up and down pipes...

[Gambit]

Hello,
Anyone installed UP/DP on their 9-2x aeros yet? And if so, what do you think? Any CEL issues? Worth it? Which would you recommend?

[lukerussell]

my '02 wrx had a o2 sensor in the up-pipe. a catless up-pipe will increase performance. i started getting a 0156 (i think) code after a year or so. i bought a $200 code reader and eraser from autozone. i ultimately fixed it by putting in a transistor that made the o2 sensor read normal. the other fix is to replace the sensor, which is expensive.

the downpipe won't cause a code but won't necessarily increase performane either, unless it's combined with a full turbo back exhaust system. if you go with a high flow cat or no cat you'll eventually get a 0420 code for the rear o2 sensor. same fix as above. i believe www.ponyexpress.com has the transistors for the o2 sensors so they read normal.

luke

[jdmpartstx]

Originally Posted by lukerussell

my '02 wrx had a o2 sensor in the up-pipe.

Actually, that's an EGT probe in the uppipe.

If you get a full-length downpipe (replaces both post-turbo cats) you'll need to get the CEL fix for the rear O2 sensor. This isn't a big deal and if you buy a downpipe new, most vendors throw it in for free.

[Gambit]

i've been doing some research that a dp will not yield too much as compared to an uppipe. So perhaps uppipe is better bang for the buck. Hmm... can I use an STi uppipe?

[jdmpartstx]

Originally Posted by Gambit

i've been doing some research that a dp will not yield too much as compared to an uppipe. So perhaps uppipe is better bang for the buck. Hmm... can I use an STi uppipe?

Honestly, an uppipe alone won't do much, either. You really don't get any real, honest-to-goodness power until you do a full turbo-back.

The first time I had my car dyno-tuned it had an uppipe (tubular, not cast), downpipe (Helix bellmouth) stock midpipe and STi axle-back. It also had a Unichip and a boost controller running a hair over 15psi. It made 210hp at the wheels. That's about 25-30hp over stock. Had I installed a full turbo-back exhaust it would have been closer to 225-230 at the wheels at the same boost level.

Uppipes are cheap. Used downpipes are cheap, as well. I recommend you do both at the same time.

You can use the STi uppipe. However, it's a cast unit and you'd do good to get an aftermarket tubular one. It'll be lighter and flow more smoothly.

[Gambit]

thanks for the reply. i'm just beginning to look into the up/dp mods. i don't want my 9-2x to be loud.

[sLaabaru]

cat-less is the way to go. But the environment won't dig it so much. Be ready for gobs of black smoke to pour out of you exhaust.

Go for the STI uppipe. Yoy can find them dirt cheap on NASIOC. Its cat-less and has a factory heat shield on it so it looks stock. Don't worry about it being cast. You not saving lbs. here.

Jon

[jdmpartstx]

Originally Posted by sLaabaru

cat-less is the way to go. But the environment won't dig it so much. Be ready for gobs of black smoke to pour out of you exhaust.

Go for the STI uppipe. Yoy can find them dirt cheap on NASIOC. Its cat-less and has a factory heat shield on it so it looks stock. Don't worry about it being cast. You not saving lbs. here.

I'm completely catless and I have zero smoke coming out of my exhaust. The only reason any smoke would come out would be from exessive blow-by (if you haven't installed a catch can) or bad tuning. I wouldn't say my emmissions are clean by any means - but there is no visible smoke.

The issue about cast vs tubular isn't for weight savings - it's for flow. I agree, however, that the STi uppipe has the benefit of looking stock.

And the difference between a cast iron uppipe - even the STi one with no catalyst - and a tubular stainless steel one IS pounds. Quite a few.