Remove Cat? the law?Gains, Losses?

[ghostbuster]

Please excuse my ignorance but many people talk of it but what is the law regarding cat converters and is there much to be gained and/or lost by removing?

 

Regards,

Mike.

[red_zebra]

Are we talking N/A or TT?

 

If TT have a look here for gains

http://www.mkivsupra.net/vbb/showthread.php?94705-BPU-(Basic-Performance-Upgrade)

[Pete]

Depends how friendly your MOT station is.

If it's an import you may be able to convince them just to go off the emissions as they won't have an official vehicle type on their computer.

That's so long as your emissions are under of course.

[Guest Roger NE]

There is no legal requirement to have any Cats fitted to a car at all . . . (although manufacturers have to fit them by law, there is nothing to stop you removing them)

 

It's just that your car needs to pass the appropriate Emissions test - there are different limits of emissions, depending on the age of the car or engine (whichever is the oldest)

 

For example, the pre 1993 test is normally referred to as a Non-Cat test . . the post 1993 one is referred to as a Cat Test

 

However, my car with the Cat removed EASILY passed the Cat test.

 

If your car is in the MOT Emissions database, there will be particular Limits for that vehicle. (although I expect they would be similar to the default figures below for Supras)

 

But if it's an Import (not normally sold in the UK), it has to pass the Default figures.

 

For a 1993 to 2005 car the default "Cat Test" requires less than 0.3% CO, Hydrocarbons less than 200 ppm, and a Lambda of between 0.97 and 1.03

 

So to re-iterate, as long as your emissions are below those figures it will PASS - regardless of whether it has a Cat fitted or not.

 

Having said all this, it seems a lot of MOT Testers DON'T understand all this - I know some people (who've had problems) have printed out the VOSA Guidelines to show them !!

Edited February 2, 2014 by Roger NE (see edit history)

[supraGZaerotop]

interesting

[Guest Budz86]

Everything that Rog has said is true; well put mate. Although I remember reading that VOSA want to make the cat mandatory, so if it had one at manufacturer, it would need one to get the MOT. Solution is either refit at test time or get one modified with a decat pipe in the middle.

 

Not sure if they ever got this approved though, I don't think it was an 'immediate effect' thing anyway

[Guest Roger NE]

I've never seen anything to say the Law has changed, ie that you HAVE to have a Cat fitted.

 

In terms of gains . . . well removing the Cats should give you 10 - 15 bhp extra on an N/A

 

On a Turbo engine, you have to be careful, as the Cats give quite a restriction, which limits the amount the Turbos can boost - simply removing them although giving you increased power is likely to damage your turbocharger, so you normally then need to fit an exhaust restrictor ring (but gather this is well documented on this site)

[garethr]

Everything you need to know is here and here.

[Guest Roger NE]

That's interesting to be able to look up ACTUAL required figured for different cars in the Annex.

 

However, I see that for Mk4 Supras (only TT listed, as others are imports) the figures are the same as the default "Cat Test" ones I posted earlier . . . ie less than 0.3% CO, Hydrocarbons less than 200 ppm, and a Lambda of between 0.97 and 1.03 (that is all at Fast Idle = 25000 rpm) . . . at normal idle speed they only check the CO, which must be less than 0.5%.

 

Well, even Mk3 Supras are WAY better than that with all the Cats removed ! So you shouldn't have any problems passing with no Cats (unless you have a fuelling error)

[ghostbuster]

Great answers everyone. We learn a little every day. Thanks.