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Old 20-09-2009, 10:12 PM   #1
DaveMc
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pre ford De-cat

Recently blew my cat and instead of replacing I am considering putting a de-cat pipe in instead

Has anyone on here done this and noticed a differnce? Ive been told someone did it to his Auto version and he felt it lost a little power but not sure how it would effect the manual

I have the KFZE engined Mazda Lantis with the small cat
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Old 21-09-2009, 06:16 AM   #2
project.r.racing
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I doubt anyone on here has done it, as removing the cat in Australia is illegal. Dunno about your laws in Scotland.

I have replace my cat with a bigger higher flowong one, and a gained alot of mid range power and exhaust noise.
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Old 21-09-2009, 06:57 AM   #3
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There are a fair few silvias and skylines getting around with gutted cats.
THey apparently feel a power difference. But the skylines got alot bigger engine.
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Old 21-09-2009, 10:20 AM   #4
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if your going to replace it with some pipe... why not just buy a new cat?

if your old cat was so busted ass that it fell apart, then a new one should still be an inprovement. or a highflow cat.
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Old 21-09-2009, 03:41 PM   #5
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or you can allways get a fake cat.. its not legal if it gets tested by the sniffer, but just by the eye it looks like a cat.. sheild and all.. few up on ebay at the moment, jsut a piece of pipe that has a shroud around it to make it look real

oh and if you take the cat out you should have more power..
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Old 21-09-2009, 03:46 PM   #6
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ok this has been done.. i did it on my bg.. smashed out the centre of the cat and reinstalled it... work a treat. but i found i lost power.. as it wasn't a straight pipe.. terbulance built up in the cat shell and stopped the exhaust from flowing smoothly....

but it sounded great tho
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Old 21-09-2009, 06:59 PM   #7
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I removed the cats on all my cars when i lived in NZ -it was legal to remove them
My 82 Famila cooked its cat one day being thrashed on the hills so i removed it. Made a massive difference. it actually accelerated afterward. I pulled it apart and looked at it and it was cracked!!
My 87 Etude 1.6 DOHC had a straight pipe fitted instead of a cat and it sounded horrid inside but had a nice bark when being thrashed.
My 1.8 BG familia GT loved to rev after having it removed
My 88 Familia GTA-e 4WD Turbo gained a huge amount of power when it was removed.
And removing the whole exhaust off my MX-5 and putting a 2.25" system sounded incredible. It made it a lot smoother at high revs.
Removing the cat makes a completely different type of note and a trained ear can hear which cars have them removed.
They make a more metallic noise?? (it seemed like you could hear each of the valves opening and closing in my MX-5)
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Old 21-09-2009, 09:08 PM   #8
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I can't remember if the KF -ZE had it's cats on the exhaust manifold like the normal KF.

but normal KF's have them -twin on each side. Unlike the KL which had one US style cat after they joined.

double check that because memory does not tell me the ZE was any different but if it doens run the single cat.

It's choice thing.

IN Aus - - if you get caught it's automatic EPA fine and in NSW it's court appearance now I understand as part of anti social hoon crap.


if it's legal won't hurt.

Cat removal does not make a massive difference in a normal sense. Dyno runs on good cats V **** ones and no cat have proven minimal interfearance. especially on N/A motor.

but IF you have blocked CAT? different story.

the problem with alot of cars is they they fail but then crack and fall into them selves. Good Jap types don't

but cheap chinese made and Us type's fitted to AUS cars all die about 30-40K km's down the road.
You know that rotten egg smell that's the cat dieing.

I know right now mine is doing it too. moslty because it has not been run on good tune.

Bad tune of engine - like - running hotter exhaust or colder richer exhaust kill the cats. It also creates that bad smell when it finnally gets to temperature.


One of my performance tricks has been.

replace it with hi-flow - or half biscuit type and fit it further down the car.

mine sits before rear axle on one car, it don't heat up and being a decent one - when you remove it it's always see through the honeycomb. even on hi boost and over fuel.

Piping them too is a good thing.

if your In NSW the RTA inspectors now carry a exhaust reading monitor, it only picks up on mainly exhuast gas readings to try and prove either you not running a stock ecu or emission setup.
I am not aware this can tell if a cat is doing it job or not.
but be aware it's a big fine
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Old 21-09-2009, 10:49 PM   #9
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rodhog if yours doesnt heat up it cant be working properly? from my understanding of the reactions that the cat causes in the exhaust gases it needs to be hot, has it been tested?
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Old 25-09-2009, 12:32 AM   #10
DaveMc
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Thanks for all the replies so far guys, I do have a Cat-back exhaust system fitted and found after a week the above happened bad smell / wrecked

I am going back to the same people who will make me a straight threw pipe for around £50 GBP what is cheaper than a new cat / performance cat threw here in the UK

Here is a picture of my Cat-Back system



This isnt on the lantis but the exact same system it only has 1 cat just after the downpipe

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