NUTTYNICK

Another 'failed emissions' thread I'm afraid.

Loads of info on the site that has been useful but could do with some up to date confirmation

My car (MY95 wrx,Polar performance chip, 3" full decat exhaust) failed with a 0.52% co emissions at idle (and with a few revs). The other readings were in the green although, I cannot remember the figures.

It's passed all the other MOT's it's been through but I cannot say what spec the car was in for them ie, exhaust spec etc.

I'm looking at just biting the bullet and getting a Ninja sports cat so I don't have to mess around next time the MOT is due, plus trying something out then take it to the test centre only to have it fail again is going to be annoying.

Are there any sure fire tweaks, and will the CAT bring the emissions down?

Plus, can you wrap a cat or is it best to leave it open?

Ta

joz8968

iTrader: (13)

Well, first, you're not doing yourself any favours by getting it tested sans cat - you'd be extremely lucky if it got through! I wouldn't bother getting a sports cat either as they can be a bit marginal in getting the car through with respect to how much they cost - just go to somewhere like Zen and they'll temporarily swap out your decat for their own working(!) OEM cat for the MOT...

I also had a similar reading for idle. Please read about what I ended up having to go through at Zen's... https://www.scoobynet.com/scoobynet-...-boys-zen.html... before Paul finally got it through! That said, Paul did say that it was the hardest car for him to get through, lol.

The thing is, it could be anything that's causing the problem, typically - and as in my case - the O2 Lambda sensor, and/or one/some/all of the coilpacks.

Also, you need the patience of the garage to help get the car through e.g. by them taking it on a run to 'ignite the cat' and for them to rev it to keep the cat hot, whilst being measured by the machine (also as in my case). Indeed, it simply might be the case that if you get a decat on, go for a blat, and have the operator rev it on the machine, then it prob will get through, seeing as it's within limits on the other test parameters!

Honestly mate, if it won't go through with a working cat on, then all of the things I've mentioned above could be applicable to you too - so it's worth taking it to a tuner that's prepared to help you get it through... Your average high street MOT centre invariably won't be able/willing to help if it gets more in depth (as mentioned above), and you'll just be going round and round in circles and get nowhere...

The rookie

iTrader: (1)

CO2 with no cat at Lambda one should be about .67% so yours is about right, the centre exhaust section takes about 10 minutes to fit so if you can get one with a cat that will pass (just make sure you get it hot first - its a long way back from the engine, a wrapped downpipe helps!).

Simon

JohnD

iTrader: (5)

What did you honestly expect? you've got no cat!

JohnD

NUTTYNICK

From numerous posts on here reference imports, no exact match on the emissions machine's data base, and the fact that there are quite a few on here that state that they have managed to pass an MOT with no cat, maybe a pass

I showed the MOT guys the paragraph on the chart displayed on the wall ref the emissions of 0.5% co which he then went and tried. Trouble is, my car was 0.52% so still would have failed. He also said that the machine was set to a model not on the data base and it still came up with a pass being less than 0.3%. He said that the guys came down that week to re calibrate the machine which may have had something to do with it. Maybe the old loop hole law is no longer.

Don't get me wrong, I'm not some thick **** who expects things to pass with no cat, just that others have and I was wondering if things could be done. If a cat is what is needed in my case, so be it. But thanks for all the help, especially those that gave it.

NUTTYNICK

Cheers Simon,

I'm considering getting a sports cat downpipe as the guy did say that the car was illegal without a cat being the age (95). I just want a car that can be stopped by the feds and not be picked up for obvious reasons, plus one that will pass the MOT test. Do you reckon it will do the job? Promise not to hold you to your word

MMT WRX

If your car is pre 31st July 1995 then the CO2 is <=3.5

See this clicky

My Scoob, which is pre this date failed the MOT and Simon (GC8) posted this link.

If it is take it back to the MOT station and make them aware of this.

NUTTYNICK

Nice one, I've been looking for that page. Mine is way over on the CO emissions at 5.2% so have decided to fit a new lambda and sports cat in an attempt to rectify this.
Main reason for the cat was the fact that he stated the car had to have a cat fitted to be legal.

Fitting that soon so will report back later.

The rookie

iTrader: (1)

Eh, it was .52% now you say 5.2%...

Personally I would rather run an underfloor OE cat after a decat DP, than a sportscat DP, the cat is further from the turbo and the larger cross section would mean less back pressure relatively than the OE downpipe, plus its a LOT cheaper way of doing it! Either should pass the MOT style test, but if they introduce scanning roadside checks (no plans at the moment) sportscats won't pass that.

Simon

NUTTYNICK

Sorry, meant 0.52%

Why won't a sports cat pass the road side test?

Surely it has to be the same as MOT standards. I've managed to get hold of a half price Ninja down pipe so that will be going on soon, no more faffing about come next test time.

Plus I'd have thought the disadvantages of having a high cell count mid cat (oe type) negates the high cross sectional area compared to a sports cat with 100cel? That being the case, it makes no difference where it is in the exhaust system. Just my thoughts of course, nothing tested or conclusive

You are of course right about the price

MMT WRX

Well if it is pre 31/07/95 and 0.52 it should have passed without having to spend or do anything.

Take it back and get them to find the page in the link.

20withascooby

pre sept 95 no cat shud go through the mot no problems like mine did no cats