the MX5, some testers use the default MX5 values, which as I understand is not correct as they should then perform a non cat test.
Hope this helps, been there, done that and got the tea shirt.

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The cat rattles inside when the engine is running and the tester said he twice tested it try to pass its emissions test without fail.

Are the Eunos MK1 exactly the same as the MX5 Mk1 ?, If they are does the reply that I got from the dealership that there no more cats being made for the Eunos, mean that the same applies to the UK MX5 version of the Mk1. I just had a thought that if the above is not true would an MX5 cat fit a Eunos Mk1

From mx5Parts website.

"Quality aftermarket replacement catalytic convertor. Mild steel construction, hi-flow core. At least equal to the original in both quality and efficiency.

Fits all Mazda MX5 UK cars AND Eunos Roadsters"
I would be asking for either a new replacement or my money back! If its only lasted a year but they claim it’s at least equal or better than OEM. It also states they fit all models so yes, should be OK. I reckon though that this would be the same answer, discontinued.



1.6 JDM catalytic converters are dimensionally the same, but have an additional 1-time sensor. When I last checked, the Mazda price of a JDM cat was roughly 2x the UK cat at around ÂŁ600. At one time, Mazda dealers could only order a UK spec part upon receipt of a UK VIN.

All Mk.1 Eunos Roadsters (1.6 and 1.8) use the same cat, which is the same size as the cat fitted to '89-'93 1.6 MX-5s (and commonly referred to as the 375mm cat) but it has this extra heat sensor in the tail.

All the sensor does is light the “Heat” lamp in the dash if it gets so hot that its internal fuse melts. It’s been commonplace for years to use an ordinary MX-5 cat if you need to replace one of these special Japanese ones. Without a sensor, the Heat lamp stays out permanently.

The cats, JDM 1.6 v JDM 1.8, aren’t quite the same, but close enough.

1991-93 Eunos Roadster 1.6 cat: B6BR-20-600, 86,000 yen. Interestingly, for earlier cars, the part number is B63H-20-600B, and the price is about 70,000 yen. What was the change?
1993-95 Phase 1 1.8: BPF3-20-600, the list price in Japan is about 60% of the price of the 1.6 version, odd, so something significant changed. 58,000 yen.
Same part for the short lived Phase 1.5 model.

For late 1995-runout (Phase 2 cars) 1.8: BPR3-20-600A, so it changed again, and again got cheaper, 43,000 yen. The engines in these were slightly more powerful, and different engine management.

Source: http://do-da.co.jp/sun-mec/partslist.html

I wonder if a 1.6 cat is too restrictive for a 1.8. Mazda dealers, if entering a VIN, sometimes will be “computer says no”, rather than recommending fitting a 1.8 JDM cat to a 1.6 car, or vice versa.

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My mk1 Eunos is from 1991 so doesn’t need a cat but a couple of years ago I was running a silenced decat and didn’t like the noise so replaced it with a new cat from a Uk manufacturer, I’m trying to find the name & address in my old paperwork. The company was very knowledgeable and the quality of parts was very good. It was under £100 and it fitted my JDM spec. Still working as far as I know as it just sailed through it’s MOT.
I still have the old cat somewhere the reason I didn’t use it was that the mating faces of the two ends were corroded and needed re-finishing so it was just easier to get a new one.

I’m in agreement with Barrie, if this cat has fallen apart in less than a couple of years then there is a very good chance of you getting it replaced under the sales of goods act which says that things should be expected to last a reasonable amount of time. If you’d spent 12 quid then 18 months would be reasonable but I’m sure you spent considerably more so should expect it to last a bit more than 1 mot.

Edit. Its the consumer rights act 2015, superceded the old sales of goods act.


Re: cats and MOTs. My understanding was the current rules stipulate it must have what was fitted in factory, regardless of the emissions regulations it must meet.

For example, my 1991 UK spec came with a cat but does not have to meet catted emissions, but must still have one present as it was factory fitted.

Is my understanding correct?