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Old 09-17-2018, 09:05 PM   #1
chris16371
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Default Exhaust questions

I want to apologize for anything in the wrong section, I'm new and still learning my way around the forum. Doesn't help that my browser says "page can't be found" and I have to use Tapatalk, which only displays a few words of the section description. Plus I'm completely new to Subaru's. There's a couple questions tuning related, I added it to my other questions since they relate and for the sake of not having many active threads. I can edit, delete questions, and then place them in the tuning section if desired. Your patience and knowledge is appreciated, thanks!

2003 WRX 5 spd wagon. 177,XXX on body and tranny, 1,XXX exedy clutch, and 70,XXX on motor (from a 05).

About 10 days after I purchased I was throwing a CEL P0171. I took it in for state inspection (no emission county) and they found 3 exhaust leaks. The party I purchased from guaranteed it would pass so they put a 3" SS exhaust on, downpipe included, with no cats. When I picked up car it seemed to run so much better. They also checked the lines to see if that's why I was getting the CEL. I'm still throwing the code, would it be a safe bet at this point that it's the A/F O2?

It's my understanding that with my model year I don't need a tune with a downpipe, correct? I'm of course now getting P0420. I have a Cobb V3 AP on the way, is there a point to using anti foulers since I'll be able to keep that code from coming up with the AP? I will flash the stage 1 map as soon as it arrives since I've read that it's a benefit even on a stock WRX. If I added a CAI would I just keep the stage 1 since a tune wasn't necessary for the downpipe or will I need to use a different map?

The car has the stock 03 up pipe with the cat still, I've read this is not good and I need to gut it or replace before it destroys the turbo. What's a quality up pipe that doesn't break the bank and is there different diameters to chose from, if so do I stick to stock size? Will a 06 STI up pipe fit my vehicle?, I feel I've seen this question somewhere. Is a tune needed for an up pipe?
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Old 09-17-2018, 09:34 PM   #2
snow_bound26
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No tune needed for the up pipe. STi up will fit and allow you to keep EGT sensor though they can break apart and kill the turbo as well. OE diameter is better for spool. Larger is only needed for high hp applications. GrimmSpeed is a solid choice that's not too expensive. Check classifieds section. Up pipes turn up all the time. Ceramic coating or up pipe blanket will help spool as well.

People say you don't need the tune with 02/03 MY but I don't trust that personally. If you have an aftermarket turbo back (down pipe and catback) I'd flash a stage 2 map since that is designed for the extra flow a down pipe offers. Cobb is very specific about what intakes can be used with their maps. Outside their parameters you would need a pro tune. Before you buy an intake figure out what ones are supported with which OTS maps. Make sure you stay within the parameters of that map. Never used anti foulers when I was using an AP.
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Old 09-18-2018, 03:05 PM   #3
chris16371
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Does anyone know what the stock uppipe diameter is for an 03? Tried searching and there's tons of threads on uppipes but can't find the answer for stock size. Also is hks a good uppipe?
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Old 09-18-2018, 04:06 PM   #4
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Default exhaust gaskets

Every time I take off exhaust parts on my 2016 WRX to do work, I always put new gaskets on when re installing exhaust. Is this the right thing to do at all times?
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Old 09-18-2018, 04:29 PM   #5
Valarius Starchaser
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Default Exhaust questions

The up pipe should be around 2.25-2.50 inches but in 03 you have a catted uppipe so there’s a large portion that is catted and this bigger in diameter

Go with the above and get a catless and retain the EGT sensor I opted for an invida one it to allows you to keep the EGT
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Old 09-18-2018, 04:29 PM   #6
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Quote:
Originally Posted by chris16371 View Post
Does anyone know what the stock uppipe diameter is for an 03? Tried searching and there's tons of threads on uppipes but can't find the answer for stock size. Also is hks a good uppipe?


HKS is fine. They make descent parts. Generally if an up pipe isn't close to OE size then the company making will say its larger in the product description.
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Old 09-18-2018, 04:31 PM   #7
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Default Exhaust questions

Quote:
Originally Posted by Canez17 View Post
Every time I take off exhaust parts on my 2016 WRX to do work, I always put new gaskets on when re installing exhaust. Is this the right thing to do at all times?


Not a bad thing to do. If it's one that I have replaced very recently or a GrimmSpeed 2x thick gasket less then 2 years old I do t replace it. But otherwise yes.

Last edited by snow_bound26; 09-18-2018 at 06:49 PM.
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Old 09-18-2018, 06:39 PM   #8
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Originally Posted by Valarius Starchaser View Post
The up pipe should be around 2.25-2.50 inches but in 03 you have a catted uppipe so there’s a large portion that is catted and this bigger in diameter

Go with the above and get a catless and retain the EGT sensor I opted for an invida one it to allows you to keep the EGT
The above says that the egt can also damage the turbo so shouldn't I go with one without or plug it and do the CEL fix that requires a resistor?
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Old 09-18-2018, 06:41 PM   #9
Valarius Starchaser
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That’s up to you seems like a small chance to me I kept mine and this is the first I have heard of it
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Old 09-18-2018, 06:47 PM   #10
chris16371
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Originally Posted by snow_bound26 View Post
HKS is fine. They make descent parts. Generally if an up pipe isn't close to OE size then the company making will say its larger in the product description.
Thanks, I've been looking at the hks and invidia bc they can be found under $150, anything has to be an improvement over the cat uppipe.
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Old 09-18-2018, 09:27 PM   #11
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I talked to the party I bought the car from and they have an aftermarket uppipe without the cat. They said it would be $160 parts and labor so I think this is my best option. I need a lift lol I'm use to working on my own vehicles but I can't even slide myself under it, even hard to up on ramps but I'm able to do some things with them.
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Old 09-18-2018, 09:33 PM   #12
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Quote:
Originally Posted by chris16371 View Post
I talked to the party I bought the car from and they have an aftermarket uppipe without the cat. They said it would be $160 parts and labor so I think this is my best option. I need a lift lol I'm use to working on my own vehicles but I can't even slide myself under it, even hard to up on ramps but I'm able to do some things with them.


Get jack stands. I recently swapped my engine and trans by myself with the car on jack stands. Although I just lose the crawler if it's on ramps. Just takes a little creativity and you can do a lot with what you have. That said, getting the catted up pipe out is a PITA. I did it without jacking up the engine but it wasn't easy. Once out, the new one goes in very easy without the cat in the way.
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Old 09-18-2018, 10:19 PM   #13
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I have some jack stands, idk but they make me nervous (as well as jacks) but I do use them at times. If they were asking a lot for parts and labor I would of purchased online and figured out how to do it myself but the price they are asking seems more then fair. Really great group of guys, pretty much all they do is work on WRX's and other turbo vehicles.

Being the uppipe is being swapped for a catless and the rest is a cat delete, will I have any issue passing state inspection (non-emissions area) being completely catless? Is there any reason (besides environmental) that I should buy and add a cat?

I'm not sure if the uppipe they will be installing has a EGT bung or not. I'm going to pick up an oil drain bolt just in case before I drop car off. I'm assuming I won't need to add a resistor since my AP will be here tomorrow and I'll be able to shut off the code along with the cat code.

Last edited by chris16371; 09-18-2018 at 11:43 PM.
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Old 09-19-2018, 01:21 PM   #14
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Well I just took it in for inspection again and failed for not having all 3 cats, guess I'm going to need to find someone that isn't as strict.
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Old 09-21-2018, 12:12 PM   #15
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So I had the catless uppipe installed yesterday and they also put an aftermarket BOV on for free. They said if I dont like the BOV that they would put the stock one back on, idk if I can really tell the difference.

I also got my AP installed with a stage 1 map, definitely improved some things. I was watching the different monitors on my way to work and I have a concern. First of all the P0171 is still coming on, they tested the volts of the O2 and they said it was good. The A/F Correction is what my concern is. On a normal flat driving it's running around +14 to +15, letting off gas while going down hill I'm reading 0, starting out from a stop or accelerating up a hill (even a small incline) it's jumping up to +20 to +25, at a stand still idle I'm fluctuating between -1.76 to +2.34 with spikes to -3 to +4 (rarely) but average seems to be -.78. Do these numbers seem right?
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Old 09-21-2018, 08:04 PM   #16
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Buy a used STI catless uppipe or $40 ebay special they work fine, if the smog station is strict you may need to hollow out your current uppipe so it looks catted. Get rid of the BOV today! If it is recirculated it might be ok but really there is no reason to upgrade OEM BPV ever unless you are full race car or speed density, but even then I would always recommend to recirculate.

If you have a second car to rely on for daily I would highly highly recommend returning that AP and getting an opensource pro tune after you install all parts you will use. Take the car off the road....install everything then limp over to a pro tune, it is so much safer than AP if you have a good tuner. 400 crank hp is daily driveable with a pro tune and supporting mods, with an AP I wouldn't push it that far. Get an AEM wideband and boost gauge and you are good to go.

Disclaimer: it doesn't matter what state you are in, removing functioning cats is a federal no no, everything said above is for entertainment purposes only.
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Old 09-21-2018, 08:05 PM   #17
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Buy a used STI catless uppipe or $40 ebay special they work fine, if the smog station is strict you may need to hollow out your current uppipe so it looks catted. Get rid of the BOV today! If it is recirculated it might be ok but really there is no reason to upgrade OEM BPV ever unless you are full race car or speed density, but even then I would always recommend to recirculate.

If you have a second car to rely on for daily I would highly highly recommend returning that AP and getting an opensource pro tune after you install all parts you will use. Take the car off the road....install everything then limp over to a pro tune, it is so much safer than AP if you have a good tuner. 400 crank hp is daily driveable with a pro tune and supporting mods, with an AP I wouldn't push it that far. Get an AEM wideband and boost gauge and you are good to go.

Disclaimer: it doesn't matter what state you are in, removing functioning cats is a federal no no, everything said above is for entertainment purposes only.

One more thing....your AF ratios will never be right with a blow off valve, it cracks open under vacuum and lets in unmetered air.
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Old 09-21-2018, 08:39 PM   #18
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It's a Turbo XS recirculating BOV, runs the same as the OEM as far as I can tell.

I already have a catless uppipe on, installed yesterday.

I drive 100 miles round trip 5-6 days a week, I bought this car bc I needed a daily driver with good fuel economy. I didn't want to do any mods but when the exhaust broke and the party I purchased from said the only exhaust they have were 3" catless and it would be free including installation what was I suppose to say, that I will buy a different one out of my pocket instead lol? I'm getting 26 mpg with the 3" downpipe, that was before the tune. Will calculate what I'm getting with tune after my gas goes down since I just filled it. Driving my 12-14mpg truck 100 miles round trip 5-6 days a week isn't an option. The only other thing I may do is add the Cobbs intake & box. There's literally no one within 100s of miles from me that does pro tunes. Ik they are better but being an 03 doesn't require a tune with a dp and neither does the Cobb's intake/box I figured a stage 2 tune with those 2 mods would be good enough, not ideal though.

My biggest concern is the P0171 lean bank 1 I've been getting pretty much since I started driving it, I need to find the source. The O2 voltage was checked, MAF cleaned, and I'll be doing the smoke test for vacuum tomorrow as well as find the source of the coolant leak that causes heavy smoking after more aggressive driving. If I can't find a vacuum leak I guess I'll buy a new MAF unless there's a way to check those, after that I guess it would have to be O2 related.
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Old 09-22-2018, 12:11 AM   #19
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Trouble ahead dude, it’s only a matter of time. If you already have an aftermarket down pipe go ahead and flash stage 2 for the correct fuel grade. It will actually be more fuel efficient. Keep the stock air box, make sure it is sealed properly. When the front tabs on the lower half are broken the box will not seal properly. Take the money you would waste on a Cobb air box and intake and put it towards oem o2 sensors and maf.
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Old 09-22-2018, 01:03 AM   #20
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Quote:
Originally Posted by PVNRT View Post
One more thing....your AF ratios will never be right with a blow off valve, it cracks open under vacuum and lets in unmetered air.
It shouldn't with the correct spring tension...
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Old 09-22-2018, 09:45 AM   #21
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How many psi do I push in when checking for a vacuum leak?
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Old 09-22-2018, 10:38 AM   #22
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How many psi do I push in when checking for a vacuum leak?


If you have a boost gauge it should read -20psi give or take 1psi at warm idle. Otherwise you can let the car idle and spray a little carb cleaner around the vac lines. Change in rpm indicates boost leak. This has worked for since I don't have a way to pressure test.
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Old 09-22-2018, 11:07 AM   #23
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Originally Posted by snow_bound26 View Post
If you have a boost gauge it should read -20psi give or take 1psi at warm idle. Otherwise you can let the car idle and spray a little carb cleaner around the vac lines. Change in rpm indicates boost leak. This has worked for since I don't have a way to pressure test.
I was just going to do the diy with the PVC cap and air coupler and spray soapy water on the lines, just don't want to push to much pressure through the lines so was just wonder what to set my compressor at.
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Old 09-22-2018, 03:26 PM   #24
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Buy a regulator to up the pressure slowly at the tool I used a paint gun regulator I test to 25 psi on my car with a target boost of 21
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Old 09-23-2018, 01:11 AM   #25
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Buy a regulator to up the pressure slowly at the tool I used a paint gun regulator I test to 25 psi on my car with a target boost of 21
My compressor has a regulator on it already but it's at the compressor, any reason I need another right at the diy tool?

So I want to hook the tool to the intake and then slowly add air, not to exceed 25 psi?
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