Probably been asked many times, and I have searched and have found many conflicting views.
I would like to keep my 2001 WRX wagon as close to standard as possible, but would still like to free up any available ponies that are still sleeping, so I thought exhaust would be a good start, ( I'm still keeping the twin tail pipe look ), have found one that hopefully fits my car ( 3" turbo back ),but I'm wondering whether I need to fit a complete de-cat to gain maximum gains, or just certain sections will suffice, and then there's the obvious mot issues as well.
So can someone clear up this dilemma for me, do I need a complete system, or do I just need a de-cat up pipe, or a turbo back de-cat system.
What mixture will pass the mot, and what mixture of system will require a friendly man at the mot station.
Finally, a re-map question, with any/either of the above modifications, will a re-map be required for it to run to its full potential.
Thanx.

 

If you fully decat it (turbo back) a map would be required (I would at least change to a decent panel filter at the same time, and probably a new fuel pump as well) leaving the downpipe in place you could change the centre section(s) and maybe get a couple more geegees and a bit more burble and get away without the map but it won't run to its full potential.

 

Panel filter is on my list, I did fit an induction filter kit but it just wasn't my cup of tea and it messed the maf up.
I'll stick with the standard fuel pump until after the remap, if it needs doing to improve matters then I'll grab one, I'm not looking for silly figures as regards bhp, 250 would be nice and the car running properly as well.
I also keep seeing different types of up pipes, some with flexi and some solid, is there a reason for this.

 

Just another thought, will a turbo back 3" system fit straight onto the standard pipe that is left.

 

unless you want the noise, or are looking at over 400BHP, stick to a good 2.5" bore system, this will keep your torque figures up.
replace the up pipe with an STi (no cat) one;
look for a used prodrive sport cat (down pipe).
mate that to a nice decat 2.5 system from the downpipe to the tail pipe.

thats what i run, with a few other mods and produce 355/360lbft and can still drive through the street at 0500 without waking the neighbours.

hope that helps.
PS my 2.5 is a Haywood and Scott. IIRC Scoobyclinic make the same/similar system.

 

oh, go for the remap with that system and a filter and if you stick to a 250 BHP the torque figures should be past that.

 

So is the 3" system going to be loud, I don't mind some nice throaty burble, but I don't want to **** people off every time I drive past, ( I'm the wrong side of 21 for that ).
Anyone have any links to compare the 2.5" to the 3" system sound wise.

 

Most mappers will tell you to fit an up rated fuel pump before they map.

 

Is this really necessary for the small gain that I'm after, surely the standard pump will cope with 250ish bhp.

 

Decide who you want to map your car and ask them mate. Mine was £40 on here so not a lot really.

I dont think a mapper will map to a specific BHP. They will map the car so it's at optimum performance, fuelling, timing etc.

 

Fuel for thought

 

for what you are doing the pump change isnt necessary, you are not looking for more than a practically stock STi makes, on the same pump - all be it larger injectors.

the 3inch is a louder system - how much ????? anyones guess; I was only giving some of my thoughts from what i have on my own car. As i said, do you want a louder system or do you want a correctly sized system - not making a judgment just stating a fact.

its a mine field with exhausts its really hard to say whats too loud, maybe try to see if there are any members near you who can tell you what they are running and you can hear them as well.

hope that helps.

 

Appreciate any help that fellow members can offer, it's probably the reason I haven't been to view the 3"exhaust system today, it's not on my doorstep plus I don't want to buy something that really doesn't suit my needs.
Having said that, it's pretty cheap for what it is, but no good if it needs too much work to fit to the car.
I would have considered one of the group buys, but they don't offer the twin tail pipe option.