Wanting to change my cat out for an 200 cell free flowing item. As far as I can see, the cheapest direct replacement option would be about £475.

I'm thinking about buying a decat pipe from TMC or Ragazzon and then putting a 200 cell cat under the car just in front of my middle silencer. This could be done for about £300 or less. Any disadvantages to this set up vs cat in downpipe? Car has a 2.25" cat back system on already.


TIA


Ben

Ben D said:

Wanting to change my cat out for an 200 cell free flowing item. As far as I can see, the cheapest direct replacement option would be about £475.
I'm thinking about buying a decat pipe from TMC or Ragazzon and then putting a 200 cell cat under the car just in front of my middle silencer. This could be done for about £300 or less. Any disadvantages to this set up vs cat in downpipe? Car has a 2.25" cat back system on already.

TIA
Ben

Click to expand...

Checking that the cat is fitted is now part of the MOT. If you fit one that looks different from the factory fit you might have trouble at the MOT.

Robert G8RPI.

Standard cat in the downpipe off the turbo?

Moving it under the car as you have stated would be a advantage as it will reduce temperatures at the turbo.

(As you know i have a Corsa 1.6 as well as the punto with precat in the downpipe and main cat under the car - the temperature issue is one reason why all of us remove the precat (plus it helps spool quicker)).

BTW I'd bee interested to know how much you pay for a custom section with sports cat... my Corsa is still running the the standard main cat but everything else stainless and i want it changed for a sports cat. Was going to try Powerflow @ Turriff Tyres to make it up...

g8rpi said:

Checking that the cat is fitted is now part of the MOT. If you fit one that looks different from the factory fit you might have trouble at the MOT.

Robert G8RPI.

Click to expand...

Yes, theoretically true.

He stays near me though and there are plenty of sympathetic garages nearby so he should be ok...i've not had issue with my Corsa and its one cat down compared to standard anyway.

Grande Puntos aren't exactly common up this way anyway so chances of the MOT tester knowing the standard exhaust system setup are slim.

Yeah,

Cat in downpipe but only one of them.

The only concern I have regarding MOT would be the cat not getting hot enough to pass but I'd wrap downpipe to keep heat out of engine bay and in exhaust. Surely tester would see it under car? Only has to be visible and pass emissions, no?

Turriff did my system, I'm happy with it although I'm not sure they like doing anything too complex. I went in for a cat back and they wanted to cut downstream of flexi and run from there back, they were worried about getting the shape around the sump and took some convincing. Welding is spot on and system seems well made I'd not have any hesitation getting them to weld a cat in underneath. Only slight issue was them not changing rubbers, system dropped a little and I had to sort it myself to take it off my forge braces. They wouldn't entertain touching the downpipe to change the cat.

I'd be fitting downpipe myself taking cat up there and getting them to put it in.

Main question was regarding any potential negative performance or operation issues from having cat underneath as opposed to in downpipe?

Cheers

Ben

I don't think temperature would be a problem as plenty cars have cats in that position.

The question mark is more over the 200 cell cat - they all vary in quality so while it should pass the MOT some do and some don't as they are close to the borderline on how much gas they can process - e.g there have been a lot of people who bought Cobra sports cats on the Corsa forums and found their 200 cell cats don't always pass!. They're about £360 to buy as well!

For this reason most people just decat and swap the cat back at MOT time.

Have you thought about doing that?

That way you get more performance, it costs you less and no worry of the car not passing the MOT. I mean how long would it take to swap it over each year...maybe 2 hours worst case?

Depends how moral/leal you want to be for each other day in the year.

Ben D said:

Yeah,

Cat in downpipe but only one of them.

The only concern I have regarding MOT would be the cat not getting hot enough to pass but I'd wrap downpipe to keep heat out of engine bay and in exhaust. Surely tester would see it under car? Only has to be visible and pass emissions, no?

<SNIP>

Cheers

Ben

Click to expand...

Current UK MOT emissions test does not check operation of the catalyst, just CO and hydrocarbons. That is why they brought in the visual check.

Robert G8RPI.

Decat arrived


Just need to decide on which cat and find a loom extender for the sensor.

Decat fitted today, just waiting for magnaflow cat to turn up so I can get it welded in under the car. Got a spacer in the rear O2 sensor and no EML so far. Not too bothered if it does come on as it's not going too far before I get the cat on, you can smell the difference in exhaust and it's obnoxiously loud.

Decat was from Friedrich Motorsport in Germany sold as for a 500 Abarth, outlet of 60mm ID and has all heatshield brackets. Fits perfectly, excellent quality and less than £180 delivered.

Only thing needing work was the original lower bracket, this needed a run over the grinder due to increased diameter of outlet compared to original cat.

Cheers

Ben

Cat now in place and extended sensor in just behind it. So far so good, no EML and no codes present and car smells like it did with OE cat. Is there any way to check the efficiency and likelihood of MOT pass through MES?

Under bonnet and intake temperature is definitely down and temps recover much faster after a period of idle or town driving.

Cheers

Ben

Yes, there is a pretty good way:
In MES you need to graph both O2 sensors:
-make sure the cat is fully up to temperature like a good 30 minute highway
-the graph of the second O2 should basically vary only a small bit while the first one should vary constantly




You should know that catalytic converter inefficiency errors do not show up right away... after a reset it could take anywhere between 150-400 km to come up.
I think the Ecu takes into account how much time the car drives at operating temperatures, because if you only have short journeys, you will never reach operating temperature for the CAT, but it will not throw an error. (a good CAT and a bad CAT will behave the same)
But if you drive with a bad CAT for a longer trip~200km it will throw the error pretty early on.

Thanks mate, got about 180 miles to go tomorrow so hopefully will see then if I get a light. Torque showed catalyst incomplete in the monitoring box today until I'd done about 40 miles then showed as complete. I presume this was cat getting up to temp or new sensor settling in as prior to fitting, I had a faker / cheater and sensor in standard location for a while.

Sensor 1 was reading as normal, sensor 2 was definitely moving less so roughly looks ok. Will get MES on the go in next week or so.

Cheers

Ben

How long did it take to have the cat welded in?

u33db said:

How long did it take to have the cat welded in?

Click to expand...

Approx 60-90 mins along with boss which I got them to plug. I fitted the sensor myself at home as I needed a route for the cable.

u33db said:

How long did it take to have the cat welded in?

Click to expand...

Decent length drive today, still no EML

Once warmed up graph of the O2 sensors at idle, this looking OK?


Cheers

Ben

it does seem to work.. a little.. but something isn't right... the second O2 is siting around 0.7v... ideally it should average around 0.45v.
0.7 means it's running a bit rich... i am really curious if it will pass a MOT emissions test.

Ben D said:

Approx 60-90 mins along with boss which I got them to plug. I fitted the sensor myself at home as I needed a route for the cable.

Click to expand...

Thats not bad.

I think i'll be going up to them at some point soon to weld a cat into the stainless decat pipe i bought 2 years ago...i'm still running the standard cat on the Corsa and after 10 years its in a bit of a state!

I've given up doing anything more to the Punto...i've stuck some different springs back on it so its more like standard ride height as i'm sick of spending my weekends working on it, and sick of scraping the speed humps! I've honestly had the suspension off 5 times in the last months whcih is a bit of a joke.

MOT today with new 200 cell cat fitted. Required a little warming up but went through fine

Emissions with standard cat from last year for comparison