Would check engine light turn on because of a 200 cell catalyst?
Would this work without a remap/tune?
Is it necessary to change the downpipe also.

The exhaust now is 21,6 (or 55mm) inches diameter (17,7 inches diameter is stock or 45 mm).
The downpipe and the catalyst are stock. It has a free flow (sport) resonator and free flow muffler.

Ford focus 1.0.

It is possible, these cat’s generally only work properly when they are hot, the downstream O2 sensor may need mapping out to prevent the light coming on, or you could fit one of the O2 sensor extension elbows available online. 

Thank you i will keep it in mind before changing the cat (if).

On 7/1/2023 at 1:20 AM, sttwoton said:

It is possible, these cat’s generally only work properly when they are hot, the downstream O2 sensor may need mapping out to prevent the light coming on, or you could fit one of the O2 sensor

Normally it will pass MOT right?

Would performance be decreased on low rpm?

It will pass, as long as the actual emissions are within tolerance, the elbow should make no difference to that, performance will be no different at lower revs. 

Thank you.

Also perhaps it shall decrease the engine's heat.

I doubt that, the only thing the downstream o2 sensor does is analyse the emissions after the cat.

Wouldnt the temperature be decreased because of the better flow?

Possibly, but it would be rather minimal, it would take a bit longer to get the cat up to full operating temperature, I’d suspect. 

Indeed.

I shall consider changing the downpipe also. A bigger dowpipe would be better?

Now is about 2.16 inches (55mm). Would on 2.37 inches (60mm) be better?

2 hours ago, Bol said:

I shall consider changing the downpipe also. A bigger dowpipe would be better?

A larger downpipe isn't always a good thing.  It allows the exhaust gasses to cool down too much within the pipe, which then causes a restriction and stops the gas escaping so quickly.

So without a remap it is better to let it be as it is?

2 minutes ago, Bol said:

So without a remap it is better to let it be as it is?

Generally yes.  Though I haven't seen any direct testing on this engine.

So only the catalyst would be better to be changed (with a 200 cpsi) and rest of the exhaust pipe which is already changed (from 1,77 inches or 45 mm to 2,16 inches or 55 mm).

I wouldn't replace the cat either if you're not going to remap it.

Doesnt the cat restrict it very much?

Only the wastegate was adjusted. 18.8 psi or 1.3 bar is on maximum originally, now it reaches 20.4 psi or 1.43 bar on maximum.

It wont be remapped.

Remap is the best value for money mod you can do with a modern turbo engine.  There aren't any mechanical changes that will give you anywhere near the same increase as a remap.  Remaps are generally safe as well, I can't recommend just winding up the boost on a 1.0 EcoBoost.  Reliability and longevity may now have been compromised.

Cat's aren't very restrictive, the technology has come a long way since they were first fitted in the '90s!  I have had a couple of sports cats myself and wouldn't say they were worth the money.  They can give you a bit more top end but lose some of the low end torque which is far more useful day to day.  I wouldn't have another one.

Thank you i shall consider all options.

Remap didnt go well for this car.