MOT - Removing Primary Cats while retaining Secondary

[CoralNova]

Greetings everyone,

Many people have opted to remove the secondary cat but have kept the primary in and passed the MOT. Is there a way to eliminate the primary cats while retaining the secondary ones, such using long tube headers? I'm curious to hear about your configuration. My vehicle's emissions have been fine.

Hopefully someone has already done this on their W211 AMG.

Many thanks

[RumbleRex]

If you plan on removing the primary cats and replacing them with LTHs and 200 cel sports cats, you'll probably have to code out the O2 sensors.
In addition, you increase the likelihood of a MOT failure—perhaps not immediately, but in the future when regulations change.

My E55's secondary cats were recently swapped out for an x-pipe.
Obtaining a set of C63 M156 back boxes will allow you to fully unlock the vehicle.
The only part that needs to be trimmed and rewelded to suit the E55 are the hangers.

[CoralNova]

Much obliged. I am at the age where I can't stand drone very much anymore, so I'm keeping the resonator even though I was looking at c63 backboxes.

[MrTinkerFix]

Gold is the colour of choice for C63 m156 mufflers (backboxes). They are also very expensive when used.

[EchoTrail]

No matter how well it passes the emissions test, removing either cat would technically result in a MOT failure because it is against the rules to remove or alter any factory-fit emissions equipment. Before you remark, "Well, mine passed without secondary," I'll respond: that's fine; we all know it happens sometimes, but it shouldn't. Both of my local test guys have been through mystery shop style inspections this year. One of them had a hollow DPF, which he found, and the other had an EGR that was missing (not programmed out). Now that he's doing so well on his tests, things will only become worse. Adblue deleters and kitten removers, take note: the Ministry will be pursuing you shortly, if not this year or even next.😄

[CoralNova]

I see your point. Earlier today, I stopped into a nearby MOT station. It turns out that VOSA is releasing new emissions testing devices that connect to the OBD2 port in addition to the tail pipe emissions output measuring device. According to the tester, it records the engine temperature, revs, and other data from the car under test. Therefore, it may be worthwhile to keep all the cats for the time being.

[CoralNova]

I remember hearing Olly's a few years ago; it sounded normal until he pressed the gas pedal to the floor.

[WordSnoop]

Basically, it's a game of cat and mouse. With a massive underground economy, the authorities are frantically trying to catch up. However, the trade in unlawful modifications will persist so long as there are individuals ready to purchase and others wanting to sell.

[WordSnoop]

I'll give you an example:

https://themotorbikeforum.co.uk/topic/50868-aftermarket-exhaust-mot/

[WordSnoop]

I upgraded the exhaust system on my SV650. The initial aim was to fit it and then remove it for each MOT.

You get what I mean; well, riding a bike makes things simpler, but still. Anything is possible when one is determined.