the_big_1

iTrader: (1)

Hi all
am I right that a 2.5 2006 sti has two CATs?
If so, which would you remove and which would you replace with a sports CAT?
I know it would need a remap.
Would the exhaust, ninja 2 and no resonator, be louder?


Cheers.

the_big_1

iTrader: (1)

Bump

Ved

Yes, sports cat is the one on the downpipe so the first one and an Ninja 2 can be heard from a mile away, according to this review page

Impreza Turbo 2006-2007 : Impreza Ninja 2 performance exhaust backbox impreza silencer

Most sports cats for ours will be a 3" one meaning you're likely to need a full system from someone like TSL (which is apparently amazing quality).

the_big_1

iTrader: (1)

Is there not one to fit the ninja2? With only the sports cat, will mot emisions still be passable?

Ved

Emissions wont be a problem. You can get a fitting bracket from 3.0 to 2.5 but you will have reduced air flow simply because it's moving 3" pipe into 2.5". If you're looking for power and a pass then go for a full system unless it's out of your budget. Since a good backbox is 250 and a sports cat into the 400s it's not too much to save for another month and get a full system all the way through.

Mikkel

I have a decat downpipe, vortex centre pipe and a racebox back box. I may be wrong but I believe the pipe work is 2.5" with a 3.5" exit on the back box. My car is running 360/390 and is a 2.5 STi.

It wouldn't pass an emmissions test but if I went for a sports cat and heated it up before the test then that probably would. It's not too loud at all by Impreza standards but I am thinking of getting a vortex back box to make it a bit louder. I'm not sure which is louder the Ninja or the Vortex. If you use the car daily consider the racebox, good exhaust and not OTT.

the_big_1

iTrader: (1)

Does the down pipe replace both CATS? or is it two pipes to replace both CATS?

Mikkel

My downpipe replaced both cats, but I believe you can buy others that only replace one. The centre pipe is just for the resonator.

rewindnottm

on the PPP STI 06 there are two pipe the down pipe and the short pipe.

if you go down the OEM route then you will need to replace both, if you go down the thirs party route you need to replace the two for one big one.. PM if you want an illistration from another website

Cheers

Damian

greatgonzo

iTrader: (1)

Have a look at the Hayward and Scott web site they explain things well. You dont have to go down the sport cat route, I think there over priced anyway
If you get a two piece decat then come MOT time just replace the cat under the car rather than the down pipe one as this is a lot harder to change
Simple really.

uk300scoob

iTrader: (24)

just get a full decat turbo back system, when mot comes stick the silencer in

greatgonzo

iTrader: (1)

Yeah but the silencer (resonated section) will not help the emissions test It will still fail

uk300scoob

iTrader: (24)

a full decat with a resonated downpipe and centre section with a silencer on the backbox with proper fueling etc will pass

greatgonzo

iTrader: (1)

Hawkeye has 1 cat in the down pipe then a short section with another cat (2) then the resonated section then the back box.
The resonated section (silencer) only reduces the noise slightly,I can not see a 2.5 litre hawkeye with no cats that has been mapped to run with no cats passing an MOT

53

iTrader: (41)

PPP on the MY06 STi doesn't change the DP only the second cat.

And even if you go non OEM you can get the two pipes separately.

I run a H&S Sports Cat DP, H&S Decat Rear Centre and Straight through Centre into a Blitz NurSpec S back box.

Passes MOT no Probs and sounds great. Remapped properly should see 340/380 ish.

YouTube - 53WRX's Channel

Mikkel

As has been said, you will only pass the emissions test on an MOT if you have either the OEM cat or a sports cat in the downpipe... or if you know the MOT man

The second cat hardly does anything.

If you have the wedge to spare, get a sports cat. Expensive, only marginally more restrictive than a decat and hassle free. If you have a friendly MOT man or are handy and willing to switch the cat on MOT day then get a decat.

greatgonzo

iTrader: (1)

What do reckon with just the 2nd cat in (well warmed up) Would it scrap through

Mikkel

I'd doubt it mate, but I am no expert on MOTs I have to admit.

the_big_1

iTrader: (1)

Any improvement by changing the first cat to a ppp and getting rid of the second?

greatgonzo

iTrader: (1)

I don't think Prodrive make a sport cat for the 2006 model as all they do is remove the 2nd cat for there ppp.

the_big_1

iTrader: (1)

Any ideas who does a sports cat for a 2.5 pipe size?

greatgonzo

iTrader: (1)

Hayward and Scott.
But there not cheap.

the_big_1

iTrader: (1)

Might have to consider a full decat with 2.5 pipes after next mot and change it all every mot

Ved

If you're looking for pure power then a decat is best but a sportscat means you have less hassle and money in your pocket.

uk300scoob

iTrader: (24)

guess il need to put cat back in mine when mot comes i have full decat with headers

the_big_1

iTrader: (1)

I would love to do sports cat but I guess the cost may be a little high?

Butty

iTrader: (2)

The Prodrive sports cat plus decat sections from a pre 2006 car would fit the gap OK.


Nick

the_big_1

iTrader: (1)

I thought there wasnt a ppp sports CAT ?

53

iTrader: (41)

Spot onI think the Sports Cat is more restrictive than some would have you believe.

Spot on I run the old Sports Cat/decat/centre exhaust system off my MY03 WRX on my MY06 STi. Note...You have to use the rear cat and DP together from the same year to match lengths !!!

Butty said pre 2006 mate, where the PPP included a Sports Cat DP

If I were doing it again I would leave the DP alone, go second decat and remap with JGM looking to get IRO 330bhp/360ftlbs. In the scheme of things with a well crafted map should give you plenty to think about thoughout the useable power band.

Basically replicate the PPP with a more custom/aggressive map.

the_big_1

iTrader: (1)

So if I get the DP and cat off a pre 2006 sti PPP then a re-map?