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Discussion Starter · #1 ·
I know this has been covered before, but I think I'm going to get a decat. I know it would fail its mot on emmisions but im planning on switching it back for the mot day. Only thing that worries me is being pulled and the old bill checking the emmisions on the spot. has this happened to anyone? worth it or not?
 

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rover_45
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NO! This is a racetrack mod ONLY. You car will produce filthy horrible smog creating emissions inflicted on the rest of us that are far worse than a pre 1992 car. A catalytic converter equipped engine is designed to produce more unburnt hydrocarbons than a non-cat vehicle because the cat needs them to work properly.

It's selfish, illegal and antisocial and if you are caught the police are far more likely to refer the matter for prosecution than they used to. Your insurance will be invalid and they may also prosecute you on this basis.

On a more practical point, your engine is designed to work with a certain amount of exhaust back pressure. Without other changes this mod may damage your engine.
 

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More to the point, it is a waste of your hard earned as you will get no more power for it.

Save your money and the hassle.
 

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Discussion Starter · #4 ·
Not getting into this argument, but it does free up some power and improved responce. You've mentioned some fair points though
 

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It may free up a few more horses but the back pressure required to acheive the correct valve overlap where the exiting exhaust gases create a vacum to help introduce an inlet charge in the chamber would need a tuned pipe to get the best out and most of these decats I have seen are just a simple hollow tube, correct me if im wrong.
 

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cityrover
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plum25 said:
Not getting into this argument, but it does free up some power and improved responce. You've mentioned some fair points though
Its not an argument!! The fact of the matter is it just doesnt do that!!
 

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Discussion Starter · #7 ·
Phil_216sli_Mk3 said:
Its not an argument!! The fact of the matter is it just doesnt do that!!
Err..yeah it does. Why would people get decats and sports cats if the origional cat was good for performance :doh:
 

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cityrover
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plum25 said:
Err..yeah it does. Why would people get decats and sports cats if the origional cat was good for performance :doh:
You have obviously not seen a power chart showing the difference between a k series with a cat and without one. Some cars it makes a gain, others it doesnt, the k series being one that doesnt show any gain.
 

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De-cat and sports cats are a different kettle of fish IMO.Sports cats are generally designed for the exact engine requirement whilst also enhancing power while staying legal.De-cats that ive seen are just a piece of pipe stuck into the exhaust
 

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Discussion Starter · #10 ·
Phil_216sli_Mk3 said:
You have obviously not seen a power chart showing the difference between a k series with a cat and without one. Some cars it makes a gain, others it doesnt, the k series being one that doesnt show any gain.
you obviously haven't driven or been in a 200 with a decat. Combined with other mods it gives the knock on effect resulting in reasonable gains
 

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rover_45
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plum25 said:
you obviously haven't driven or been in a 200 with a decat. Combined with other mods it gives the knock on effect resulting in reasonable gains
Naah! It's just a louder exhaust and you getting high on the unburnt pollutants that's making you think that!:daft: :stir:
 

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cityrover
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plum25 said:
you obviously haven't driven or been in a 200 with a decat. Combined with other mods it gives the knock on effect resulting in reasonable gains
Ive driven a 218is and to be honest with the decat, full stainless cat back system and an enclosed filter up front, i couldnt tell the difference from my pretty much stock 216sli. If you really want to do it then its up to you obviously, just trying to save you some money really.
 

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I've got a de cat on a zs 180. It passed it's mot last month with the de cat in place, when i compared the emissions sheet from the previous mot there is no difference in the figures there exactly the same not even .1 out. Seems that the pre cat is doing it's job well.

When i fitted the de cat the difference was immediatly obvious, it's much free'er revving and theres a nice pop when lifting off in 1st.

I've recently rollerd the car and got 193 bhp @ the fly, thats 18 bhp over standard. The techie said that it climbed all the way to the limiter and didn't level off at all. There are other mods though.

Bmc cda probaly gives about 10 bhp
Piper cat back probaly about 5 bhp
So the de cat gives about 3 bhp

It would probaly be better with a sport cat though, as mentioned the k series is fussy about back pressure. The de cat didn't cost me anything as i fabricated it myself. But when funds allow i'll be replacing it with a sports cat ready for the manifolds.
 

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surely the reason for the de-cat pipe doing nothing on the k-series is because theres another cat on the manifolds... gains can be expected when de-catting and replacing the manifolds?
 

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offkilter said:
surely the reason for the de-cat pipe doing nothing on the k-series is because theres another cat on the manifolds... gains can be expected when de-catting and replacing the manifolds?
That's only a ZR or 25, 200's don't have a pre-cat.
 

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My Rover 200 Has A Precat Pipe Dunno Wats In It Likes But If You Replace The Cat For A Decat And A New Midsection With Reduced Silencers Or Whatever You Do Feel Gain Oh Yer And A Back Box And A Performance Sports Air Filter With A Direct Cold Feed I Feel The Difference Throttle More Responsive And A Deep Nice Growl.......also Yer It Should Be Easy To Replace If You Have The Cat Taken Off And Stainless Steel Bolts In Replace Of The Mild Steel 1's Bcos I Had To Have The Garage Do Mine They Wer So Badly Rusted But Ther Ded Easy To Remove Now :)
 
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