simonds1

Hey guys, first of all I'd like to apologise for asking a question you've all probably answered about 784 times already! I have searched the site and been looking around for a while now and am still not entirely sure of the answer tho, so here goes....

I've got a w reg uk classic impreza turbo 2000, and people keep telling me to de-cat it because I'll get a huge improvement. I know there are 2 cats on the car, and I've been told if you only de-cat one of them, the car will still pass the MOT? Is that right? If so, does it matter which one of the 2 you de-cat? Does one give better gains than the other? And the question I'm most trying to get an accurate answer for is.....(and I bet you can guess it!).......if I only de-cat ONE of the cats, will I need a re-map? The last thing I wanna do is break the car y'know? I wanna do it properly, so ur advice would be much appreciated

Cheers guys

hoskib

iTrader: (1)

downpipe cat is the best to leave in place.

unless things have got stricter with emisions, my old classic passed with the centre pipe in place only. it's an easy swap, so don't rule out the idea of a full decat

full decat with filter will get you about 240bhp, with a remap to suit you'll be looking at around 265bhp and a different car

Gear Head

iTrader: (2)

Firstly, it does make a huge difference!
The best way to go is to get a full de-cat system. This will consist of a de-cat downpipe, centre section and back box. (Around £550)
It won't pass an MOT, but it is only a 15 minute job to replace the centre cat.
This should take a standard TD04 equipped UK Turbo from 220bhp to around 250bhp.
A remap would up this to around 280bhp (£650).

hoskib

iTrader: (1)

allright chris great minds think alike mate

Gear Head

iTrader: (2)

Very true mate!
I'm cool thanks, just waiting for my sti 3 to come back from having an engine rebuild.
Bought it 2 weeks ago knowing the bottom end was knocking (got it at a good price mind! ).
How you going Paul?

simonds1

Cheers for your replies guys

I see the gains are greatly improved after a re-map is done, but is it safe to run the car without a remap? For example, if I went out now & de-catted the car but didn't get it re-mapped, am I basically gonna bugger it up in the long-term? Or will it be okay?

Also, I'd love to keep the standard backbox cuz I wanna keep the look of the car completely standard, but is that quite restrictive to the system? If I just de-catted the centre section and left everything else as it is....am I gonna notice any real improvement? Or what about de-catting BOTH cats, but leaving the standard backbox? Or do I need to be changing the backbox really?

Gear Head

iTrader: (2)

You do really need to change the backbox. I needed to put a standard one back on my old scoob for a few days, it felt as if some one had stuff a potato up the exhaust!
You should really fit a boost gauge before you change the exhaust, then you know how much passive boost increase the exhaust is giving you. But, generally classics scoobs are fine without a remap.

New_scooby_04

iTrader: (4)

Hi There,

1) Don't get a full decat- you'll fall foul of emissions; there is a 100cel sports cat DP now available for classics at £299. Ask David at Api about the ninja sports cat.

2) You will notice gains, but they wont be huge- the ECU will try and adjust fueling to compensate for better airflow. You will notice a lower and quicker turbo spool up and slightly stronger acceleration though. You need to remap to get the big gains

3) Generally a UK turbo will run a decat without issue (On SUL fuel) but it might be wise to get a knocklink just in case!

4) I recommend Bob Rawle for a remap

Speak to David at Api.

Tell him Ns04 says hi!

Ns04

BTW MY99 owner with Ninja sports cat....now running 320bhp (but you need more mods to get to that level!!)

simonds1

Ahh yeah I'd forgotten about sports cats, was gonna ask if they were any good. Cuz I know if I did get a full de-cat system, I'd only have to put it back for the MOT once a year.....which seems like nothing......but it's just such a pain in the ****. The R19 16v I had before was de-catted, and I eventually left the cat on cuz I couldn't be arsed with it! Everytime I re-catted and then de-catted it.....the exhaust would knock somewhere.....or rattle.....and omg just used to do my head in. I'm sure it's different on a scoob than some old french car tho lol. Also another thing was that all I've got outside my house is gravel & flower beds, so I can't even jack me car up without goin to a mate's house!

I think I should leave the car alone by the sounds of it, cuz I was hoping to just de-cat one of the pipes......notice a nice bit of difference......then job done. But looking at ur answers, I'm much better off doing it properly to make it worth while, and I haven't got that sorta money. Not at the moment anyway.

One quick question, what's this 'knocklink' that everyone keeps mentioning? I'm assuming it's something to do with a knock sensor? Or shall I just be quiet now? lol

New_scooby_04

iTrader: (4)

Ninja sports cat DP very good mate; only about 2bhp down on a decat DP. No hassle at MOTs

Knocklink basically a microphone and sensor connected to an LED display in the car. keeps an eye out for DET. The OEM ECU also has a knock sensor, but many tuners have commented that it doesn't appear to be sensitive enough, especially at high rpm.

Wise investement if your car is modified.

Ns04

simonds1

Cheers for all your replies guys, that Ninja downpipe with 100 cell sports cat looks good to me! I know this sounds daft, but you'll probably know where I'm coming from here........and basically.......I just wanna buy something lol. Something that will make an improvement to the car, even if it's only slight.....and judging by what I've read & heard everywhere, a de-cat of some sort is the way to go. So if I was to just get this Ninja sports cat downpipe, and not bother with a re-map or anything else, am I gonna have problems would you say? And also, I think I should get a knock link by what you've all been saying. Where can I get one of these?