Well i've taken the plunge and got myself a new cat and the best part is it comes with a pre cat where the usual standard aftermarket crap doesnt ....... now im praying im going to finally get shot of my cat efficiency code when i get it fitted some time next week ...... other thing is do i need a gasket set for it as it says you musn't use exhaust paste upstream of the cat ....
http://i509.photobucket.com/albums/s337/Prozmonkey/29052009009.jpg

Proz....

Is that the one that was on ebay a couple of days ago?

If so mate,can you please take ALL details from it...i.e maker,part numbers etc......i emailed the one on ebay but he pushed for my registration number so i didn't bother,i beleive it was made by a company in Nottingham
Also can you tell me for definate if the front sensor bolts directly into the pre-cat? i have a explanation for the codes

MonzaIain wrote on 29. May 2009 at 20:25:

If so mate,can you please take ALL details from it...i.e maker,part numbers etc......i emailed the one on ebay but he pushed for my registration number so i didn't bother,i beleive it was made by a company in Nottingham Also can you tell me for definate if the front sensor bolts directly into the pre-cat? i have a explanation for the codes

I got it from here .....
http://stores.shop.ebay.co.uk/BuyPartsBy__W0QQ_armrsZ1

I think there part number is 90794

It has a lambda hole before the pre-cat and one after the main cat just before the bend in the pipe .

What is your explanation for the codes ?

Cheers


This is the actual one

http://cgi.ebay.co.uk/Cat-Catalytic-Converter-Vauxhall-Omega-2-2i-16v-99_W0QQitemZ270399215700QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item3ef50c9854&_trksid=p4634.c0.m14.l1262&_trkparms=%7C301%3A0%7C293%3A1%7C294%3A30

I got mine for less than £130 all in including postage ..... getting it put on for £30 .... i just hope it cures my P0420 code  :y

The original cat on the car would have had the 2nd lambda after the pre-cat not after the main cat, so this hopefully will do the job as everythings going through 2 cats before the 2nd lambda does it's reporting.

Seen this for sale too and have been considering it.

Hope it works!

Ok,i did a bit of online research and also spoke with a guy over here who makes stainless systems

The first sensor is effectively no use because...... on the factory set up the first sensor takes the measurement from the 'swirling' gases from within the pre cat box.
After it has been through the main cat and treated the measurement is then taken from the 2nd sensor.

As the aftermarket pipe has no pre-cat the gases travelled too fast 'past' the 1st sensor for it to take an acurate measurement.....

Both sensors measures in voltage so because the first sensor doesn't get an acurate reading the voltage fluxuates too wildly to be 'within tolerance' for the system of the car...

The set up should be...

1st sensor....voltage with rise and fall wildly
2nd sensor......voltage will be more constant

Because the 1st sensor is not getting a proper reading then the 2nd sensor will rise and fall wildly because it has nothing to compare it with (from the 1st sensor)

The EML will come on because the car's system registers that there is an emmision problem due to the fact that the first sensor is not getting a proper measurement reading,however it wont flash up a fault with the sensor because it is there and it itself is functioning properly

wrote on 29. May 2009 at 20:51:

The original cat on the car would have had the 2nd lambda after the pre-cat not after the main cat, so this hopefully will do the job as everythings going through 2 cats before the 2nd lambda does it's reporting. Seen this for sale too and have been considering it. Hope it works!

Yeah i really hope it works  :-/

MonzaIain wrote on 29. May 2009 at 20:53:

Ok,i did a bit of online research and also spoke with a guy over here who makes stainless systems The first sensor is effectively no use because...... on the factory set up the first sensor takes the measurement from the 'swirling' gases from within the pre cat box. After it has been through the main cat and treated the measurement is then taken from the 2nd sensor. As the aftermarket pipe has no pre-cat the gases travelled too fast 'past' the 1st sensor for it to take an acurate measurement..... Both sensors measures in voltage so because the first sensor doesn't get an acurate reading the voltage fluxuates too wildly to be 'within tolerance' for the system of the car... The set up should be... 1st sensor....voltage with rise and fall wildly 2nd sensor......voltage will be more constant Because the 1st sensor is not getting a proper reading then the 2nd sensor will rise and fall wildly because it has nothing to compare it with (from the 1st sensor) The EML will come on because the car's system registers that there is an emmision problem due to the fact that the first sensor is not getting a proper measurement reading,however it wont flash up a fault with the sensor because it is there and it itself is functioning properly

The original set up has lambda before and just after the pre-cat so hopefully on this set up its going through both before the second sensor so should be nice and clean  :y

The 2nd sensor is after the main cat is it not?

MonzaIain wrote on 29. May 2009 at 21:02:

The 2nd sensor is after the main cat is it not?

The second sensor is behind the main cat on this one but i belive on the original spec fitted at production the second was just after the pre-cat .... but i may be wrong  ..... maybe one of the admins would know what the original set up would have been :y

I think its got to be after the main cat mate.....

Thats how it measures the emmisions is it not? once it has been treated by the main cat?

I thought it was the pre cat that did the main cleaning up of the gasses and the main cat cleaned up anything that was left ..... one sensor before the pre and one after then gave the pre cat code when it lost its peak efficiency ......
Anyway on my new one the second lambda is after the main cat so it should be "cleaned " twice and hopefully stop the P0420  :y

There was a long thread on here a while ago about moving the second lambda to behind the main cat to help as well so thats why im sure the second was just after the pre cat on original set up  :y

Hope so mate....if it works i'll get one

When you doing it??
;D :y

MonzaIain wrote on 29. May 2009 at 21:14:

Hope so mate....if it works i'll get one When you doing it?? ;D :y

Should be sometime this week coming so i'll let you know  :y

on the v engine, and 99% sure the 4pot as well, the order is... sensor, pre act, sensor, main cat.

The acknowledged fix is to move the 2nd sensor from between the 2 cats to behind main cat. Usually done by welding in a new 02 sensor boss and plugging the old hole with a sump plug or similar.

I guess the part Proz has is pre modified with the sensor pre positioned after the main cat to save welding. Should work if Albatros's fix is anything to go by.

There are some theorys as to why the code is raised in the first place. The usual guess is the pre cat is damaged or no longer efficient. On the v6 there was a theory that a batch of faulty valve stem  seals where allowing oil into the combustion chamber and tripping the code, either on emissions or by cat contamination. See the off with its heads thread by mark dtm on mick dundees car.

Anyway, in theory, that part should work. :-)

I guess my theory is a bit off the mark then.........

However it has to do with the temperature i think.....the pre cat will heat quickly,where as the pipe without the cat wont,therefore the sensor wont get a true reading...
The reason i say this is because,when i went from my house to Hotel21's,which is about a hours drive,we got about halfway there,the EML went out on its own....
So i think it has something to do with how hot it is/going to be

However it has to do with the temperature i think

Yes i think you are right .... mine failed the mot on natural idle but passed the fast idle when nice and hot ..... anyway if this doesnt cure it i will change the O2 sensors even though i dont think there is anything wrong with them and if that fails then its swan vesta time  ;D

or drill and plug your original cat..?

Well new cats been on for 2 days now and I/M monitor reports cat monitor ok and no light so hopefully .... where as before the instant readiness wouldnt complete and it would put the eml on with the cat code .... so looks like this might cure my P0420 .

Praying no more light  :y

MonzaIain wrote on 29. May 2009 at 20:53:

Ok,i did a bit of online research and also spoke with a guy over here who makes stainless systems The first sensor is effectively no use because...... on the factory set up the first sensor takes the measurement from the 'swirling' gases from within the pre cat box. After it has been through the main cat and treated the measurement is then taken from the 2nd sensor. As the aftermarket pipe has no pre-cat the gases travelled too fast 'past' the 1st sensor for it to take an acurate measurement..... Both sensors measures in voltage so because the first sensor doesn't get an acurate reading the voltage fluxuates too wildly to be 'within tolerance' for the system of the car... The set up should be... 1st sensor....voltage with rise and fall wildly 2nd sensor......voltage will be more constant Because the 1st sensor is not getting a proper reading then the 2nd sensor will rise and fall wildly because it has nothing to compare it with (from the 1st sensor) The EML will come on because the car's system registers that there is an emmision problem due to the fact that the first sensor is not getting a proper measurement reading,however it wont flash up a fault with the sensor because it is there and it itself is functioning properly

Well he needs to stick to maiking exhausts then as he clearly has no clue to what lambda sensors do!

The first sensor is THE most importnat one, it is providing feedback to the ECU to effect mixture control.

The second oen is teh redundant one, it does nothing more than monitor the state of the pre-cat....

MonzaIain wrote on 30. May 2009 at 09:26:

I guess my theory is a bit off the mark then......... However it has to do with the temperature i think.....the pre cat will heat quickly,where as the pipe without the cat wont,therefore the sensor wont get a true reading... The reason i say this is because,when i went from my house to Hotel21's,which is about a hours drive,we got about halfway there,the EML went out on its own.... So i think it has something to do with how hot it is/going to be

Lambda sensors do not work until hot and the cats dont work until hot either. But, lambdas have heaters in them to get them upto temp much quicker.

The idea of a pre-cat is its small and gets hot quick so works faster and hence meets emissions requirements on the heat up cycle

Marks DTM Calib wrote on 02. Jun 2009 at 13:15:

MonzaIain wrote on 29. May 2009 at 20:53: Ok,i did a bit of online research and also spoke with a guy over here who makes stainless systems The first sensor is effectively no use because...... on the factory set up the first sensor takes the measurement from the 'swirling' gases from within the pre cat box. After it has been through the main cat and treated the measurement is then taken from the 2nd sensor. As the aftermarket pipe has no pre-cat the gases travelled too fast 'past' the 1st sensor for it to take an acurate measurement..... Both sensors measures in voltage so because the first sensor doesn't get an acurate reading the voltage fluxuates too wildly to be 'within tolerance' for the system of the car... The set up should be... 1st sensor....voltage with rise and fall wildly 2nd sensor......voltage will be more constant Because the 1st sensor is not getting a proper reading then the 2nd sensor will rise and fall wildly because it has nothing to compare it with (from the 1st sensor) The EML will come on because the car's system registers that there is an emmision problem due to the fact that the first sensor is not getting a proper measurement reading,however it wont flash up a fault with the sensor because it is there and it itself is functioning properly Well he needs to stick to maiking exhausts then as he clearly has no clue to what lambda sensors do! The first sensor is THE most importnat one, it is providing feedback to the ECU to effect mixture control. The second oen is teh redundant one, it does nothing more than monitor the state of the pre-cat....

Well actually that was my theory really......
I'm no expert on exhausts or Lambda's...so,
sorry

Marks DTM Calib wrote on 02. Jun 2009 at 13:18:

MonzaIain wrote on 30. May 2009 at 09:26: I guess my theory is a bit off the mark then......... However it has to do with the temperature i think.....the pre cat will heat quickly,where as the pipe without the cat wont,therefore the sensor wont get a true reading... The reason i say this is because,when i went from my house to Hotel21's,which is about a hours drive,we got about halfway there,the EML went out on its own.... So i think it has something to do with how hot it is/going to be Lambda sensors do not work until hot and the cats dont work until hot either. But, lambdas have heaters in them to get them upto temp much quicker. The idea of a pre-cat is its small and gets hot quick so works faster and hence meets emissions requirements on the heat up cycle

So am i correct in thinking then that, because the pipe on mine just now wont be hot enough to get a reading then?

Hence the reason the light is coming on?

The reason i was getting it was the cheap crap VX fitted .... it had no  pre-cat .... mines been fine since the one above was fitted  :y   .... best £130 ive ever spent to get rid of that light ... :y

Aye,i know the solution/fix for it mate....

Was just trying to get a reason behind it that was all and MarksDTM seemed to no more than me..

:y