I'm just wondering if there will have any negatives if I only change downpipe and without changing the up-pipe (keep the stock uppipe)? (I already have catback)

I heard somebody said if I change downpipe and with stock uppipe, stock uppipe might break and the dust or something will suck into turbo.....

What are the advantages and disadvantages of changing uppipe?

Thanks in advance.

 

no one can help??

 

If you can only do one, DO THE UPPIPE! You will have better spool due to no cat blocking the airflow into the turbo (more power, better throttle response, etc...). Plus, with the cat in there you risk having the cat break apart and being sucked into your turbo. It may sound farfetched but its happened to some folks on this board. Plus, with your 2002, you dont have to get engine management (although it would make it safer and more powerfull).

In a perfect world you should do them both at the same time (in order to get to the uppipe you have to take off the downpipe, you wont want to do them twice!), and instead of just the downpipe, get a full turboback (downpipe, midpipe and muffler) with hi-flow cat(downpipe, midpipe and muffler). And in an even more perfect world get an accessport or custom reflash. Do some searches, this is widely known info

 

Thanks for your valuable info

 

+1

I've been through three different up and downpipes. I've done my uppipe three times, It does not get easier the more times you do it. Do the downpipe at the same time as the uppipe since you have to remove it to get to the uppipe. Also look into an aftermarket heatshield for the downppipe like COBB, Cusco or Gruppe-s so you don't have to hack up the stocker. Or maybe even buy another stock one and have at it. If you are going to do the uppipe make sure it has a flex joint. I had the helix for awhile and liked it but I opted for a little stealthier setup. The bosal and STi uppipes come wrapped with factory type heatshields and look stock to anyone who isn't a subaru expert.

 

I have the stock up-pipe still installed and a TBE installed on my 02 WRX and I was able to gain 80 HP and 70 ft/lbs of torque with a retune. It isn't as restrictive as some believe it to be. I'll do that pipe eventually, but if you are shaving dollars off an upgrade, I'd say the TBE was the better investment.

 

The UP isnt about peak HP gain, it is about driveability. It will spool 500rpm sooner which is huge in day-to-day tooling around.

That said, you can do it whenever you want. Dropping the DP only takes about 10mins, it is extremely easy. So you are not really saving any significant amount of time by doing it at once.

 

I did the up and down at the same time because I'm lazy!