m j s

i've just had my '94 wrx mot'd, it's got a blits air filter, hks down pipe, magnex de-cat center pipe and rear box. there is no catalitic converter on the car and it passed the emissions test with flying colours, the results are as follows:

co % voloume 0.91 limit(3.50)
hc ppm 126 limit(1200)

and the mot'er did not say anything about the catilitic coverters missing!
i was worried about the emisions before the mot but as you can see the readings were well low.

David Lock

m j s

I think you have been lucky! Those results are from a non-cat test. The rules re cats come down to when car was registered and if your car was before August 1994 you may not have to have a 'cat fitted.
BTW the cat test has 2 read-outs at tick over and fast idle (around 2500 rpm). David

Pete Croney

Interesting point.

I got the RA MOT'd a little while ago. We had fitted a twin cat centre section and got it nice and hot for the gas test.

The MOT tester took one look at the car and said he could not test the car. The reason was the lack of normal seat belts. He then took some details of the car, including what the model was (Subaru WRX RA) and rang the DOT.

They advised that the harnesses were fine, provided they were BS or FIA marked and in date. They also advised that the car was not on the emissions database and a the car had to be tested as a NON CATALYST vehicle.

It would have passed, but the point is if you turn up and let them test the car as an Impreza Turbo, they will apply the emmission figures for a UK car. If you describe the car as a Subaru WRX or STi, then it will not.

Cars that have been SVA'd have an Emmission Certificate which gives more generous emmission allowances, but again the test stations have no way of testing to these limits. The machine will give a pass or fail on the data it has.

David Lock

For those interested the DoT will happily send you FOC a copy of "In-Service Exhaust Emission Standards for Road Vehicles". Comes from DoT Bristol on 0117 951 5151. I have an August 1996 version but I was told this morning that the latest edition is July 2000. My version is 40 pages of detail giving exhaust limits for 99% of vehicles. For info my version lists Impreza 2000 Turbo and the limits are:

At tickover (between 800 and 1000 rpm) CO max 0.5% HC max 200 ppm

At fast idle (between 2500 and 2700 rpm) CO max 0.3% HC max 200 ppm

Lambda reading must be between 0.97 and 1.03 and min oil temp 80 degrees C.

Note these limits may be superceded by latest standards. As Pete says the fun starts when your particular model is not listed.

Actually these limits are quite generous as a properly functioning 'cat should just about remove all CO (turns it to CO2) and HC. Taking the cat out would almost certainly mean that you could not tune the engine to run reasonably with say less than 0.5% CO at tick over which would mean, technically, you are breaking the law on a vehicle registered after 1 Aug 1994.
Note is not a legal requirment to have a 'cat but it is a requirement to meet the emission standards laid down and a 'cat is about the only way to do that. I personaly think that cats are an environmental con. They cost a fortune to replace, use semi-precious materials, don't work until the engine is hot and probably worsen mpg. David.

pat

Just out of interest, a while back I checked the emissions on a a friend't tester, to see whether it would be possible to pass the emissions test with a PossumLink and no cats. The verdict was that it WAS possible to get both CO and HC emissions below the limit, but that the lambda was a tad high, about 1.18 IIRC, which would have failed a cat test...

Recently I got my car through MOT, and this was on a Pectel engine management system running closed loop lambda and idle control with parameters I "guessed" as being close.. idle was a little erratic, but it passed :-)

Pete's dual cat centre section is a great piece of kit, being a centre section it can be switched out in about 10 minutes, so if getting a car through MOT perfectly legally (including cat test) is quite easy :-) Just pop down to Scoobysport, they'll swap over the centre section, go pass your MOT then they'll swap it back....

Cheers,

Pat.

AnthonyJ

My 98 WRX has just failed its emissions test on CO - 0.85 at fast idle and 1.22 at natural idle. Does anyone have any idea what may be causing that?

The lambda was spot on( 1.008) and the HC was really low (32-50) so I'm not sure if it is a Lambda sensor or the cat or something else. The car is completely standard apart from a PE T75 downpipe that was fitted recently (my turbo blew so I thought I'd get it changed while I was there!). I don't suppose that could have anything to do with it could it? Where is the Lambda sensor situated - could it have been damaged in the process of changing the downpipe.

I'd really appreciate any help or advice anyone could offer...

firefox

Mine read 3.39 CO at fast idle.. LOL

But a bit of "tweaking" got it through the test

J.

Pete Croney

Does your downpipe have a cat? A cat turns CO into CO2. If it failed the test and does have a cat, either the cat has failed or is not efficient enough for your car. Was everything warm?

Your lambda is working fine if the readings were 1.008.

AnthonyJ

OK - kind of embarrassing! Having done some checking around, you are entirely correct Pete - the downpipe doesn't have a cat. Sorry about that - what an idiot!!

I'm assuming then that the WRX doesn't have a cat in the centre section which leaves me with a bit of a problem - I'm about to replace my standard WRX centre section and backbox (no cat) with a nice shiny new HKS system (no cat). I'm sure that 364 days of the year this will be fantastic (no cat!), but one day every year I will need to find a centre-section with a cat in it, or some alternative way of getting my car through its MOT. (I don't think changing the downpipe each year is a particularly great way of getting round the problem)

Firefox - how did you "tweak" your car so it went through the test?! How does everybody else manage this? Am I doomed to have to spend more money on a pipe I use once a year or is there some trick to this?!

Pete Croney

Anthony

The answer is above. Re - read my first post on this thread.

David Lock

Dare I mention that another option would be to consider the use of the Broquet Fuel Catalyst (which we supply). This will greatly reduce CO and HC emissions because it improves the combustion process. I have had Broquet installed in my own 1989 Peugeot 1.9i since it was new. It will pass the 'cat test emission/s limit even though it doesn't have a 'cat in the exhaust. This is pretty good going for an engine with 142k on the clock. I can't guarantee that Broquet will do the trick for every engine but it will certainly help. If you need any more info please e-mail or telephone (01403 823507). Cheers, David