De-Cat, is it worth it?

[Brind]

Loads of people have removed their Cat and fitted a straight through piece instead.
What bhp power gains can be expected on average?

I'm all for more power but since you have to put the Cat back for an MOT is it really worth it, especially since these roadside checks for emissions will become more frequent! rendering alot of people driving illegally I guess?

Cheers, Brind.

[Brind]

Forget it, I read this:


Q: Can I take the cat off my car INSERT INTO post VALUES (de-cat) to improve performance?
A: Removing the cat INSERT INTO post VALUES (Catalytic converter) from any exhaust system will often improve a cars performance due to the increase in exhaust gas flow it allows. You should however consider it seriously before going down this route. There are a few myths that surround the legality of cat removal in the UK and a few things worth noting if you do remove it.

Myths:
a) Removing the cat is illegal.
This is simply not true, you are perfectly entitled to remove the CAT from your car and fit a de-cat INSERT INTO post VALUES (straight through) pipe as long it will still pass the relevant MOT emissions test.
b) If you remove the cat it WILL fail the MOT emissions tests.
Again this may not be the case. The Japanese car industry had far stricter emissions requirements than the UK and cat’s were fitted to home market Japanese cars for a long time prior to them becoming a requirement in the UK. In most cases you can quite easily remove the cat from any Japanese grey import car that was first registered on, or before, 31st July 1995 INSERT INTO post VALUES (M-reg or earlier) and still pass the less stringent UK MOT emissions test. Removing a cat from a more modern car will almost definitely mean failure of the later more stringent emissions limits. It is worth noting that some tuned Evo’s with an aftermarket ECU can pass the later emissions test even with the cat removed.

Please note that in the UK, new roadside emissions testing is being introduced for passenger cars. If your car fails the test and it is found that you have removed the cat then it will be very probable that you will be fined. The fines depend on the part of the country you are in, some councils being stricter than others with even 4 and 5 figure sums being mentioned, with cars being impounded until the fine is paid. You have been warned!
As with any modification, always tell your insurer.

[jaysback]

brind m8.
if u can bring yourself to do it.
remove cat box
take a long bar and a large hammer
place bar down cat box
smack away knowing that every hit is getting u closer to 300 bhp :)
shake all those nasty pieces of cat from boxINSERT INTO post VALUES (this bit is very impotant)
replace empty box
stand back and look at your very standard looking front section of exhuast;)
then when and if you are pulled over the only thing you get is a pink ticket telling you to get the cat fixed and get it stamped at a mot station.
at this point you may need to buy a new cat:mad:
but how many people do you know that have had a emission test done at the side of the road?

away with with the cat, free your exhuasts breathing
liberate your super drager
you know thats what it needs

[Brind]

I asked this over on the MLR site aswell.
I'd love to have the extra performance that the Cat is restricting but not the hassle if I have to play about with it, if I needed too..
I can see your point about beating the crap out of the insides of the Cat but if I do need to have it replaced, I doubt it will be cheap, and I don't think it would be covered by the warranty especially if they found I beat the crap out of the insides. :D

The responces I have got from the MLR is that they reckon they got away with it without having to remove the Cat for an MOT because their cars weren't listed in the MOT test listing thing.. I'm sure that would be even more the case with our rare cars!!!
I guess I could try this and then have the car tested but could end up a few quid and achieve nothing.
My car is a Ralliart model so mine will probably be listed? and the emission figures known.

Thanks pjjohnson for the PM.

[jaysback]

i have access to a test station and the charts and i know for a fact that the vr4 isnt in there.
the closest thing is the v6 sport.
i will get mine on the emissions tester and let you know the results with and without it:D
i'm on earlies next week so should be able to get up there one afternoon.
p.s. did i read somewhere that these have pre cats in the down pipes?
i know when i de-cated my st24 mondeo that it still passed the mot because of them:Ponder:
will let u know

[-LegnumVR4-]

Should get about 10bhp by removing the cat.

[jaysback]

yep thats what i reckond on
10 - 15 bhp

[Brind]

That would be excellent mate if you could.
10 brake is 10 brake more to the 300 if not over that with the other bits. :)

Would I have to get a Cat replacement piece specially for the VR-4 or will any make or model fit as long as it is the right diameter?
The HKS comes straight from the Cat and that is 3 inches in diameter, no idea what the size is before that?? haven't looked, anyone know? and what is a pre Cat if that makes a difference to size?

Would it sound any different without it?

Cheers!, Brind.

[-LegnumVR4-]

If you like you could build a custom extractor like mine. This way u can remove the cat and have better turbo response and even more power. The stock VR-4 extractor is a dog, just have a look at some of these photos:

[-LegnumVR4-]

You can see how the stock extractor isn't very good, the rear turbo has to flow forward through a small dia opening then turn around and flow back towards the muffler. The after market one u see there is better. Here are some more:

[-LegnumVR4-]

This one here has a different design to the other one. This one would flow very well.

[-LegnumVR4-]

Heres a close up of the 2 pipes meeting. It's very tight under there. If you are going to get the pipe made up make sure you get it done by a pro, the guy that did mine did it all wrong putting the rear turbo exit pipe on top of the front one which limits the space between the subframe. The rear pipe can hit the subframe and it will have to be 'adjusted' which harms flow. The font turbo pipe has to be as close the diff as possible (like this photo) to allow enough room for the rear turbo pipe. If the guy says he can't do this design then go else where, I know i payed the price for mine as it doesn't flow as well as it should.


Notes:
Theses photos are not of my extractor. Theses are the aftermarket Japanese designs.

If you remove the cat the exhaust will become louder. Putting in a resinator will fix that.

[Brind]

That's my "will any de cat pipe fit assuming it's the same diameter" question answered.
looks very good and purposeful.
I bet it will be very expensive to have made, especially over here.

Do you know what kind of gains you got from your setup? or have you only done a combined test with all the mods fitted?

[Pescha]

Wow! Great pictures -legnumVR4- :thumb:

Hehe Thanks for sharing!

Cheers,
Pescha!

[-LegnumVR4-]

I did the test when i had my Fujitsubo already installed. The car felt like it flowed a lot easier. The pipe will give your turbos better response (spin up quicker); you'll gain a bit more psi which will give the car a bit more power.

Really the car felt a bit flat from stock, once you install the new pipe it just flows up to redline.

[jaysback]

yep!
those pipes look the best
still not been up to the test center yet
will keep u posted