AliG

Having read many things on this board I was lead to belive that with only one of the 2 cats removed from the exhaust I would just get through an MOT all ok

Not wanting all the hassell of changeing bits over every year I replaced the back box with an Afterburner and the center with a resonated Magnex and left the downpipe as standard (MY93 WRX)

However I took it to be MOTed and the limit of CO is 0.3%vol and my car tested at a cool 0.9!!!! I asked him to retest and it came in at 0.6 but still nowhere close. Nolw with a bit of sweet talking and the right details put into the machine I have my MOT, but was wondering if this was normal or whatother peoples experiences were

cheers Alistair

*Sonic*

Mine flew through its first MOT, with std Downpipe, Magnex Res Centre & Magnex Backbox

what would scooby do

Mine flew through without ANY cats fitted

Find a "friendly" MOT station next time..

AliG

yes well, mine has its MOT as well so I think I found a Frendly MOT place however would be interested to here what CO figures you boys got ?

Alistair

*Sonic*

Heres my figures

Fast Idle Test @ 2746rpm

CO Level = 0.15%
HC Level = 13ppm
Lambda = 1.00

Natural Idle Test @ 779rpm
CO Level = .05%

greasemonkey

Ali, if you're going to test with a single cat, you need to get it well warm before it'll pass.

TBH though, this is one of the reasons why you might as well do the full decat. At least that way you know you're going to have to put 'em back on come MOT time...

AndrewC

My MY98 has passed (quite legally) twice now with only the center cat.

Andrew...

nom

MY93 WRX shouldn't need a cat anyway to pass the test - imports aren't described as on 'the list' so they only need to pass the non-cat test at that age.

EMS

Your lambda control doesn´t work properly or the cat wasn´t warmed enough. If for example your lambda sensor or MAF sensor isn´t O.K. the lambda control isn´t able to keep lambda @ 1. You never get good values in that situation!

Mark.

James_Harvey

Sounds like your Cat has died.
They only have a short shelf life!

James.

Pavlo

My car passed with just one 9 year old cat in place.

However, it could be to do with the fact a WRX doesn't always have 2 cats, the one in the centre pipe is just a resonator so It would be worth checking what you have. Just under centre hanger and foremost hanger on back box, then undo downpipe to centre join to look inside with a torch. A cat is obvious if it's in there.

Otherwise suspect Lambda could well be it.

Edit:

I read it wrong, you still have the downpipe cat in place. Something is wrong, as most jap imports don't have a centre cat anyway (certainly stis and some wrxs) and they pass emissions. Might be worth checking coolant sensor, or just making sure the cat is up to temperature when tested, the downpipe cat isn't usually a problem to get lit.

Paul

[Edited by Pavlo - 7/21/2003 6:55:33 PM]

*Sonic*

My figures above where with a decat centre, and a faulty lambda, as I had to replace it a week or so afterwards

AliG

so providing the cat was warm enought I could have a faulty Lamda or Maf sensor?

what other symptomes should I be loking for? as I don't seam to have another problmes that I am aware of (touch wood)

can I test the signal from the sensors with a multimeter etc to conf they are ok

Alistair

Leslie

It could easily be a tired Lambda sensor Ali. I have got a single sports free flow cat in the centre pipe. It failed the MOT first time quite badly. I replaced the Lambda sensor and it went through very easily. On the 2889 RPM test, CO max 0.00% HC 6PPM Lambda 1.00
Natural idle CO max 0.01%. Its a MY94 STI. Its also worth checking that there are no exhaust leaks anywhere, that will kill the pass as well.

Good luck anyway.

Les

[Edited by Leslie - 7/23/2003 4:55:28 PM]

Pavlo

check the MOT emission result to see what the lambda was for the test. If it's much under 1.0 it suggests the lambda sensor is to fault, as the ECU will generally try and correct the AFR on idle.

Paul

Smiler1

Was the MOT place using the 0.3%vol limit setting from a MY93 UK car?

If so then even with a cat an import WRX wont pass that, as they are mapped for Japan and the emission's can be much higher.

Most MOT places dont know have the figures for the import cars - so make sure it was tested against the correct figures before you start replacing stuff.

Cheers

S with a cat free MY 94 WRX