which ones work and which ones dont work?
i used to have a ninja one on my old wagon and it passed one mot,power was upped to 315bhp and then it wouldnt pass an emmisions test.it was brand new and i paid £300 for it,i felt like id been had!
im considering purchasing another one (not ninja) as the catted downpipe seems so restrictive.
i definetely dont want to decat because i cant be bothered with hassle at mot time.
ive heard the h&s ones work but they are silly money.
i would be running about 300-320 bhp on a 98 sti type r mapped with apexi.
are there any solutions that are cheap and cheerfull that actually work?

 

My mates got a spare il enquire for you .

 

cool,but does it work?

 

nobody know then?

 

It depends on what you'd call "working". The idea is to reduce the restriction that comes from having the matrix in the exhaust gas flow. If you use a 100 cell cat for instance, the larger holes in it allow greater flow, and hence the potential for more power output. We've fitted a 100 cell cat that flowed enough for over 500 bhp easily.
The cat also has to reduce the CO output by some .5% to enable an MOT pass. That's the tricky bit in some cases. So far, we've found that if they are well wrapped, they work.
There are legislation issues with cats being fitted to cars after 1999 I believe, when they should strictly speaking be fitted with type approved cats. It's on the statute books, but not widely enforced. Yet.
We can supply sport cat downpipes for £265 delivered. For racing use only of course!

 

ive come to the conclusion that if a sports cat downpipe is fiited to a classic impreza running 300bhp and it dosent pass an emmisions test then whats the point in having it?
you may as well decat surely?
i know they all state that they will pass an emissions test for mot.....but they didnt on my wagon.
so the hassle of changing a decat pipe and fitting the cat back on at every mot time now seems like it worth the hassle,because you could go out and spend 300-500 quid on a "decent" sports cat on the basis that you dont want to keep changing at mot time,to find the fookin thing fails with your £500 sports cat on.

 

We've had them fail on stock cats as well!
Welcome to my World, where nothing is easy.

 

what would be the reason for this alan?
running to rich?
surely if the car is mapped it shouldnt be running too rich/lean,so it should in theory be simple practice to swap the downpipe over to original cat and it should pass.....unless the cat is fooked?

 

Theoretically yes. It isn't about mapping if the closed loop lambda is enabled.
The sensor constantly runs between "rich" and "lean" when it's operating, if it's a stock four wire lambda. It should run between .1 and .9 of a volt, keeping the mixture averagely correct at Lambda 1 or 14.7 AFR. That normally runs out at around .5% CO which is the bit that's scrubbed out by the cat. If you have Emission figures at .5 CO, HC at around 50 ppm and Lambda between .97 and 1.03 the cat isn't working.
If you have high HC the motor normally isn't running right. If you have lambda below .97 it's rich, and the sensor will show a constant high voltage. If the lambda figure is above 1.03 it's nominally lean, which could be due to intake or exhaust leaks.
Wide band lambdas use a different operating principle but the effect is the same on emissions.
We had all that going on with a Scooby this week. It needed a cat for MOT. We fitted a second hand standard one, which turned out duff. We fitted another one, that was duff as well, but it made me check the car out again, being unexpected. It took a third second hand cat to sort it!
Naturally enough, nobody wanted to fit a new one!

 

cheers alan,im gonna go for a decat and then change back at mot time,if the cat fails,then fair enough i may have to buy another second hand cat as a new one will probably cost a fortune and it would only be used once a year....i think the chances of buying 1,2 or 3 "duff" cats are very unlikely.
you could probably pick up 5 second hand cats for the price of a new one.
thanks for the info,these sports cats aint all that and i think the majority of them are a waste of money,mine was red hot when last tested and still failed at two seperate mot test stations.
i know a few people on here dont have any problems with their sports cats at mot time,but my luck is never that good.

 

We always run those options past our customers. I suppose you could take the view that it's trouble all round regardless and just flip a coin! At least my chaps are pretty good at getting cats on and off..

 

time for me to start practicing,or if im feeling flush ill pop it down to you once a year.