Hi guys,

Car: 53 plate STi Type UK
Mods: Panel air filter, cat-back

I have on my car at the moment a 3" cat back, manufacturer unknown (was on car when I bought it and all I have is a generic receipt from Jap Parts for a cat-back exhaust. The tail pipe is about 4.5" if that matters?

I have an STi tail pipe and center section (with cat) that I am booked in to have fitted this Saturday.

I know it will be a lot quieter, but what I most want to know is how much of an impact will it have on acceleration etc.

The car was never mapped for the cat-back so would that have had a negative effect on performance (as some things I have read lead me to believe) in that the ECU would be confused by it?

If fitting the standard STi box does have a negative effect - how much so are we talking? lots or only noticeable on a graph?

I could at some point fit a decat center to the STi box.

Thanks guys!

 

Might loose a bit this is due to the cat restricting, maybe 10BHP, but as you say need remap to get full effects, with a decat.

Someone will pop along with a better answer.

 

Are you saying you're refitting the centre cat and back box , replacing a 3" system of unknown origin? Unless the car was mapped (I think you're saying it wasn't) then there will be little or no difference. You can remove cats and have little noise by using a quality system, if you'd prefer.

 

That's what I was hoping, thanks

 

Yep, that's exactly what I meant. Going to put the OE back box and center section with cat back on. And no the car has not been mapped - it was kept standard by it's previous 2 lady owners and the last bloke who I bought it from put the catback on.

 

It will be much better, the torque you lost by fitting a 3" system to a car that didn't need it, will return

 

Thanks, that sounds good

Once when I took one of my classics to part ex for another classic, the guy who test drove mine commented on something that could well have been the torque. Mine at the time had a 4" cat-back (no map) his had standard.. hmm

 

Righty, been down to see Dan at Surrey Subaru Specialists this lunchtime and done the deed. Also put on a decat pipe that he had laying around.

So the set up now is second decat, OE STi center section and OE STi muffler.


After fitting, the car felt pretty sluggish so I went to McDs (again) then filled up with the good stuff and went hooning around up and down the A30 a few times and down all the backroads. Was out for about an hour of spirited driving (the rain didn't help) and come the end she was feeling much more livelier :thumbsup:


Results:

• Quiet all around except for directly behind car/infront of tail pipe.
  
• Obviously a very "stock" look going on, I am quite likeing that at the moment.
  
• Much much smoother drive, gear changes smoother, pulling away smoother and felling much better behaved in general.
  
  The best bit last....
  
• It stays on boost for longer, it used to taper off sharply at 5200rpm ish - I had my buzzer set to it - now it boosts right through 6000 rpm and tapers off at 6500 -7000 ish (I looked as often as was safe). Result!
  

I do miss the sound a little bit but no way was it worth trading up for the drivability, I have seen the error of my ways and in future when I mess around with the car like that I am going to have it mapped after.

Having said that, I may well get hold of a center section to get rid of the resonator - so one more question:

How much does the resonator impact the volume and would it mess with the car again?

 

It's better without the resonator Lot's of people go ***** out yeah man full 3" system innit without a fooking clue what they're doing 2.5" is fine upto 350bhp and keeps torque where it should be

 

I think I have to agree there 100% So the de-resonated center would keep it as it is only a bit louder?

 

Some pics of said exhaust..

Before (all crappy and rusty):





After Autosol and wire brush treatment:











The new cat pipe





The new look:





The old 3" system:

 

Looks good yep on mine I run a sportscat DP with decat second pipe, deres centre and STi BB. I VHT'd my box

 

Nice looking! Forgive for being obtuse - VHT? That the black coating on it (I like!)

So you have a sportscat - did you have to remap after fitting that? If not, what effect did it have on your car? Profound? Only I'm looking to buy one - there are a couple for sale at the moment, Prodrive ones. But wont bother just yet if I need remap after?

Thanks!

 

As long as you dont let it go high revs and let it over boost you will be fine mate, i have fitted a sports cat and awaitng remap at the moment so i keep an eye on the boost and insure i dont drive mad.

 

i like it

 

Hmmmm that's a big ask...

Cheers for the info