Our thoughts on Primary Cat Removal on V12 Engines

In November we exhibited at the Classic Car Show at the NEC in Birmingham. It’s an annual event for us and we love meeting clients and talking about cars. This year we were surprised about the number of people asking us about our lack of YouTube content and what our thoughts were about Primary Catalyst Converter removal or delete, on the V12 engines. It’s December, we have time so here we go.

Firstly, why would you want to remove your Cats?

They don’t have any manufacturing issues that we are aware of and Aston have never issued a recall for them. If you are looking for more performance and you want to modify your car it will cost thousands of pounds, money you won’t get back as you know but it’s your car and who am I to say? Your engine management will have to be re written to cope with the change and this may mean deletion of the Engine warning light full stop, this means your engine cannot warn you if it has a problem, a misfire for example and if that is the case you may not know about it until you have major damage because your exhaust sensors can’t tell you about it. This will also void any warranty you had and prevent you from selling back to the main dealer network and most others as warranty companies will not pay out on modified cars, remember they are always looking for an excuse.

The most common reason we hear is that owners are scared their engine will have a miss fire and damage the Cats. Once damaged the fragments will be sucked back into the engine and cause untold damage.

Our opinion

We can only comment on our experiences and opinions. Our response is this. We have been buying and selling Aston Martins since the late 1990’s. Since 2004  We have bought and sold something in the region of 3,500 to 4,000 used Aston Martins in that time. How many of those cars that we sold, warranted, bought back and sold again have ever had an issue with a Catalytic Converter? ZERO! Not one car.

If you are being advised you should carry out this procedure please make sure it’s the right choice for you and your car and your reasons are well justified. Is it possible? Well anything is possible. Is it probable? We think it’s highly unlikely and as we have said of all the Aston Martins we have dealt with over the years it’s just never happened to us at all ever and Aston Martin don’t seem to be worried about it either or you would have a letter about it I’m sure.

Originality is key to the value of your car especially as it gets older and reaches for Classic Car status. Your Aston needs to be the best. The most original well cared for car on the market. History tells us that the best cars are presented with Certificates of Authenticity and Originality around the world by different manufacturers and yours will be no exception. Modified cars are generally frowned upon in the used market and the cost is a factor. Is there an environmental issue here too dare I ask? A brave question given the V12 engine. And don’t forget the value of your used cats. The precious metals are well sought after and will fetch a lot of money. Whilst writing this and out of interest a local recycling center would offer me £500 for one manifold containing two cats. A profitable business in itself clearly.

We hope you find this short article helpful in your decisions and knowledge about your Aston.

Here is a short clip on Youtube:

UPDATE! 9th January We have been contacted by the DVSA!

Our latest video clip:

We wrote this post in December and have been inundated with consumers asking about our thoughts. We were tagged by a client and the DVSA have got in touch with us today 9th January. Their response is important as they have just won a court case with another about to be made public. Following that they will begin to enforce their success. Read about it below here: https://www.am-online.com/news/aftersales/2023/11/28/garage-fined-by-dvsa-for-fitting-illegal-aftermarket-parts

The following is our interpretation for their stance on the law regarding exhaust and or ECU modifications. I have included the official text below.

If a manufacturer builds a car to a certain specification that is governed by law, that should not be altered or adjusted. Case in point if you choose to remove the catalytic converters from your engine you are breaking the law because you are adjusting the carbon output and specification.  If you adjust the ECU to help with the running of the engine and or to help with passing an MOT again this is contrary to the law. This is the case for any catalytic converter on your engine. If you have made these modifications to your engine you cannot sell the car without fully disclosing this to the buyer nor can they sell the car on. Whilst driving the car on public roads this is an offence.

The Law

  1. s76 Road Traffic Act 1988

Fitting and supply of defective or unsuitable vehicle parts.

(1)       If any person—

(a) fits a vehicle part to a vehicle, or

(b) causes or permits a vehicle part to be fitted to a vehicle,

in such circumstances that the use of the vehicle on a road would, by reason of that part being fitted to the vehicle involve a danger of injury to any person or, constitute a contravention of or failure to comply with any of the construction and use requirements, he is guilty of an offence.

(2)       A person shall not be convicted of an offence under subsection (1) above if he proves—

(a) that the vehicle to which the part was fitted was to be exported from Great Britain, or

(b) that he had reasonable cause to believe that that vehicle—

(i) would not be used on a road in Great Britain, or

(ii) that it would not be so used until it had been put into a condition in

which its use on a road] would not constitute a contravention of or a failure to comply with any of the construction and use requirements and would not involve a danger of injury to any person.

  1. The Road Vehicles (Construction and Use) Regulations 1986.

Silencers Regulation 54.

1) Every vehicle propelled by an internal combustion engine shall be fitted with an exhaust system including a silencer and the exhaust gases from the engine shall not escape into the atmosphere without first passing through the silencer.

(2) Every exhaust system and silencer shall be maintained in good and efficient working order and shall not be altered so as to increase the noise made by the escape of exhaust gases.

(3) Instead of complying with paragraph (1) a vehicle may comply with Community Directive 77/212, 81/334, 84/372 or 84/424………

  1. The Road Traffic Offenders Act 1988 schedule 2

provides that this type of offending is punishable on summary conviction, to a fine not exceeding level 5 on the standard scale (unlimited for offences committed after 13 March 2015)


In response to your question regarding removing vehicle parts:

Under the Road Vehicles (Construction and Use) Regulations (Regulations 61(7) and 61A(3)) and the Road Traffic Act 1988 (Section 42) it is an offence to use on a road a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet. Under Section 42 of the Road Traffic Act 1988 it is also an offence to cause or permit a vehicle to be used on a road that is non-compliant with legal emission requirements.

Furthermore, under the Road Traffic Act 1988 (Section 75) it is an offence to alter a vehicle in such a way that the use of the vehicle on a road would be unlawful. A person altering the vehicle (if they knew or believed that the vehicle would be used on the road) could be found guilty of an offence under the Act.

Further information can be found on-line at:  https://www.gov.uk/

or Sophia Mir at the DVSA https://www.gov.uk/contact-dvsa

This information starts a whole series of different conversations and raises many questions. If you have removed any of your cat converters hopefully you have retained the originals. We are always on the end of the phone to help if need be.

If you wish to seek legal advice and an expert opinion on your position we recommend speaking to Mr Hojol Uddin of JMW Solicitors. Please e mail him: hojol.uddin@jmw.co.uk