| On my 92 1.6 I'm experiencing severe loss of power at around 70mph, with the car being unable to do over 60mph up the slightest hills on the motorway. On going up hills and even on flats over about 75mph the engine tone is far deeper. There also seems to be a rattling from around the Catalytic Converter, on first starting the car and driving at low speeds. Could a damaged Cat mean a reduction in power, or are they not likely to be related ? Has anyone out there had to replace their Cat? Are they expensive ? Ant help or suggestions appreciated. (11/99) |
| I had exactly the same problems with my '5 some years ago. Sounds
like the cat melted. A new cat from Mazda is expensive, Moss do
a cheaper one. Before you put in a new cat you should find out why
your cat died, may be your ignition leads need changing too (broken
ignition lead = no ignition on one or more cylinders=> unburnt fuel
gets into cat, ignites and melts down the cat). If your car does not require a cat by law you could put a cat replacement pipe in, much cheaper but the car sounds more raspy. A melted cat, or a holed exhaust can cause serious power loss. Get it checked out immediately. Moss do a cheapish replacement cat and Jackson (I think) do a performance one. I had very similar symptoms on an MGB, years ago. Turned out that the timing had slipped from 10' BTDC to about 10' after TDC. The car still ran but was totally gutless and the exhaust note sounded 'flat'. It was quickly re-set and escaped damage to the exhaust valves. Another option might be that the cat has gone into melt-down and become partially blocked. Replacements are available from Mazda or (cheaper) Moss. If your car is pre '93 you can dispense with the cat altogether and fit a replacement pipe. Magnex do on for about £46.00 (11/99) |
| I had this happen on a Rover a few years back, quote from Kwit Fit " does it drive like a bag of spanners ?" me "er.. yes" KF " it's the cat then" (11/99) |
| I had mine checked - tapped a hole in downpipe upstream of the cat and used a pressure gauge to confirm excessive back pressure from knackered cat. (11/99) |
| I have a 91 Eunos which needs a new cat before its next MOT It has a JASMO stainless exaust, but the cat looks original and unaltered. It looks like I definitley need to fit one as there is a sensor on it. does anyone know where I can get one and approx how much to pay ? (11/99) |
| You don't need a cat at all. You can disconnect the sensor - it's just a temperature sensor and is not important. The cheapest option is to get a cat replacement pipe - about 40 from lots of exhaust places. If you really want a cat, get one from Moss. (But it won't have the tap for the temperature sensor AFAIK) The car will pass its MoT with no cat. (providing it's correctly tuned) (11/99) |
| You do not need a cat on a '91 car. You can replace it if you wish but it it is much cheaper (albeit not so green), to fit a cat replacement pipe instead. Magnex do one for about 45.00. AFAIK the sensor merely tells you, via a warning light on the dash, that the cat has overheated. You will probably pick up a couple of bhp as a bonus as well. (11/99) |
| If you can't get a second hand one, Magnex list one for about 45.00 (11/99) |
| Don't understand this at all. It is impossible - repeat impossible - for a post 92 (cat required car) to meet emissions regs without a cat. The regs are specific to the design spec for each car (although Eunos are in a funny position since the brand is not listed in the current computers). How can the guy know what the emissions would be without a cat if you had it tested with a cat fitted? It is also illegal to run a post 92 car without a cat anyway. Your risk! (11/99) |
| The rule on cats is complicated, but it is not illegal for a post 92 car to have no cat! It is only illegal for a manufacturer to build one without the cat. The MOT test only requires that post 92 cars pass a 'cat' test, The car does not actually have to have a cat fitted to pass the test, and some cars have such low emissions that they can easily pass without the cat. Just food for thought, I'm not suggesting you all bin your cats!! (Scimitar) (11/99) |
|
It is also illegal to run a post 92 car without a cat anyway. Your risk! ... '94 Eunos may not require a cat as it is not listed on MOT computers. I got by with this one this year and intend to lose my cat sometime soon (high flow DA 1.8 cat... one careful owner). So it is possible .. a little bit tongue in cheek as it is obviously an MX5 but with no computer listings it asks for minimal carb/non cat style emissions. .. and this stands for '93 and '92 .. but you have to have a helpful MOT tester. (12/99) |
| I fitted mine this morning, 45 from Demon Tweeks, claimed increase is 3-4 bhp, actual ???? Certainly feels quicker !!!! and definitely LOUDER. Only took 20 mins, including having to free the nuts off, so no real hassle if you have to put it back once a year. Hope I won't as I have a Oct '92 SE, had my MOT yesterday just in case and the guy didn't really care whether it was fitted or not, so I'll be using him again next year. (12/99) |
| Ive got a cat replacement pipe as well as an aftermarket exhuast system and have to say I didn't notice much of a difference, but thats probably due to the fact that I drive like an old granny in a Y reg metro - due to nearly killing myself 6 months ago in a rather nasty car crash :-( (12/99) |
| For the truly ignorant, what are the benefits of removing the cat and fitting a cat replacement pipe? (BHP gain I guess, but how much?) All this talk has got me thinking...! (12/99) |
| Removing you cat might give you 2 hp extra, at peak rev. In other words, top speed up. Not exactly what you're looking for on the street. I heard it also works as a filter for dirt, when you remove cat, bumper needs to get washed often, dirt flying out your muffler... I 've also been told the muffler get hotter without a cat -> muffler might break (a friend with the double postert muffler had this several times) (12/99) |
|
A CAT is totally wasted after 50000km, so if you leave it on or not doesn't make any difference at all. P.S. I'll never put my CAT back as I love the sound tooooo much as it is now (12/99) |
| Don't believe it, your cat is ok after 90.000km, at least mine is 100% ok!! I had it checked a little while ago at a diagnostic centre. (12/99) |
| On a similar theme, the heatshield around the cat is finally completely buggered and making a painful rattlling noise! Can the cat live without this sheild? Anyone running without one? Thanks for any adivce! (1/00) |
| I removed my cat shield totally, for the past 3/4 months. I've driven through various large puddles etc and all seems well, it passed its mot anyhow. So I would recommend binning it. (1/00) |
| The ex service-manager at a Mazda garage originally told me that their standard cure for rattling heatshields was to 'take the bu@@ers off' - they probably had a skip-full somewhere out the back. I never had a problem having it removed (when I actually HAD a cat that is - mine's in the 'bits taken off the car' box) hence I passed the suggestion on a while back. So the recommendation originally came from Mazda indirectly (1/00) |
| The Heat Shield does two things; Protect the bonnet/other components from excessive heat. Reflect heat back onto the manifold getting the operating temperature up quicker. This is to improve emissions. As previously stated, a Cat is most efficient >200 Celsius. (2/00) |
| Other rattles in exhaust could be the clamp from the gearbox bellhousing .. access through the LHS wheel arch. (1/00) |
|
I feel the need to get rid of the cat (definitely on the way
out). My query is I have a nice Jap Cat back system with 2 1/2"
Tubes a large step up from the down pipe, I suspect the cat diffuses
the difference quiet nicely. So should I Obviously the smoother the flow the better. Does anyone know if it matters enough to worry about? (1/00) |
| .. or D/ get a big 2.1/2" header so you can use a 2.1/2" FM cat ... ..yes steps cause problems but as you are going from small to large it is not a real big problem .. so 2.1/2" replacement pipe but if you are feeling beautiful get some weld laid in the 1st 1" + grind it down to create a taper over the first 1" of the pipe.. expensive in time and material... making a reducing cone pipe is a nightmare .. but you can get them ready made for some pipes (thinking hydraulic pipes here...).. not sure if you can in thin pipe .. then just add extension either end to match...(1/00) |
| www.dlralt.com Jackson racing cat replacement pipe...good for a few extra hp... Dealer Alternative took 3 days to get to me once my order had gone through.. about 10 days in total! (2/00) |
| Moss do em for just over 100quid - you tried them? www.mossint.co.uk (2/00) |
| Gut the pipe with a screwdriver ... this is not the final option as it is louder than a cat pipe .. but will tide you over. (2/00) |
| I replaced my aging cat with a 2.5" straight pipe. Improved top end loads, haven't noticed any drop off in low end torque. (2/00) |
| I have been told by Mazda dealer and MOT station that my 92 1.6 needs a cat. So I guess I'll have to refit. How hard is this? Access looks difficult, and working slap bang in the middle with just axle stands always worries me! (2/00) |
| So that's the symptoms taken care of, now I want to find out why it happened. So my question of the day is :WHY DO CATS MELT? (2/00) |
| I thought it was always down to the mixture being too rich. [makes mental note to fit an air/fuel meter!] (2/00) |
| Missed one vital cause.....HOLE IN EXHAUST SYSTEM before the Oxygen sensor. Because this in effect measures the combustion, i.e. Air/Fuel Ratio, because the sensor sees extra oxygen the ECU thinks the engine is running lean thus adds more fuel when in fact, within the combustion area (bore), combustion was actually O.K. More fuel = explosion type things going on in around the cat area = melt down. Holes are usually due to: rust, Cracked weld seams, leaking gaskets. Most people are ignorant of what effects holes have in the exhaust, especially since looking at a system it looks very prehistoric. (A lump of iron piping - or stainless). (2/00) |
|
Take something that aids chemical reactions (remember catalysts from Chemistry .. or were you one of the lot in the back setting the place on fire with bunsen burners, ethanol and acid..) .. get it hot (exhaust) .. then add excess reactive compound (petrol) .. and watch the temperatures rise until melt down occurs... .. so excess fuel ..could be duff ignition system, poor fuel, duff oxygen/lambda probe, duff ECU, duff air measuring system, sticking injectors (unlikely) .. CAI not altered the air sensor position? .. but it could have been done a while back and if plugs are alright and a good tan colour there is nothing too much to worry about. (2/00) |
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There are a number of reasons., Cats can melt due to continuing to drive with a misfire. This causes unburnt fuel to be exhausted into the tailpipe and depending on temperatures along the exhaust pipe, will ignite at some point. This is usually on the cat surface since this is the hottest point. Thus an 'explosion' occurs which can break the cat. Other causes are possibly 'thermal shock' which result from driving through puddles etc. hot-to-cold. Otherwise it may be due to poor throttle set-up; For efficient emission control the cat should be kept at >200 Celsius, preferably around 400-600. At WOT the ECU usually delivers extra fuel into the exhaust system which is unburnt, this cools the catalyst. (Don't ask me why misfires explode but overfuelling cools???-ask a combustion expert - I think it's to do with quantities). If your ECU does not see WOT then you don't get the cooling effect. (Note this is why fuel economy drops when driving hard). Also, the car is fitted with an Oxygen Sensor. This measures the amount of Oxygen in the exhaust and transforms this into a voltage. The ECU uses this voltage to add/reduce the amount of fuel, switching from lean to rich. if this is faulty then you are getting an incorrect mixture leading to incorrect combustion, leading to high temperatures. Catalysts melt down at approximately 1100 Celsius (melting point of the materials). Hard driving will see around 960 Celsius. (2/00) |
| Does anyone know exactly from what month in 1992, your car needs a cat to pass the mot ? With all the talk of the crankshaft problems on early cars I think my next car will be an early 1992 which would not need a cat. (3/00) |
| You need a cat if the first registration date was 1 August 1992 or later. Unless you buy a Roadster, of course - word is they aren't in the MoT computers, so get tested to a general spec and can pass without a cat! (3/00) |
| 1st August 1992 (ie first K reg) cars had to be fitted with a cat from new. Mine was registered 1 August!!!!! Remember, you don't actually need a cat, it just needs to pass an emissions test as though it has one! It is possible apparently. (3/00) |
| I'm going to put a cat replacement pipe on, as the JR cat has died. but the pipe has a hole for the sensor.. the JR cat has no hole so I got rid of the sensor (idiot) now I need one. If not what could I cover the hole with? (4/00) |
| Get a blanking plate made up (DIY), drill 2 holes for the retaining bolts and then seal with exhaust paste. BTW make sure you get a paste that works on cats, maybe something to do with heat but there are some pastes that are not recommended for joins onto cat. (4/00) |
| Someone spoke on the list a good while ago about hollowing out the cat on his pre-legislation 5. Anyone know how to do it ? (3/01) |
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1. take cat off car .. swear at the seized studs... The received wisdom seems to be that a proper plain tube replacement may cost a bit more but you get more power and a better quality of noise... (3/01) |
| I heard you just take a big screw driver to it. But the car runs better either with a straight through pipe (£20) or an off the shelf replacement pipe (Janspeed; built in resonator). (3/01) |
| CAT part numbers |
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From what I can gather there are 2 serial No series: From 100206: From 308212 |