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A usual dilemma when someone changes the exhaust system, is what to do with the stock catalyst. D14 engines have a ceramic catalyst which someday it will have to be changed. The stock catalyst is very strong and will pass emissions even after 150K++km if it is used properly (right a/f ratios, good quality of gas etc.) Still many of us consider whether the stock catalyst will reduce the exhaust air flow of our new bigger and better flowed exhaust. Well at some point it will, if we bear in mind that there are other more open stock honda catalysts (S2000 typeR etc). Still is it worth paying 200-300e for getting an aftermarket one?
Furthermore too many prefer to install a test pipe in the place of the stock catalyst, so as to be legit. I wouldn't propose that as it is against the law and secondly we breath all the time the harmful gases.
After all we all need a bit of backpressure that our catalyst can deliver.

This is the general frame of this topic.
In a while i am going to show some economical high flow catalysts from various sources.

I was actually suprised of the dimensions of a cat from a high performance Honda engine, the B16B in this case. Since I got that engine as well in another Civic I also got an (emptied out) OEM cat for it. Despite the bigger 2.5 inch flange on those cats, the inner diameter before entering to the catalyst material is the same small venturi as for a stock D14 cat.

Only real difference is in the length of the catalyst material, for the B16B it is about 20-30% shorter. So the resistance of such a cat will be lower, though the difference between them will be very small.

For that car I am actually getting a racing cat now, curious how it will look. But that could also be used for our typical D14 engines.

For what I noticed from my D14 is that having a cat or not makes a huge difference. Approximatly 3-5 hp over the entire range. I expected only a gain at the high revs when using an emptied cat, but the result showed gaines over the entire range. Probably some resonation/reflection effects as well in there... guessing.

wow! I would expect otherwise to tell you the truth. I was based on the assumptions that a d14 without mid section muffler would lose throughout the powerband. I have heard many complaints from d14 owners when removed their mid box.

I tired my catalyst and noticed considerable gains, the engine respond faster, and i gain more power on low rpm's.

Did you use any test pipe instead? It's tempting but i wouldn't dare it.
Does the exhaust sound change?

saxophonias wrote:Did you use any test pipe instead? It's tempting but i wouldn't dare it.
Does the exhaust sound change?

I replace with a home-made test pipe. the sound looks the same, almost no changes.

And how about the MOT?
Does it pass without the catalyst?
Cheers

My B16B has had a testpipe as well for a while. It was silent! There is a OEM EK9 muffler at the aft, that takes out all the noise. Seems like I could virtually do anything before the muffler what I wanted and it does not change sound.

MOT big fail right now... waiting for the racing cat, I actually have to pick up dragging with the D14A3 now hehe since my B16B is not allowed on the strip without MOT. Over here CO should be 0.5% max, it is barely under 0.5% at idle and it is far over 1% at 3000 rpm which is tested as well here. Are those rules everywere the same? Lowering AFR mixture fixes CO, but then oxygen levels are too high and again fail...

MOT, is IPO? obligatory periodical inspection ?

i don't no the values over here, but some cars have passed without catalytic converter.

but i will mount my when i goes to the IPO.

i'll upload my emission card numbers with the sebring cat i have. It passes emissions for 3 years now.
Speaking of catalysts i think this is a good option



SMS-P is the name. Very sophisticated company that makes some of the most effective headers.
http://sms-products.com/Converters.html
Their catalysts are very well priced too.