Removing Cat converter

[joanie]

Can anyone tell me if removing a catalytic converter from a car with
electronic ignition involves having to reprogramme the computer? Or can you
just hack it out
Cheers Joan H

[WiM]

Depends on which year your car is...
Mine is a 1991 and there is no sensor in the CAT, my father's is a
1997 and it has a sensor in the CAT. Obviously without the sensor it
is question of swapping for another cat or a cat by-pass. Some cat by-
pass have a threaded hole for the sensor too.
NOW there is something else that has to be taken into account; on
tech control of the car examiners might 'miss' the CAT and let the
car fail because of that. In Ireland you only need a cat as from 1994
so before that you can happily take it out of the car. In Belgium I
am not allowed to take the CAT out at all, so here we use a different
technique: shove a straight pipe up the cat (stop giggling in the
back!) and weld it in situ. From the outside it looks like a normal
cat but it actually is a cat by-pass...
WiM

Quoting Graham&Joan Hilder <graham.joan@paradise.net.nz> on Wed, 23
Nov 2005 23:33:57 +1300:

Can anyone tell me if removing a cata
lytic
converter from a car with
electronic ignition involves having to reprogramme
the computer? Or can you
just hack it out
Cheers Joan H


WiM
'91 1.6 MX-5 (due to immigration for sale)
www.mx5ireland.com
www.cardomain.com/memberpage/312875

[Simon Lord]

All of which raises the question: "Is there no SPCA in Belgium?"

Simon
Franchise New Zealand magazine & website

[rod.brown]

Installed in some catalytic convertors is the oxygen sensor which is a
vital engine management system (EMS) part that is needed to maintain the
engine in optimum petrol burning condition. The EMS is cabable of making
changes to fuel and ignition systems to ensure a correct air/fuel ratio at
all times. The EMS needs to know how much oxygen is in the exhaust gases
and makes its decisions based on this information. Remove the CAT, remove
the sensor and the EMS will know, running the engine in what is called
"open loop mode".Factory specd to 14.7/1 air/fuel with new motor.
Given that everything else is in good order ie all other sensors working,
no air leaks ie loose oil filler cap,loose oil dip stick etc, then you
will probably not notice much or any change.(unless of course someone has
already played with settings of say, the air flow meter to counteract
suspected faults).
Given all this then the quick answer is NO,reprogramming is not needed.
Rod Brown

[Brady]

I'm really glad this topic is up, as I've been contemplating removing the
cat from my '91 for some time.
Why can't that 2nd oxygen sensor be "re-installed" at the point in the
exhaust pipe where the cat used to be?
Bradyzoid

[Lyndon]

Two questions: Are you sure that removing the O2 sensor will make the fuel
inj system run in 'open loop mode'? Why would running in open loop mode all
the time not be a bad thing to do?

Lyndon.

[Okibi]

Removing catalytic converter's rates up with neons, fluffy dice and sticker
horsepower.

Sure you get the slightest improvement, but there are usually VERY harsh
fines if you get caught. IMHO it's just not worth it.

The catalytic converter is there for a reason.

If you really think your cat is restrictive, do the job properly and get a
high flow one fitted.

If you want to be a back yard mechanic stick a 20 kilo bag of cement in your
boot, it creates GREAT stealth downforce ... honest

My 2 cents.

- Dave.

[poison]

Good point, but what are they converting their Cats into over there?

A serious question though... I had Belgium fries at a Belgium bar in the
city... looked and tasted a lot like French fries, and every other kind of
fires I have tasted... was there some subtle... taste sensation I was
missing there???

Gazza
"PO1SON"

[zorruno]

on 24/11/2005 9:17 p.m. David wrote:

Removing catalytic converter's rates up with neons, fluffy dice and sticker
horsepower.
Sure you get the slightest improvement, but there are usually VERY harsh
fines if you get caught. IMHO it's just not worth it.

Sorry, are we talking about NZ still? Unless something has changed in
the last few months (?), it is not illegal to remove a Catalytic
converter. It likely is in other countries, but please remember this is
a NZ focussed list, so a bit of clarification is always helpful. I'm
not sure of the legality of fluffy dice however (it may be different
with various Council bylaws).

Whether it is sensible however is up to the individual, I doubt the
gains are much (I've seen dyno figures of 2-3hp touted around), and
there are issues of change in exhaust tone, oxygen sensors in later
models, killing trees etc.

A couple of other clarifications, Eunos models (at least up to 94, and I
assume 97 and probably later) do not have a dashboard check engine
light. So if you don't reconnect an oxygen sensor at a Cat, you
probably won't notice unless you connect up an ODB checker (an expensive
LED) to the ECU connector. US models flash a big light on the dash to
say 'you've done something bad - get me to a mechanic'.

There is no reason why you can't just reconnect the oxygen sensor back
into a straight pipe, or small muffler - some of them come already
threaded.

Personally, I like trees, reduced carcinogens and not spending lots of
money on small power gains so my cat stays...

cheers
H

[Lyndon]

But are they worth replacing when they get old? Clogged up, glowing red and
pushing Back up the pipe. Would you replace or discard?
Lyndon.

[Mark O'Sullivan]

On the issue of catalytic converters:

If your car has completed more than 100,000 km, the catalytic converter is
no longer doing it's job - certainly the case by 160,000km. Throw it away
and replace with a resonator and ground the cat sensor - any muffler shop
knows what to do. All perfectly legal in New Zealand.

If you would rather replace the cat with a new one - try looking at the
price - they aren't cheap.

Cheers
Mark

[WiM]

Hehehe we actually do


Quoting Franchise New Zealand <simon@franchise.co.nz> on Thu, 24 Nov
2005 07:01:02 +1300:

All of which raises the question: "Is there no SPCA in Belgium?"

Simon
Franchise New Zealand magazine & website

[WiM]

CATs go bad after 2-3years anyway, so we all should change them every
coupla years if you want the gains (nature wise)from the CAT. The
thing with the cat by-pass is that there is no longer the restriction
of the material in the cat. This results in a better flow of the
exhaust fumes and so your engine loses less power by pushing the
fumes through CAT, result more horsepower (2bhp).
WiM

Quoting zorruno <admin@mx5forum.co.nz> on Fri, 25 Nov 2005
11:56:28 +1300:

on 24/11/2005 9:17 p.m. David wrote:

Removing catalytic converter's rates up with

neons, fluffy dice and sticker

horsepower.
Sure you get the slightest improvement, but

there are usually VERY harsh

fines if you get caught. IMHO it's just not

worth it.

Sorry, are we talking about NZ still? Unless
something has changed in
the last few months (?), it is not illegal to
remove a Catalytic
converter. It likely is in other countries, but
please rem
ember this is
a NZ focussed list, so a bit of clarification is
always helpful. I'm
not sure of the legality of fluffy dice however
(it may be different
with various Council bylaws).

Whether it is sensible however is up to the
individual, I doubt the
gains are much (I've seen dyno figures of 2-3hp
touted around), and
there are issues of change in exhaust tone, oxygen
sensors in later
models, killing trees etc.

A couple of other clarifications, Eunos models (at
least up to 94, and I
assume 97 and probably later) do not have a
dashboard check engine
light. So if you don't reconnect an oxygen sensor
at a Cat, you
probably won't notice unless you connect up an ODB
checker (an expensive
LED) to the ECU connector. US models flash a big
light on the dash to
say 'you've done something bad - get me to a
mechanic'.

There is no reason why you can't just reconnect
the oxygen sensor back
into a straight pipe, or small mu
ffler - some of
them come already
threaded.

Personally, I like trees, reduced carcinogens and
not spending lots of
money on small power gains so my cat stays...

cheers
H


WiM
'91 1.6 MX-5 (due to immigration for sale)
www.mx5ireland.com
www.cardomain.com/memberpage/312875