Cat Bypass on a 1990 mazda mx5?

niceirishfella

hi,

does anyone know - will a 1990 jap import mazda mx-5 pass the nct with a Cat Bypass fitted?

thanks,

NIF.

JHMEG

Any pre September 1994 car will, as long as it's healthy to begin with.

Max_Damage

Your ECU may not like it, as there will be no information going to it from the oxygen sensor. I reckon it could be quite tricky dealing with the electrical end of it.

JHMEG

Max_Damage wrote: »

Your ECU may not like it, as there will be no information going to it from the oxygen sensor. I reckon it could be quite tricky dealing with the electrical end of it.

I'm sure some MX-5 guys here could answer if these is a sensor in the cat on that model. My '91 Integra had 2 in the exhaust manifold but none in the cat. (It did have an overheat sensor in the cat tho, which is only connected to a bulb)

Omcd

Have you asked them if they will allow this modification ?

I asked them about putting a rear wiper on a new dedicated switch on the dash (as it's cheaper than replacing the stalk switch), which I thought wouldn't be a problem, but they said it wouldn't be acceptable. They dont appear to have any flexibility when it comes to modifications.

JHMEG

Omcd wrote: »

I asked them about putting a rear wiper on a new dedicated switch on the dash (as it's cheaper than replacing the stalk switch), which I thought wouldn't be a problem, but they said it wouldn't be acceptable.

Presumably you were leaving the old dead switch in the car? I can see the problem with that.

colm_mcm

Omcd wrote: »

Have you asked them if they will allow this modification ?

I asked them about putting a rear wiper on a new dedicated switch on the dash (as it's cheaper than replacing the stalk switch), which I thought wouldn't be a problem, but they said it wouldn't be acceptable. They dont appear to have any flexibility when it comes to modifications.

A rear wiper isn't a requirement for the NCT, a seperate switch isn't a problem, whoever told you that gave you wrong info.

10-10-20

That's only if there is an O2 sensor downstream from the CAT. Unlikely with this age vehicle.

JHMEG

colm_mcm wrote: »

a seperate switch isn't a problem,

You don't think there's a problem with a labelled switch not working, and an unlabelled switch unbeknownst to anyone now doing the job? Usually for the NCT it's "if it's present, it has to work".

crosstownk

10-10-20 wrote: »

That's only if there is an O2 sensor downstream from the CAT. Unlikely with this age vehicle.

Agreed.

It's unlikely that a 1990 car would have a downstream sensor. It will have an upstream lambda sensor which analyses the oxygen content of the exhaust gasses before the catalytic convertor.

prospect

I did a bypass on my MX-5.

Any car built pre-1994 does not require a Cat.

The O2 sensor is not effected.

I did a quick service on my car before the NCT, oil, spark plugs & leads, etc. I also ran a dose of that cleaning agent through the previous tank of petrol.


It passed the NCT without any difficulty, and the emission figures were low enough to pass the 'newer car with cat' level.


Edit:
Also, I got my by-pass pipe from MX5parts.co.uk
The day I ordered it, I doused the Cats nuts (??) with WD40, and did so every day unit the unit arrived. I still ended angle grinding off two of them.

niceirishfella

Great.....thanks for all the info so far. I'm going to look at one this weekend.......

is there anything out of the ordinary that needs to be zoned in on with this car on a pre-purchase inspection?

Thanks.

galwaytt

niceirishfella - check yer PM's.


My '90 has no cat - doesn't need one at that age. And I didn't service it before last NCT, either.

Come to think of it, nor the one before that, either :eek:

Still passed, happily, though !