Tris-seriesmcrae

I am new to the scooby world! I have been told a decat is a good horsepower upgrade is it true??

I have done some research but there are so many different types i am not sure what to get! some talk about 2" or 3" what is the difference?

And then there are cheap ones and expensive ones, surely it is just a pipe?

Thanks!

joey_turbo

iTrader: (26)

Yes its true for any turbo charged car. The cat is a huge restiction.
Depending on what model Scoobs you have, the car may need a remap, or the cat removal will cause some adverse affects.
Classics are OK, but I think you are pushing it with newage.

Tris-seriesmcrae

Lucky i have a classic then!

What would you reccomend? it is a pre 97 spec if that means anything!

myblackwrx

iTrader: (1)

I went with an HKS one for my 93 wrx

The Chief

A remap after you've fitted a decat will make a huge difference.

depends what you want hayward and scott are well respected.

best bet go to a local meet and have a listen and see what floats ya boat

Tris-seriesmcrae

I like quiet!

But i also like performance so i need a compramise!

Tris-seriesmcrae

Demon thieves do a magnex one without silencer for £90, what do you guys think of this?

Cat by pass kits | Catalysts & Replacement Pipes | Demon Tweeks Motorsport, Motorcycle, Modifying, Parts and Accessories

classic Subaru Si

Not sure if its the right one mate - price wise, I'm struggling to get a second hand one for that price!?!?

jd5217

i beleive that is just the centre section deact, think tiny in guernsey had one on his green scoob.

Tidgy

you tend to get what you pay for, £90 for a decat seems way way to cheap.

looking at the link, its just part of the exhausts not the whole system

about £350 for a full stainless system is prob about right

gaz-cole

i think the one listed is the centre section decat, but as said the hayward and scott ones are very good, make sure you get it heat wrapped though before fitment

The Chief

Magnex are nice and quiet (ish) but still omit a nice roar when pushed.

i can reccommend these and they sound lovely

Tris-seriesmcrae

Thanks guys, looks like a better save for a full matched system instead of piecing it together!

StiX

iTrader: (4)

If you want to stay legal, and not have to bother with swapping downpipes come MOT time then go for a Sports Cat downpipe.

Ninja has a good rep, and is good value @ £299:

Impreza Turbo 1993-2000 Classic : Subaru Impreza Ninja Downpipe with Fast Flow 100 Cell Sports Cat

If you want it to be reasonably quiet, then Magnex is a good choice (and there are lots of others e.g. Haywood & Scott) but you may want to go for the resonated centre - especially if you do motorway miles. Lots of backbox choices again depends on how noisy you want it.

That's the set-up I have (with a Magnex oval backbox), passes MOTs no problems but still produced good figures after I had it remapped.

Good rumble, but not too loud

Tris-seriesmcrae

I don't need a cat as we do not have MOT's in Jersey....

How about this one?

Impreza Turbo 1993-2000 Classic : Subaru Impreza Afterburner Decat Centre Section

Tris-seriesmcrae

I understand now! i just went to look at my car, i already have an aftermarket back box which has no identity!

The downpipe (off the turbo) looks as though it is restricted on the flange to the turbo, is this correct?

And then there is the cat pipe that is restricted for obviouse reasons!

I take it that there is no point in replacing one without the other?

What sort of realistic gains am i looking at after replacing these two?

Graz

You won't go far wrong with Stainless steel exhausts manifolds and headers from Hayward and Scott

The classic shape scoob exhaust system comes in three pieces from the turbo back. First section is the downpipe, replacing this offer the biggest gains for two reasons:

1. It has the large cat in it
2. Aftermarket types have a large open neck where it attaches to the turbo, this really improves the gas flow. The OEM system just has the flange connected to a normal size pipe so the waste gate is a bit suffocated.

Second section is the centre one, this has a smaller cat in it so again removal will result in some horsepower gains.

And finally the third section is the back box, the choice of this will determine how noisy the whole set up is likely to be, though the more free flowing types tend to be a bit louder.

A carefully matched system from the turbo back will given you the noise and power you desire. Three inch systems are only really necessary for big power builds, you'll find a lot more choice in 2.5"

I had a Hayward and Scott turbo back system on mine and it was superb, significantly improves the turbo response, and sounded ace

Tris-seriesmcrae

Thanks mate, i just did some research and noticed that the magnex system has a second pipe for the flange off the turbo and the hayward and scott system is completely open from the turbo.

So i am guessing you will get better power from the hayward and scott system?

StiX

iTrader: (4)

You will obviously get better gains by replacing all sections.

The biggest gains will come if you replace full exhaust and then remap.

As an example, my MY00 UK Turbo W Reg had Magnex centre/backbox when I bought it.

I changed the panel filter to a JR, replaced the downpipe with a Ninja Sports Cat, and drove to Powerstation to have it remapped.

Before they remapped, it was producing 230bhp (so only 15 up on standard factory figures).

After remap 273bhp. So a big difference, and also torque was way better and all-round driveability also.