I’m going to start the process of sorting a secondary CAT delete for my S1.

I just need more noise.

Has anyone done this?

I’m hoping it doesn’t set off a light on the dash for emission readings.

I’ve performed a secondary CAT delete on a V12 car I have with no adverse effects

Is there room for a cat bypass.

Can you get access to details of the ecu data management?
I have a Rover Gems Plus8. The system monitors exhaust and has two O2 sensors for each cat. Upstream and downstream
Basically The upstream measures emissions and downstream post cat to indicate cat performance/ failure. It has heated sensors and monitors the heating too. I did have a post cat heater fault trigger the MIL but cleaning contacts sorted it. I have an Autel Maxiscan OBD unit that can delete minor detected faults and also check running data. It covers O2 sensors amongst the many other parameters.
Some systems can be “fooled” to compensate, I think a lot of the plug in chip devices do this by modifying signals.
There should be some aero experts who can-advise.
One point to watch is MOT. If you remove a cat then it is an auto fail just from a visual. Maybe a cat divert would be better? Some cars have that as a standard. Putting the car into a spirts mode triggers a divert valve or similar.

Hi Viper. I had sports cats on mine and removed them a few years ago because the nuts were nearly rusted through and gave them a coat of zinc oxide paint. The boy in me couldnt resist staring the engine it sounded bonkers quite frankly and the ecu light came on immediately. After re assembly and the cats fitted the light stayed on and the car started revving on its own not hunting but revving, switched off started again the revving stopped but the light stayed on. Someone might have been the factory told me to dissconnect the battery leave it for a while then touch the battery with the positive terminal a few times and to my amazement the light went out .Back on topic I think you might have issues if you remove the cats but in fairness my exhaust system wasn't connected up when i started the engine. Stupid question have you got a sports exhaust fitted some people think if you have a quad exhaust its a sports exhaust this is not the case on an Aero.

I have a switchable silencer on my Plus 8, but have kept the cats. Sounds epic under hard acceleration!

I thought there were a couple of options ?

Sidepipes or normal
Sports cats or normal.

You could have the sports cats with either exhaust design?

I was not aware there were secondary cats but the Coupe has the sidepipes and there would be no room to fit secondary's ?

Thanks guys

Great advice here.

One cat each side might just work enough but my exhaust man is suggesting if he fits the lambda at a 45deg angle or moves it further out of the exhaust air stream then it will read a weaker mixture.

Not too worried about a light although a pain. Just didn’t want it to try and alter mixtures to compensate but from what I’m hearing it only throws a light.

I have. Librands system with the under sill silencers effectively piped through so just running the cats and rear in pipe resonators to silence it. It’s still fall to quiet.

I might take a cat off and get a pipe made.

Will report back.

I did the same on my V8 Vantage, couldn't be happier with the results (but there I have an exhaust with the valve)
I was not aware that the Aero had a secondary one (but noisy enough wiht the side pipes).
Does it have some sensor on the sec kat? EarlierVantage had it.

Watching this with interest, seems mad having 4 standard cats on these, I would love to delete 2 and replace the remaining with sports versions..

Does sombody have a pic of where the second one is?

This was my full rear exahust.
https://www.facebook.com/photo/?fbid=266121430240087&set=a.266120833573480

And no space for the secondary one with the side exhausts
https://www.facebook.com/photo/?fbid=266121566906740&set=a.266120833573480

Just before that there is the main kat, this
https://www.facebook.com/photo/?fbid=499111936941034&set=a.499111573607737

I have a V12 Vantage. Remote switch for the flaps too. Superb noice

Secondary cat is before the side long silencer.

There’s a lambda there pre 1st and post 2nd

I wonder if the BMW cars using this engine had 4 cats as well? Seems a curious setup with two back to back either bank.

Fairly standard on a big engine

Viper, given that squeezing 4 gallons (AM V12) into a thimble (V8 engine bay) along with all it's additional cooling etc is the 4 cat solution not more related to packaging? 4 little un's instead of 2 bigger un's?

Hence the sensor being over the pair of them?

Meant as a question as much as anything else.

Alistair.
You could have a point but I’m not aware of any large lumpy V engine with just one per side. Could be wrong of course.

Sensors are always pre and post. Would be pointless putting a sensor after the first thought that’s effectively what I have on the AM now.

I’m trying to build up enthusiasm to take the aero apart and send the cats off atm.

I need to have a really bored few days I think

Just watch the news, that will do it.

Have you bored yourself yet? Please say yes

No not yet. Went into the garage with goof intent and couldn’t be arsed. I’ll get there

Hahaha

I don't know how emissions inspections work in the UK, but here in the US removing catalytic converters is verboten. Tampering with any of the required emissions equipment subjects the owner to fines and suspension of the vehicle's registration. Companies that supply emissions work-arounds are receiving big fines Like this...

Over here as long as it passes the MOT every year (inspection) then you’re fine.
Most of these cars will pass that emissions check with one cat and some heat - so make sure you drive hard on the way to the test and get the cat hot 😁

I think now though if an MOT tester sees that a CAT has been deleted then it’s a fail

I am aware of people who de-cat new cars as they have the three year period (soon to be four if you follow the gov's recent crap review of the MoT process) and enjoy the additional fun. Given the rules around car exhaust volume now in place it needs something to provide aural enjoyment. How the Aero dual sidepipes ever pass is a mystery to me.

Once into MoT they are getting very fussy now. A couple of GTR owners I speak to have a section of the exhaust made up where the cat has been removed. Each year prior to the MoT they slip the cat back in and take the test. Once approved it comes back off and the blank is fitted again. The engine map is selected for no CAT and the thing sounds just naughty. One did try and get buy with a hot engine and tight engine map but it was failed.

Everyone needs a friendly MOT man

The replacement bypass pipe is a good option if you don't have a friendly tester, or 4 sports cats I guess but that seems expensive..

I guess they other way round is to just bash out the insides of one and then you don't need any new bits, and visually it looks the same.

I was never a very good mechanic a lifetime ago but here goes. Don't bash the insides out, if you must take the box off cut with a grinder from the middle out so you can see the baffles then access the box and remove the plates carefully when the box is empty weld a plate back to the box. This is best done on the top of the box so when it is re fitted it still looks stock from the underneath.Be aware your engine may run a little leaner and therefore hotter whip your plugs out after a tank full and you should have your answer. Personally if you have sports cats and a sports exhaust I would leave well alone but we all have choices.It will sound good though...

Also if its a stainless exhaust weld back a stainless plate back on unless you did a good job with the grinder so the original might just fit.

I’m not going to cut or bash an existing CAT just in case it needs to go back on.

An MOT tester can’t see anything untoward as it’s all hidden on an aero

Sorry Viper should have read the post more closely I thought Nick was talking about the box not the cat. My cat was clearly visible from under the car well half of it was...,

So have you done it yet..

Nah. I still can’t bring myself to pull it all apart

I will but just not yet

Can't wait to hear it when its done.