Jerry UltraDork
March 15, 2017 6:05 p.m.

So I took the new-to-me WRX to my local SCCA-member-owned shop for an oil change, since I had no idea of the last time it was changed. And being a good shop, they looked the car over for me without even asking. Of course they knew I would be back for repairs/upgrades eventually...

They found the motor mounts worn, shifter bushings worn (which I could tell it was a bit sloppy), and an exhaust leak. They said it also wasn't pulling enough boost but I'm hopeful the exhaust issue is part of it.

They included this diagram, and pointed out the culprit:

My question, being new to this turbo thing (the Abarth's is completely stock and staying that way for at least awhile), is this considered the "up pipe"? I hear the terms up pipe, down pipe, etc and never really paid attention. My uneducated guess is the up pipe is upstream of the turbo, the down pipe is downstream of the turbo?

ebonyandivory UltraDork
March 15, 2017 6:26 p.m.

That's the up-pipe, it's got the precat in it.

Rodan Reader
March 15, 2017 6:39 p.m.

Called the "up pipe" because it goes from the headers 'up' to the turbo (on a Subaru).

Not sure of the year of your WRX, but in some years/models, there is a 'pre-cat' catalytic converter in the up pipe that can become damaged, and send shrapnel through the turbo. Obviously, this is bad.

We had an '05 Legacy GT which had the up-pipe cat, and the solution was to use the up pipe from a same year WRX STi as a replacement. Exact same part, without the 'pre-cat'.

If your year/model has the pre-cat, I'd strongly suggest a comparable factory part or aftermarket without the cat.

iceracer UltimaDork
March 15, 2017 7:36 p.m.

List says, "front exhaust pipe"

Knurled MegaDork
March 15, 2017 11:01 p.m.

The up-pipe is why you're allowed to remove factory cats in Prepared as long as there is A cat somewhere in the exhaust no more than 6" further back than the rearmost OE cat.

Used to be you didn't need catalysts in Prepared at all, and then that allowance got rescinded. Mod grew and Prepared shrank very heavily that year...

Jerry UltraDork
March 16, 2017 7:07 a.m.

I have a sheet that says a Megan Racing up-pipe was already installed by Slow Motion Motorsports in Columbus, so I'm sure there ain't no precat in the way. Glanced at a few last night, nothing expensive so might as well do this now. Hoping that takes care of boost issues.

Tyler H UltraDork
March 16, 2017 7:28 a.m.

It would have to be a pretty profound leak to be causing it to underboost. Take a look for any traces of an aftermarket boost controller.

Disclaimer: The following is not an actual recommendation.
You could disconnect the boost reference hose from your wastegate and carefully drive it to see if it will reach it's target boost. If it will, immediately hook it back up and start looking for issues with your plumbing or boost control solenoid.

Jerry UltraDork
March 16, 2017 8:10 a.m.

In reply to Tyler H:

I do know that it has a Grimmspeed boost controller under the hood but with the cold since I bought it I haven't explored it very much. I think I'm getting the pipe and mounts replaced next week, and then explore this controller thing.

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