De-cat pipe

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bstardchild
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De-cat pipe

Post by bstardchild »

Bit of a DIY job but I'm happy with it

Image

Cut out the cat from a good second hand front pipe and welded flanges to it

Welded flanges the downpipes too and made up a bypass pipe and flanged that as well

Image

Now I can go back to the cat for the MOT and be de-catted for the rest of the year - 6 bolts and two gaskets and about 30 mins to change over

What do people think - I'll fit it later this week and let you know if it makes any difference to performance when it's de-catted
Last edited by bstardchild on Wed Nov 23, 2005 6:01 pm, edited 1 time in total.
david burton
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Post by david burton »

can't see the image from work, but I'm sure it looks like a good job!

you got that spare ECU yet? :) let me know how the de-cat performs....
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bstardchild
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Post by bstardchild »

david burton wrote:can't see the image from work, but I'm sure it looks like a good job!
It's not a bad job at all.....
david burton wrote:you got that spare ECU yet? :)
I bloody wish - becoming a bit of a mission now :twisted:
david burton wrote:let me know how the de-cat performs....
I think it may help the engine breathe a bit better and stop it feeling so strangled but it needs the breathing improved on the inlet side too to match (oh and a induction kit doesn't meet the requirements!!!)
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Post by david burton »

Just disconnected from VPN so I can see it now - looks superb. A nice idea. very neat indeed. Was it a pain to take the exhaust off the manifold?

you going to get the dremmel on the intake side of things then? or have you already done that?
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bstardchild
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Post by bstardchild »

david burton wrote:Just disconnected from VPN so I can see it now - looks superb. A nice idea. very neat indeed.
I bought the complete 2nd hand downpipe and cat off ebay for £10 so this was easy to modify at my own pace :wink:

http://cgi1.ebay.co.uk/aw-cgi/eBayISAPI ... 4570208138

Had a mate in another car club I'm in pick it up for me and then collected from him it at a meeting we both attended

I also wanted the cat to be easily replaced for MOT's etc
david burton wrote:Was it a pain to take the exhaust off the manifold?
It's only a 3 bolt fixing to the manifold and I've had mine off before cos the flexi joint was broken and I had to repair it - the idea was to offer them as an exchange but cos my old frontpipe is a bit of a bodge after the flexi joint split!
david burton wrote:you going to get the dremmel on the intake side of things then? or have you already done that?
No nothing like that - Have investigated boring out the std TB but there isn't enough meat in it so have the chance to buy a 1.6 TB so just weighing up the pros and cons..... might not fit, may be same size etc etc
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Post by JarnoVWPolo6N »

Good job m8! Looks nice, and I'm absolutely sure you'll notice an increased in enginepower, a cat decreases the enginepower by approximately 8%, so that shouldn't be hard to notice would it? :wink:
And the cat works as a muffler for your exhaust sound..... :twisted:

Have fun with it! :twisted:
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Post by OMEGASUPR3ME »

just make sure u dont get caught by one of those random emitions tests, but considerin how cold it is i doubt the rozzers will b out that much lol
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bstardchild
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Post by bstardchild »

OMEGASUPR3ME wrote:just make sure u dont get caught by one of those random emitions tests, but considerin how cold it is i doubt the rozzers will b out that much lol
Decatted all my other cars - been stopped before but only once have I been issued with a VDRS - change it back to cat take to MOT test station pay £6 get form stamped come back home and put the straight pipe back!!!

Rest off time - they are looking for serious polluters and don't even notice!!!
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Post by OMEGASUPR3ME »

thats allrite then :P
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Post by david burton »

did they stop you for any other reason apart from the idea you might not have a cat?!
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bstardchild
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Post by bstardchild »

david burton wrote:did they stop you for any other reason apart from the idea you might not have a cat?!
Nah - was just a spot check on everybody going down the road

- I could have argued the toss on the car (93L plate 3.0 24V Senator) I was in as it had (* well actually it didn't but it's a long story and a bit wafty) an engine swap from an earlier car pre 92K which I had the documentation to prove - so I didn't even need to put the cats back - they just did an emission check at the garage and stamped the form!!

*It's a well known dodge for certain cars made with cats before the law was effective (ie 1990 - 1992) but continued to be made after law on cats was effective

Basically it involves creating a paper trail that can prove that the engine has been changed from an earlier car pre-cat law and put in a car which is post cat law.

I now have a photocopy of a log book for a car long since scrapped which has the engine number for my L reg Senator down as it's engine number

I take the car for an MOT and they say cat test - I say Nope..... engine has been replaced - here is a copy of the log book for the car the engine came out of - it clearly shows the engine number is same as the one in my car and they don't cat test it!!!

The engine has actually never been changed what I did before I scrapped the old senny was send of the log book with my L reg engine number as an engine change

It came back all changed - I photocopied it and sent it back when I scrapped the car shortly afterwards

like I said a bit wafty and a bit involved but worth it

Haven't had to do a computer linked MOT yet so we will see if it works with that too!!!
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Post by bstardchild »

Fitted it now.........

Initial impressions

- revs cleaner and picks up better

- slight improvement in pull even in the higher gears

- Exhaust note slightly louder (not antisocial just crisper)

- engine is definately happier to rev above 4000 rpm

Early days but it seems a fair bit better - maybe 4-5 bhp better

Only negative comment is hard to describe but there is a segment of throttle opening that I have always known was a bit flat and it's accentuated it - not by much but definately more noticable now

When you are around 2/3 - 3/4 throttle in 4th or 5th if you lift off it seems to pick up better if you bury the throttle it also seems to pull better

I think this will be a deliberately engineered hole in the fueling map for emissions or noise - and bloody annoying!!!
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Post by skyline.99 »

some lovely diy there bstardchild! i like! :)
I just spent over 300 for a stupid s/s ex manifold and decat front pipe. it was a stuupid decision i know i paid a hellalot for it. but it will make the engine bay look nice. and oh, ffs on mot i have to remove the whole thing!! LONG!!! i will post a pic of my car soon hopefully with the manifold (still hasnt arrived )an ill tell u if it makes any difference.
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Post by skyline.99 »

just read your last post, i have flat spots in those places too, noticable on motorway! Do you have an induction kit on your car ?
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Post by bstardchild »

skyline.99 wrote:just read your last post, i have flat spots in those places too, noticable on motorway!
They will all have it - it's in the ECU maps I am sure
skyline.99 wrote:Do you have an induction kit on your car ?
nope bad for power unless you buy something quality like a BDA and then it's almost an airbox anyway!!!! :roll:
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