Hi there!
Has anyone come across a 355mm long catalytic converter with over heat sensor it’s on an 1.8 NA eunos roadster 1994?
I would be interested in your experiences of anything like this
Yes Andrew, that is a standard Eunos Catalytic converter 345 -375mm.
The sensor is a one time fuse that blows when the cat overheats.
What is the problem? I sell these, original Eunos spec with facility for refitting fuse or UK spec, the same part without the fuse facility.
Thanks for your reply and some more information on the overheat part and how it works.
The problem is before my ownership the rear section was replaced. Looking at it logically the front hanger was welded to the flange near to one of the stud holes , when it was on the car. The heat from the weld has expanded onto the cat stud( which is snapped to half its length anyhow) making it impossible to move the rear section off the cat to repair a poor seal.
Since it’s been blowing I have a rattle maybe the cat but I shall clamp the heat shield on the down pipe to eliminate that possibility.
I can’t quite picture what you’re describing but I’m reminded that partway through Mk.1 production, one of the exhaust hangers was deleted, and I think it’s the one nearest the cat.
The result is when I’ve bought stock exhausts over the years for my 1993 Roadsters, they’ve come without this one hanger pin, so I had 5 rubber hangers under the car but only 4 pins on the exhaust to hold.
Not a big problem when you learn that Mazda just deleted it, since you just don’t use that hanger any more and it’s fine. But it rather sounds as if someone has decided to weld a new 5th pin to a stock exhaust and they’ve done it in a way that obstructs the cat fittings. If that’s what the issue is, I’d probably just hacksaw off that pin and do without it.
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I’d say Martin is spot on but…
There are two parts that are very similar.
- the early catback for the 345/375 early short cat that has the extra hanger welded to the front flange and…
- the later catback for 1995-7 cars with a 435mm cat where the catback is very similar, in fact interchangeable but no hanger on the front flange.
As said that rear hanger by definition is not required but someone obviously decided to add it. You may find that the flanges will need some work to stop the blow if distorted.
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There were 3 sizes in the MK 1’s production life, a small from 1989 - 1994/5 370mm, a medium 1995 - 1996/7 440mm and a large 1996/7- 1998 475mm .
These can vary a little if JDM or UKM.
A J ltd 1.6 will be a 370mm. a J II ltd 1.8 should be a 370mm.
M-m
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From the 1996 model year. The problem is that some MOT testers might think there is a missing hanger, and the exhaust is not secure.
Exhausts like Mongoose came with a hanger as a seperate part, held on by the cat bolts.
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Mazda part numbers for JDM:
NA6CE up to 113545: B63H-20-600A
NA6CE from 113545: B63H-20-600B
(a suffix generally indicates a part is backward compatible)
From NA6CE-200000 (the Phase 2 1.6 models)
B6BR-20-600 (yen price is 20% more than the earlier part, so I assume these might have significantly more honeycomb)
NA8C-100000 (early 1.8s)
BPF3-20-600 (yen price is way cheaper than earlier 1.6 cats. Note completely different part number)
No change for NA8C-300000 (Phase 1.5 1.8’s, ie the R-Limited and RS-Limiteds)
NA8C-400000 (Phase 2 1.8s, effectively the final iteration of Eunos Roadster
BPR3-20-600A; the cheapest cat ever fitted to a Eunos Roadster (half the price of the late 115hp 1.6)
Add to that, perhaps a fallacious assumption that all Eunos Roadsters with a overheat sensor must be factory fitted. Its entirely possible that an aftermarket part was fitted in Japan. Some Japanese aftermarket parts are of horrific quality, and you might even get garages taking universal JDM cats, and welding on flanges.
There are variances in cat length on 1.8, because some are perhaps unaware they are trying to fit the part to the wrong car.
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All Eunos 1.6 and 1.8 cars, the popup headlight models, have a factory fitted 345/375mm cat with a onetime fuse. It is simply a onetime fuse, so apply heat and it melts, end of part and replacement needed for purity. Never heard of a Japanese aftermarket cat of any sort, let alone one with this facility. Many of the originals are still out there including the one on our 1991 Eunos.
In truth the fuse is not required and only ever fitted to Japanese import cars like the eunos, some Imprezas and probably a few other Jap imports. Uk equivalent of the same time period did not have this fuse fitted.
Most replace the Eunos cat with the UK equivalent without the fuse, cheaper and easier with no real compromise.
Never heard of an MOT failed because this hanger is missing. Either the system is secure or it isn’t for MOT purposes. Most also remove the hanger mount(two bolts) to tidy up, if a part without the hanger is used.
The third type of catback fitted to the later UK spec cars only, 1997-8 is around 50mm shorter with the longer cat and bespoke front pipe. I get a lot of customers replacing the longer cat and associated front pipe to fit the earlier UK spec version(435mm) and associated front pipe, for the purpose of adding an aftermarket catback. Very few of these available, direct fit, for the longer cat.
In summary, three lengths of cat, all with bespoke front pipes. Three different bespoke catbacks but the two that fit to the shorter cats are interchangeable. It’s a bit of a minefield, particularly when owners buy the wrong parts and then modify to fit. No problem at the time but an issue when a subsequent owner and another new replacement part required.
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The " heat sensor" on the JDM cats can simply be unplugged, it makes no difference to the MOT or regs here, it was a JDM reg thing back then for their country not ours, plus the imports should be tested as an import at MOT time “NOT” a Mx-5 ,and this must be pointed out at testing with the tester before the test starts for inputting info into the testers computer system, that is very important, The hanger thing??? that is more the zorst from the cat back and is not a fail, as some had them and later did not, never ever had any get finger pointed by the MOT man as you mix and match systems, tell him he is over keen and talking tosh, and use some “common sense”.
Just as a foot note:- early MK 1 roadsters don’t even need a cat to pass when the tester does their job correct .
FYI…
http://www.mazdamenders.net/forum/viewtopic.php?f=17&t=6611&p=57378&hilit=cat#p57378
M-m
Thanks for all your input.
I am pleased to say a new catalytic converter has been fitted and the car is running well.
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