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Topic: CATs - buy new, used, or just remove inside of it? (Read 1479 times) |
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MS
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CATs - buy new, used, or just remove inside of it?
« on: Apr 21st, 2005, 9:57pm » |
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Hi,
Please advice, is there any sence to remove CATs?
Mine right have gone, now there is the question - to buy new or just remove it? How engine management will behave after I remove it? As I know, there are 4 lambdas - 2 before cats, 2 after.
If the only solution is to buy new - any ideas for inexpensive original or aftermarket copies for it?
Thanks,
MS
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Eric_R
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Cosworth Owner 1998 - 2006 & site co-founder
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Re: CATs - buy new, used, or just remove inside of
« Reply #1 on: Apr 22nd, 2005, 11:18am » |
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MS
If you have the 24V then you have 2 catalysts, one on each exhaust manifold. They work to remove CO and hydrocarbons from the exhaust and are checked using the lamda (HO2S) sensors to ensure that they are working properly. See http://www.fordscorpio.co.uk/ho2smonitor.htm for an explanation.
You might knock out the centre of the catalysts, but then no emissions reduction will take place, the post-HO2S sensors will be switching at the same rate as the pre-cat sensors, and DTCs will be stored. However, there is no Check Engine (MIL) on the SCorpio so there will be no visible sign.
However, come the next MOT there is very little likelihood that the car will pass the emissions test. Both CO and HC will be far too high.
I would change the catalysts and keep your car legal- there are OM parts available at about £170 each side. In some cities there are roadside emissions checks and your car would certainly be seized and towed away if it had no catalyst action at all.
I wouldn't bother with 2nd hand ones. The action of taking them out of a scrapped car would probably break the ceramic element inside and it would be a waste of effort IMO.
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MS
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Re: CATs - buy new, used, or just remove inside of
« Reply #2 on: Apr 22nd, 2005, 1:33pm » |
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Thanks, Eric!
MOT is not a problem, I reside in Eastern Europe,
no sensors on the roads here at least for next 3 years 
The questions were about negative things as extra noise, fuel consumption, idling problems, etc....
What do you think about installing "universal" - I mean when will be used "general type" catalysts and soldered to old pipes? Any suggestions, I mean noisy, hard to fit, impossible to fit, something else?
Here univesal CATs priced around 50-60 GBP/each (depend on it's form and size) + max. 10GBP/Hour job.
Regards,
Maxim
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OHC
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Re: CATs - buy new, used, or just remove inside of
« Reply #3 on: Apr 26th, 2005, 9:41am » |
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Hallo!
I have the same problem! My DOHC is suffering from cat rattle and I'M going to remove it! As far as I know post-cat Lambda doesn't affect fuelling at all! The only problem if DTC generated will invoke LOS affecting performance and MPG! I've read in the Forum it won't!
Eric, please, I need your tech advise! I have no money even for aftermarket cat that won't last long on awful Russian petrol! Luckily MOT Is not a problem here!
Best regards,
OHC
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SaveTheNight
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I can resist anything ...except temptation !!
 
 
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Re: CATs - buy new, used, or just remove inside of
« Reply #4 on: Apr 26th, 2005, 12:18pm » |
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no problem with removing it OHC < other than the law related to cats in your country>.... and you won't invoke LOS .....regards ...STN
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Octavian_P
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Re: CATs - buy new, used, or just remove inside of
« Reply #5 on: Apr 27th, 2005, 7:36am » |
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is there a performance increase if the cats are removed 
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SaveTheNight
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Re: CATs - buy new, used, or just remove inside of
« Reply #6 on: Apr 27th, 2005, 7:40am » |
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yes .. you are effectively removing a restriction .. and also a slight economy advantage too .. STN
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Octavian_P
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Re: CATs - buy new, used, or just remove inside of
« Reply #7 on: Apr 27th, 2005, 10:22pm » |
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This sound great, knowing that when i bought my scorp and registered it, i know it was put into no-cat group, so why not take advantage of this. Is there something special to do at electrics (lambda probe) if i eventualy remove them ??
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mr._floppy
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Re: CATs - buy new, used, or just remove inside of
« Reply #8 on: Apr 27th, 2005, 10:48pm » |
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Is there not a substantial relaxation in the emission test part of an MOT for cars over a certain age ? the reason being an engine with 200 000 miles on it can scarcely be expected to be as " environmentaly clean " as a new engine.
Or does that only apply to Non - Cat Convertor Cars?
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Steve_S
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1997 scorpio ultima 2.9 24v lpg
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Re: CATs - buy new, used, or just remove inside of
« Reply #9 on: Apr 28th, 2005, 2:34am » |
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Noise factor may increase after knocking out the guts. I am about to do one of mine as its been rattling for over 2 years now and it finally caused powerloss last week which luckily cleared after giving it a whole lot of wellie .
My emissions with one rattling failed cat 14 months ago tested when on petrol only just passed. If both cats were out there would be no way it would have got through an mot.. Luckily I have the option of LPG and it sailed through on that 2 months ago 
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Steve S
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SaveTheNight
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Re: CATs - buy new, used, or just remove inside of
« Reply #10 on: Apr 28th, 2005, 7:53am » |
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Octavian_P ... you leave the wiring and lamdas alone .. they still have to compensate < providing they are working > ... STN
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Eric_R
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Re: CATs - buy new, used, or just remove inside of
« Reply #11 on: Apr 28th, 2005, 4:16pm » |
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MS and OHC,
If emissions are not tested in your area, then there's no problem with knocking the catalysts through. You may have a struggle taking them off, because they run very hot and the bolts tend to fuse together on the downpipe. Be careful how you get them off, because striking the manifold hard will damage the HO2S sensors, and you still need them. You might consider welding up a replacement pipe to take the place of the catalyst, as is done on pre-1992 engines here, and this option would also be quieter.
As STN rightly says, you still need the HO2S sensors because the front ones control the fuelling. If nothing is detected from either of them then the fuelling will be in Open Loop and you will use a lot of fuel as the engine will not be on proper lamda.
The trick is to prevent the EECV detecting that there is no catalyst at all. If the EECV sees the rear HO2S sensors switching at the same rate as the front ones it will progressively cut back the fuelling to minimise emissions (it's prime directive) and you will lose power. You might leave the sensors in place, but remove the wiring and arrange some electronics to put 0.4v into the sensor wires. A steady voltage will fool the EECV into thinking that the catalyst action is very satisfactory, and you will get maximum power.
There will be DTCs because the EECV will not detect any heating circuit on the rear sensors but these can be ignored. ALternatively, leave the heater wires in place on the rear HO2S sensors and just bring the 2 sensors wires from each into the cabin, where they can be fed with the 0.4v, switched by the ignition.
In this way you would get no DTCs at all, you would get fuelling for maximum power and you wouldn't be wasting fuel running rich all the time.
RH post cat sensor wires are white/blue, brown/blue
LH sensor wires are white/green, brown/green
Leave the other two wires in place on each - these are the heaters.
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Octavian_P
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Re: CATs - buy new, used, or just remove inside of
« Reply #12 on: Apr 28th, 2005, 9:34pm » |
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All this wireing gives me a headache, last time when i've changed a fuse, i wasn't able to start the car for about a week, hmmm probably i'll wait a bit more, till the cats are out of the game and then do the trick.
Anyway this cat problem helped a lot of understanding the role of lambda's. This also solves another "problem" at another type of car. A friend of mine got out by mistake the lammbda wire from it's exaust, and that engine worked so crappy.....till we found why.
Verry nice site/forum and polite users, best regards to you all.
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Steve_S
Full Member
1997 scorpio ultima 2.9 24v lpg
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Re: CATs - buy new, used, or just remove inside of
« Reply #13 on: Apr 29th, 2005, 4:38pm » |
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Quote:| back the fuelling to minimise emissions (it's prime directive) and you will lose power. You might leave the sensors in place, but remove the wiring and arrange some electronics to put 0.4v into the sensor wires. A steady voltage will fool the EECV into thinking that the catalyst action is very satisfactory, and you will get maximum power. |
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All previous posts and info regarding the rear lambda have indicated that this sensor took no part in engine management other then to monitor, since when has this changed?
If this sensor has now suddenly decided to become part of the management system then if it was disconnected apart from throwing up an error code would not the management revert to the front sensor resulting in correct fuelling again??
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Steve S
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OHC
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Re: CATs - buy new, used, or just remove inside of
« Reply #14 on: May 3rd, 2005, 7:48am » |
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Hello!
Eric R, and what if I just disconnect rear HO2S! The PCM will try to push it enriching mixture and if no avail will set a DTC, won't it? as far as i understand it happens once per drive cycle. So can I disconnect post-cat HO2S cause it doesn't affect fuelling. It won't swithch at all not misleading PCM! And DTC won't invoke LOS!
Best regs,
OHC
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SaveTheNight
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Re: CATs - buy new, used, or just remove inside of
« Reply #15 on: May 3rd, 2005, 8:12am » |
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OHC .. just leave the sensors exactly as they are and wired .. you won't invoke LOS and won't notice any difference except maybe a little more power being catless .. and slightly better economy being catless .. thats it !! ..regards ........... STN
Eric's answer was meant for duplicating exactly the circumstances to convince the electronics that the cat is there and working ... hence near perfect fuelling and power .. <if everything else is in order >.. but you have been driving with far less than perfect fuelling for a long time I would imagine .. along with many of us .... cheers
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Eric_R
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Re: CATs - buy new, used, or just remove inside of
« Reply #16 on: May 3rd, 2005, 7:51pm » |
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Steve,
We have only said the the post-cat sensors play no part in fuelling - not that they are not any part of engine management.
The post cat sensors are there to check that the catalyst(s) are working correctly. In some OBD programming the rear cats can be switched to take on the role of the front ones if they fail - we are not sure if ours do that yet.
The post cat sensors are there in order to comply with the full OBDII.
The situation is that if OBD detects the same switching on the rear sensors as the front then the CATALYST monitor will detect it and cut the fuelling back. This won't be anything as bad as LOS - this is really drastic - but it will work hard to minimise pollutants and this will result in a loss of power.
If the rear sensors are disconnected altogether then the CATALYST monitor will not be able to run. The problem there is that this may again induce the OBD to cut the fuelling right back, safeguarding pollution and the catalysts, even though they aren't there.
My own choice would be to provide a small voltage on the rear sensors, but as STN says, if performance is not an issue then just leaving them there would be the next best thing. He won't get the best out of the Cosworth, but it will run smoothly enough.
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Octavian_P
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Re: CATs - buy new, used, or just remove inside of
« Reply #17 on: May 7th, 2005, 9:11pm » |
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on Apr 27th, 2005, 10:48pm, mr._floppy wrote:Is there not a substantial relaxation in the emission test part of an MOT for cars over a certain age ? the reason being an engine with 200 000 miles on it can scarcely be expected to be as " environmentaly clean " as a new engine.
Or does that only apply to Non - Cat Convertor Cars? |
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Sorry for not repplying, i was out of town for a week. In my country Romania, it's a big headache to register a car, if it's new or old, you must get it to RAR ( romanian auto register), they do a identification on it. In 96 when the car was bought there was no "euro" constriction in polution, so the car was simply registered, after this appeard euro 1 and 2, and now on ther's euro 3 and 4 restrictions classes. So if you registerd for example an euro 2 capable car in a non euro class (no-cats) it stayies so. If now i want to change it's class i need to re-test the car as it'll be a new "prototaype" of car, so RAR establish the polution class, regardless the type / brand etc, this operation costs, and takes a lot of time, so why the heck not leave it like so. Also by time cat's wear out, so the engine, in no cat class will pass easier the periodical technical inspectins ( MOT how u say). Otherwise, there are just some classes for no-cat, and euro cat cars, in wich thers a threshold in polution. It's kind of stupid because if you have a euro 4 class car and it's emissions are of euro class 3, you will need to fix it to give euro 4 emissions, or to "change" your engine and re-test it (prototype). So again why bother soo much.
By the way wich euro class corespond to scorpio ? 2.3 16V.
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Steve_S
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Re: CATs - buy new, used, or just remove inside of
« Reply #18 on: May 21st, 2005, 3:45am » |
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thanks for the reply guys. There appears to be more confusion in the UK over cats now. I was speaking to an MOT examiner a few days ago and he says the latest MOT equipment now tells the examiner if the cat is present or not. An examiner will now fail a vehicle whether or not the emissions are OK if a cat is not fitted or the guts have been knocked out of it. Can anyone confirm this or shed more light on to the current 2005 situation?
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Steve S
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martin_rowe
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Re: CATs - buy new, used, or just remove inside of
« Reply #19 on: May 21st, 2005, 8:36am » |
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No the test equipment can not tell if a cat has been removed, as far as the MOT test is concerned, the presence of a cat is not a testable item, you just have to meet the emission levels, which you can't do with out the cat anyway.
Martin
(Authorised Examiner, Quality Controler, Nominated Tester)
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