CGA3DE Decat

Hi guys.

I have a 2001 1.4 and I have rummaged through the forums without a clear understanding of how this is done? Especially for my motor. Most of the links in the threads about decats are dead too. :cautious:
I simply cut the cat out of my previous 1.4 polo and got a straight pipe welded in and it made the world of difference to the throttle response and added a cheaky little sound. This was in South Africa so no one was worried about the polar bears. How much use is a 18yr old cat anyways with 100k miles on it. ;)

My main questions are:
How many cats does it have? Looks like a middle one and one out the manifold?
How do I pass MOT, I am assuming these need to bolt on and off or at least look like they are still in tact ?
Is the O2 sensor affected ?

Thanks in advance and apologies if there is a thread about decat'ing my motor already.
CGA3DE only has 1 cat. And its in the manifold. So you need a new manifold. You need to swap the manifold back to one with a cat for MOT. And yes the o2 sensor is affected because the cga3de has 2 sensors 1 in front and 1 after the cat. You will also get a check engine light with a cat failure code.
Thanks for this.

I cant seem to find anyone who sells these decat manifolds.

Ideally the plan would be to get a manifold with a cat look-a-like or the the cat cut out the manifold so as to pass MOT?

This is a very ghetto solution but would it work and would the O2 sensor still be fine ?
Gizfab sells manifolds but they dont have a cat. You can always weld one in another part of the exhaust. Or if you get a aftermarket manifold that connects to the stock middle section you can also grab the 2nd cat and middle section from a 1.3 because that one has 2 cats and the lenght of the middle section combined with the 2nd cat is the same as the 1.4 middle section.

The 2nd o2 sensor will give an error if there is no cat. There are o2 fakers that you can screw onto the 2nd o2 sensor. They contain a really small cat so that it doesnt give an error.
From what I have read though, you are very unlikely to pass an MOT with just the 2nd cat from a 1.3.

Keeping the 1st mani cat and losing the 2nd can get through but not vice versa.
If these old Cats don't restrict flow that much then I am going to rather leave it. Thanks either ways. If it ain't broke and all....
If these old Cats don't restrict flow that much then I am going to rather leave it. Thanks either ways. If it ain't broke and all....
they look like honeycomb inside, eventually it caves in starting in the middle and wears a hole, if it's big enough you'll fail your MOT on nitrogen

Even 2nd hand or old ones are worth a bit of money (to replace it with a working one) because they contain platinum

The thing is, while a muffler or a resonator is basically a pipe the same diamater as the rest of your exhaust, with tiny little holes in it like silencer on a gun, with sound proofing or damping material wrapped around the holes, and then another pipe surrounding it so stop the gas leaking, a catalytic converter bows outwards. So it's a pipe, which widens to around double or triple the width of the standard exhaust, with honeycomb shapes, which then at the other end tapers back down to the width of the pipe.

While it does increase backflow slightly to have anything interferring with the flow, and straight piping does reduce backflow. Firstly you do need some backflow within an engine (I might be wrong on the reason but I think it has to do with valve float or something similar within the engine and cams), and the other point is that the custom manifold piping has to be designed in a certain way to produce some backflow to work with the straight piping. It's a complicated thing. I have a buddy who races 50cc classics and you wouldn't believe the work that goes into these custom exhausts to squeeze every last bit of power out of this tiny engine.
Thanks for this.

I think I have been basing this whole thing off my previous car that had a tiny cat. So that may have been where the restriction was but the improvement was minimal.

Never Knew there was an emissions test with MOT, thought it was just a quick look to make sure there was something that resembled a cat in the exhaust system.

With MOT and the large diameter of the cat taken into consideration I think the best thing to do is to just leave it as is, its not like its a race car or anything ;) Also have MOT coming up at the end of the year and I am already spotting things that I am sure will be a fail ( torn drivers seatbelt) that I am putting time and effort towards.

I had back pressure issue with my Single Cylinder 4- Stroke Honda Motorbike that resulted in me putting the stock pipe back on just to regain some driverablity, pretty sure you are on to something with the valve float, it would not be the first time I have heard it brought up.

Do we know roughly how long these cats are meant to last ? She's a 2001 with 100k miles on the clock. I don't really want to start looking for some platinum parts for my car right now>

Thanks alot for this, you guys have stopped me making a rather stupid racer boy decision.
I think they're designed to last the life of the car, but can be poisoned by certain things (like putting diesel in a petrol for example) or age can cause them to deteriorate

the MOT test is a probe in the end of the exhaust, you might have seen them do it. Sometimes they print a second page that shows your emissions. As far as I know they don't actually examine your exhaust at all, although if it's blowing then maybe that's a fail.

and if you're into your bikes you'll like this:

This is the sort of thing they were building when I visited my mate's garage. They make them out of strips of metal welded together with the flanges machined on a lathe, the designs for the 50cc ones looked like vuvuzelas on the end :ROFLMAO: they would spend hours putting all sorts of weird bends in them for a gain of 1/3rd of a horsepower just to get that little edge over the other teams
When the car went for alignment I had a peak underneath and it seemed in pretty good nick ( besides the the rear axle being a bit rusty)

My MOT is only coming up at the end of the year and I'm already looking for things that it will fail on.

Those welds are almost pornographic.

I love how so much work and research goes into a 50cc