Cat removal legality + performance gains?

Hi all,

I have a 1993 Eunos roadster (imported in 2006), and I think it’s still got the original catalytic converter on it. I’ve been reading into the legality of removing the cat (apparently it’s ok since it’s a pre-1994 import?).

  • On the car documents it’s listed as a Mazda Eunos 1600, so if what I’m reading is correct this means there’s no UK equivalent and the car can be de-catted?

  • I’m hoping to sell the cat and get some performance gains from de-restricting the exhaust and some money for other mods. Am I right that this should be an easy bit of extra performance (maybe at the cost of some noise)?

Some pics of the car to make this wall of text easier on the eyes :slight_smile:


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I don’t think you’ll get many upgrades from selling a MK1 cat

I’d check with a CAT specialist 1st for that old 1600cc one. Might not be in same league cash wise as the ones getting knocked off. It’s not the CAT as a whole…it’s the rare earths inside which varied.
BHP.? Two miniature Shetland ponies with arthritis on a good day. One might be asleep. You won’t notice.
Noise? Wholly depends on what you fit in the CAT’s absence.

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Haha cheers @IanC , @Scottishfiver

A good friend who knows these well also warned me the 1.6 NA cats are probably “worth f**k all” haha.

Hey I’m an optimist - one or two lame ponies is probably a 4% HP gain on this! :smiley:

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Ya gorra larf a bit sometimes eh?

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I was going to be optimistic and say you’d get half a tank of fuel, but 2 lame ponies may be the best you’ll do!

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I’d be more worried about the chassis rails.:roll_eyes:

Looks like they were crushed by a forklift when imported. Never been brought up on MOT for some reason.

No rust at all though which is surprising - it was undersealed well at some point

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Not seen them that badly mangled but if the MOT man is happy👍

Yeah I know they’re pretty bad - I’m going to get them fixed and extra chassis braces added at the mx5restorer soon :slight_smile:

Gonna take good care of this one!

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It was fit when new then it’s a legal requirement to have a cat. MOT might also pick it up because emmisions will probably fail.

Removing the cat also means it will need a retune.

Roy

Can you offer some technical & evidential links to your information pertinent only to elderly Mk1s?

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Yeah what Roy’s saying is contrary to what I’ve read but ofc I wanted to ask here as I’m sure there are others who have removed the cat from 93/94 import roadsters.

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Like me in my 93 1840cc.
It was fine…bar the increased din and always passed MOT gasses…legally sans CAT… under the prescribed import criteria.
Prepared to be “schooled” on it even aged 69 but I’ve never in 15 years with the marque read or heard of the need to retune a Mk1. Funny old world…maybe I missed it.
Anyway…that’s me done now. :wink:

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I’m no expert with Mk1 MX5’s but sure as hell if you change the exhaust gas flow it is likely to impact on the exhaust ‘suck’ from the cylinder head; it will be less noticed with less racy cams. Only real way to find out is do a before and after run on a rolling road.

Every change to my kit cars exhaust systems I have always stuck it on a rolling road and not once has it ever not needed adjusting.

If removing the cat means you acheive more suck then an injected car it is very likrly to run leaner, mix that with E10 and who knows.

Not my engine so it is your call and hey, I may be wrong!!

Roy

PS … take a read here, it may be of interest.

Roy

Scottishfiver, I hope these links/downloads are of interest:

Info regarding emmision standards can be downloaded from the .gov site … Google search ’ In Service Exhaust Emission Standards’ for Road Vehicles should find a PDF.

Also the IVA manual for M1 type vehicles is also worth looking at when modiyfying cars and can be downloaded from here:

Generally I would be more concerned with ensuring that by removing the cat it does not mean the engine runs either too rich or too weak. At the MOT they normally only check the emmisions meet the requirements for the vehicle reg/model etc.

Roy

Hi
I have a October 1992 1.6 Eunos import. I removed the cat ( as it was dead) 5 years ago & fitted a silenced stainless decat ( from Autolink ) & Moss Cobalt exhaust. Car has a nice raspy exhaust note, car runs beautifully. Never had a problem with the MOT, I just tell the tester it is Non Cat test as an import.

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Cheers mate this is exactly what I needed to hear. Might pick up that decat pipe myself… Hopefully the cat is worth enough to cover the cost of the pipe at least! Haha

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I’ve also recently removed mine and changed for a silenced bypass pipe from Mx5 Parts. I’ve not tried to sell it yet, but could not see a code on the cat (which would’ve helped value it). I have noticed a nicer exhaust tone, albeit a bit more smelly!
Apologies if you don’t need this advice, but it definitely helped me when someone told me to soak the 4 bolts with WD40 several times before removal, and always use a 6 sided socket for removal, as opposed to 12 point, as they are usually solid to undo and rounding off would be a nightmare…

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I’d imagine zorst nuts & bolts that have been through hundreds of thousands of heat cycles, water, salt, mud and snow over a few decades might decide to be a tad stubborn.
I know I would be.
My Missus gives my neck bolt a dose of this every night.

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