de-cat down pipe

usely by putting a decent pipe in the exhaust flows better /ie better responce and cleaner breathing engine ,, until mot arrives and it will need poping back in ,,,,

powernut said:

........ until mot arrives and it will need poping back in ,,,,

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not true for a diesel. A derv will pass without the cat installed.

I have a decat down pipe and it is a great mod good gains and will still pass a MOT on derv.

i have had a decat on my tdi for 2 MOT's now and no problem

ibizadoyle said:

so it doesnt put strain on the turbo then?

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Should'nt do, as its letting the gasses flow out quicker

It'll ease pressure on the turbo, less pressure on the output side to try and slow it down by exhaust gasses. Full straight through exhaust is what id be going for get rid of that back box.

is it simple enough to make your own decat? ie. same as with mufflerectomy?
Just cut it out and weld a straight piece in?

Also maybe planning a completly custom exhaust, (if work let me use the ramps haha)
complelty stainless steel, dect, deleted silencer, and was thinking maybe 3" bore mandrel bent pipe from the turbo straight to the back?

Sound any good or is the bore to big, will I loose all backpressure, as im sure a small amount is required, or will it do the trick?

thanks for elaborating...

Back pressure is all provided by the turbo itself, you need no back pressure what so ever after the turbo.

so why cant you just chop the cat out and weld another bit of pipe in?

rscott4563 said:

Back pressure is all provided by the turbo itself, you need no back pressure what so ever after the turbo.

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THIS is the key statement when it comes to exhaust mods on a derv. NO need for back pressure to be provided by the Zorst at all. The freer flowing the better, which is why mine is 2.5" right through, to side exit to keep short. Just one silencer as it was a bit noisy, but even that is a straight through on full power.

Cat is really just there for emissions and unless you're a greenpeace hippy activist type, you really want to remove it asap.

so you can just chop it and weld in a piece of pipe?

brightsideteeem said:

so you can just chop it and weld in a piece of pipe?

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Fooks sake YES!!!!!!!!!!!!!!!!!!!!!!!!

Well why ddint someone just say yeah. I got it about the backpressure, thought ther'd be another reason why you couldnt (ie. where it is).

And it would be more helpful if instead of just putting a snidey comment like "no.." and not elaborating on why, then there'd be no confusion.

TBH when the thread has elaborated to the fact that removing the cat doesn't effect back pressure and that many peeps have had there's removed with no problems, kinda make you think, hell yes I can just cut it out and fit a pipe in.

well that was my thoughts, btw I wasnt being like, funny with you. Only got confused because someone said no and i was like "wtf why not??"

Also maybe planning a completly custom exhaust, if work let me use the ramps, complelty stainless steel, dect, deleted silencer, and was thinking maybe 3" bore mandrel bent pipe from the turbo straight to the back? Do you think the bore is too big, too much like overkill, as I now know you dont need backpressure, or would 2.5" do the trick like devonutopia's fabia?

My car is a 110 ASV, non PD engine by the way, if thats any use lol

brightsideteeem said:

My car is a 110 ASV, non PD engine by the way, if thats any use lol

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As long as it runs on the foul smelling oil, it doesn't matter.

Only the newer DPF equipped 2 litre diesels struggle to get around the decat issue more.