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Old 10-27-2003, 10:46 PM   #1
Unabomber
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Exclamation Uppipe FAQ: Read if you are thinking of buying one!

Uppipe FAQ

The primary purpose of an aftermarket uppipe is to remove the catalytic converter housed within the stock unit. This serves two purposes: to increase horsepower and decrease turbo spool time.

HP gain is around 10HP. This figure is highly debated as different manufacturers use different dynos with different cars with different levels of mods. Dyno Proof Example. The general consensus for turbo spool time decrease is boost will occur around 500 RPM sooner.

Is an aftermarket uppipe a performance or reliability mod? With regard to swapping over from a catted uppipe to a catless uppipe, it's both. Need some evidence of the reliability? View this link.

Which manufacturer is best? This topic is highly debated. There have been no reported consistent "bad" uppipes on the market. Obviously, there may have been bad pipes sold, but not enough to report as "bad" overall.

What uppipe metal material is best? Uppipes are made from mild steel, stainless steel (304 & 321), cast iron, and inconel. There is no irrefutable evidence that one material is better than the other. Obviously, corrosion levels are higher with mild steel (coated or otherwise) and cast iron. Corrosion on cast iron, due to it's thickness and material qualities, is more resistant to corrosion damage than mild steel. In terms of heat retention, the best material is inconel. Article on exhaust materials.

Which uppipe construction method is best? Uppipes are either solid or flex. There is no irrefutable evidence that one design is better than the other. The thought process is that a flex pipe will reduce the chances of leaking. Practical application has shown that correct installation plays a bigger role than the uppipe construction.

What is the cheapest uppipe? Gut your stock uppipe. Instructions. Gutting your stock uppipe can have the same benefits as using a more expensive aftermarket uppipe. Dyno Proof.

Which uppipe has the best gains? There is no irrefutable evidence that any uppipe has better gains than another. The consensus, if there is one, is they are all within 1-2 HP, gain wise, of each other.

Where do I buy an uppipe? Every Subaru/Import performance store sells uppipes. For purchasing, support your local economy or the NASIOC Vendors.

Should I replace the uppipe in my STi or 06+ turbo Subaru? All STi and 06+ turbo Subaru models have a catless uppipe. The big difference is that that the STI or 06+ turbo Subaru went from 2.0 to 2.5 displacement. Buscher Racing (post 318 and on) proved that going to an aftermarket uppipe vs. OEM catless does show gains. Does this mean an uppipe should be thought of in the upgrade path for 2.5L Subarus? Though it was once thought no, now one should consider it.

Are WRX and STI uppipes the same size? Yes. You may swap WRX and STI uppipe of all years as they are the same size. Remember that 02-05 WRX uppipes have catalytic convertors, so it's not a good idea at all to install one of those on a 06+ WRX or STI, but they will fit.

How hard is it to install an uppipe? Allow around 5 hours for install time. This can depend on many variables. jaxscuby is the current world record holder at 1.25 hours! A lift and air tools will significantly speed up the process but aren't entirely necessary. Professional installation, depending on your area, is around $300. Shadetree mechanics will install for around $100. Friends and install parties via your local Subaru club run the cost of beer and food.

How do I install an uppipe? Refer to the uppipe manufacturer's instructions. For uppipes without instructions, many rely on the Vishnu instructions for installation. Below are links to some of the better known uppipe installation instructions:
Vishnu's Instructions
Perrin's instructions
Scoobymods.com's Instructions, with pictures (using Perrin's instructions)
TurboXS's instructions
Scoobymods.com's latest instructions
Installation VIDEO
Scoobymods.com instructions

What part numbers might I need for this install? For best results, replace all the gaskets that are used for an install. The top and bottom uppipe gaskets MUST be replaced! Actual part numbers are not listed due to frequent changes; consult your dealer or online retailer for ordering.

OEM part names and approximate retail prices:
$15 Cross pipe, Left side
$10 Uppipe Gasket (Bottom)
$10 Uppipe Gasket (Top)
$16 Downpipe Gasket (DP to turbo)
$7 Cross pipe, Right side
$12 Manifold Gasket to the block
$200 2.0L uppipe
$200 2.5L uppipe
$59 EGT sensor

Are there any other parts I might need? Occasionally, an uppipe (especially used ones) will come without uppipe studs. If you are unable to obtain them from your Vendor, you will need five of SOA part number 800910340 which retail for ~$8.50 each. Alternately, you could source an automotive stud, m10 x 1.25 by 41mm at a parts store, preferrably Grade 8. Removing studs from an OEM uppipe usually will end up ruining the studs. You do not want to start an uppipe install with the hope that you can remove the stock studs. For removal or installation of these studs, be sure to use the double nut method.

Is there any other gasket information? Some users enjoy the extra piece of mind that comes with different gasket solutions rather than relying on the OEM gaskets. Some users source 5 ply gaskets. These are made by the same manufacturer as the OEM 3 ply units, but are 2 plys thicker. Some users have doubled up on the OEM gasket. Some users source copper gaskets. Additionally, many people have had great success using high heat copper gasket making substances applied to the top and bottom uppipe gaskets. There are some graphite gaskets as well. Sound confusing? Yep. Do know that the #1 way to ensure success is to use OEM from the dealer gaskets and proper torque...choosing an aftermarket option will most likely increase your chances of failure.

What about ceramic or other heat wrap coating? Though there are pros and cons to heat retention treatments with exhaust components, the general consensus with headers is that heat retention benefits outweigh the liabilities.
Pros:
Increased heat retention, which is beneficial for exhaust flow.
Reduces underhood temps, which decreases IC heatsoak.
Cons:
Additional expense.
Additional lead time, in the case of coatings.
Increased heat retention, which in some cases, can accelerate metal fatigue, especially at weld joints.
No proven HP increase.
If you plan on using a coating, ensure you are aware of what impact this will have on your header warranty if applicable. Coating or wrapping your header can void exhaust component warranties. If using a ceramic-type coating, ensure it's working heat range is above the known EGT. EGTs can be as high as 1400-1600 degrees in the extremes. Some normal coatings are not rated to this temperature level.

What types of ceramic or other heat wrap coating are available? The two most popular manufacturers of heat wrap are Thermo Tec and DEi. The two most popular coating manufacturers are Jet Hot and Swain Tech Coatings. Wrapping is a DIY project with a shorter life span than the professional only coating with a longer life span.

Excellent coating thread
.pdf file on coatings
Car Craft magazine's testing of Jet Hot

Do I need an EGT bung? No. The EGT bung is there for one purpose. It houses the EGT probe that monitors the exhaust temperature so the engine heat does not break down the catalytic converter element if the EGT becomes too hot. Since your new uppipe has no cat, you don't need an EGT probe.

My uppipe has an EGT bung, should I plug it or reinstall the stock EGT sensor? There is a chance down the road that EGT probe could burn up and pieces of it could be ingested by the turbo. Plugging it is the best option. You will need a M12x1.25 bolt. They can be tricky to find and many go to auto parts stores and ask for this type of oil drain bolt. True hardware stores are also a good place to find these. You may consider a jam nut if the bolt is too long, or you could trim it down to fit better. High temp thread locking compound is also an option.

What is the CEL fix? 2.2 KOhm 1/2 watt resistor. These are available at Radio Shack and are usually in stock. $1 buys you 6 of them. You place it in the EGT connector, which is the bottom connector just forward of your passenger side strut tower. It only has two holes, so jam one end of the resistor into each. If you do not use this resistor, you will probably end up with the CEL code P0546 = Exhaust Gas Temperature Sensor Circuit Malfunction (High Input). ***NOTE***There are two CEL fixes for the WRX, the other one is the rear CEL code P0420 Catalyst System Efficiency Below Threshold, this code being caused by the lack of a catalytic converter in the downpipe. This is usually fixed with an electrical fix or mechanical fix. This notice, though not important to this thread, acknowledges there are two "CEL fixes" and defines them individually to avoid possible confusion.

CEL fix location is forward of the passenger side strut tower:



Should I reset my ECU after this mod? It is never a bad idea to perform an ECU reset after a mod. The traditional route is to disconnect the negative battery terminal, press the brake pedal for a few seconds to bleed the system of charge, and reattach. Some use the more advanced Vishnu Reset.

What about emissions problems like emissions tests and legality? The main purpose of the uppipe cat is to keep cold start emissions low until the main catalytic converters warm up. Using a catless uppipe is a violatation of section 203 of the Clean Air Act. Each state has statutes that cover this subject as well. There have been no know reported cases of catless uppipes causing state emissions test failures.

Editors Note

This post was created because I wasn't able to find a good uppipe FAQ. I came up with the text based on LOTS of searching here. It was also created to be intentionally brand neutral so that it serves as a stepping stone for further research. Upon reading this you should have an idea of what type of uppipe best suits your needs. The manufacturer is up to you.

If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, "I have XXX's uppipe and it's great!" or "XXX's uppipe leaked after 1 month" are not appreciated here, that is what the Car Parts Review Forum is for.
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Last edited by Unabomber; 11-16-2013 at 05:26 PM.
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Old 10-27-2003, 10:56 PM   #2
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Excellent post. Sticky for sure.
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Old 10-27-2003, 11:27 PM   #3
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Awesome writeup, more posts like this would surely cut down on browseing time and people saying "search noob" since its all right there. Nice job!!!
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Old 10-27-2003, 11:31 PM   #4
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Nice work man!
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Old 10-28-2003, 10:39 AM   #5
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how about the CEL on an 04? i thought it wasn't fixable.
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Old 10-28-2003, 11:50 AM   #6
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The 04 CEL issue is in regard to the downpipe and it IS fixable. I hope to be doing a downpipe FAQ soon too, but here are the details since you asked:

1. Aftermarket engine management can resolve the P0420 CEL.
2. ScoobySport CEL fix.
3. Perrin O2 simulator
4. Casper Electronics O2 simulator
5. Weld an extention into your O2 sensor bung
6. Purchase a downpipe that already has a fix installed. Godspeed and PDE have extensions build in. I haven't confirmed it, but I believe they also have a small piece of cat material in the extension as well. There may be other manufacturers with CEL free downpipes, but those are the only two that I can recall without searching for 900 hours.
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Old 10-29-2003, 02:25 AM   #7
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Great post... added this to the FAQ and Threads of Note for this forum.
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Old 10-29-2003, 06:45 PM   #8
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ttt
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Old 10-29-2003, 09:54 PM   #9
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Default Re: Uppipe FAQ: Read if you are thinking of buying one!

Quote:
Originally posted by Unabomber
Uppipe FAQ

***NOTE***There are two CEL fixes for the WRX, the other one is the rear CEL code P0420 Catalyst System Efficiency Below Threshold, this code being caused by the rear O2 sensor due to the lack of a catalytic converter in the exhaust. This is usually fixed with a Pony Express MIL Eliminator fix or similar fix. This notice, though not important to this thread, acknowledges there are two "CEL fixes" and defines them individually to avoid possible confusion.
Sorry to be so slow, but, w hen I looking into uppipes I mistaken thought that the resistor mod took care of all of the CELs. When you say 2 CEL fixes, I assume you don't mean the both CELs are fixed by either of these solutions, and therefore besides the resistor I also need a Pony Express MIL eliminator?

Also, if I'm only doing uppipe (curse you CA visual!) and not the downpipe, do I still need this doohickey?

Well, since I've already got my Sti uppipe and my resistor, any recommendation where I go online to get this Pony Express thing to make the trifecta?
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Old 10-29-2003, 10:21 PM   #10
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If you have an uppipe, you only need a resisitor and that's it.
If you get a catless downpipe, then worry about the Pony Express MIL Eliminator fix or similar fix.

Thanks for the question as I used it to edit the quoted text to reduce any future confusion.

Last edited by Unabomber; 10-29-2003 at 10:29 PM.
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Old 10-29-2003, 11:34 PM   #11
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Thanks for the clarification....and thanks for the faq in general! You rock!
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Old 04-07-2004, 07:50 PM   #12
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Filing it for future reference. Great post.
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Old 05-10-2004, 04:49 PM   #13
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Now, how about a FAQ on what the uppipe is and does to go along with how to remove it.
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Old 05-10-2004, 06:00 PM   #14
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An uppipe connects the exhaust manifold to the turbo. It's only purpose is to connect the turbo to the exhaust manifold. In the WRX it contains a catalytic convertor. Replacing it nets around 10ish HP and decreases turbo spool time. In the STi, it doesn't contain a catalytic convertor. Replacing it does nothing other than aesthetics, which is debateable since you really can't see the uppipe. Removal procedures are in the installation portion in the top post.
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Old 06-14-2004, 05:48 PM   #15
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very informative
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Old 06-14-2004, 06:50 PM   #16
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What effect does the 2.2 KOhm resistor have on an OBDII test for emissions? Does the ECU think everything is kosher, or is it going to leave a test in the "Not Ready" state? Some states (MA) won't pass you if you have even one "Not Ready" test.
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Old 06-14-2004, 08:36 PM   #17
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It should have no effect. The resistor sends the ECU the correct voltage. I am stretching my memory here, but this is, in layman's terms, what happens:

The ECU sends out XX Volts.
The resistor makes it YY Volts.
YY Volts corresponds to the normal operating EGT temperature and the ECU is happy.
If no resistor, the ECU shows XX Volts and throws a CEL.
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Old 06-14-2004, 09:17 PM   #18
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I see. I assume the EGT sends out different voltages depending on the temperature, and that the fixed YY is somewhere within the acceptable range? It sounds like that and the mechanical 02 sensor fix is a winning combination for the OBDII emissions testing states for cars with up-pipes and turboback exhausts.
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Old 06-14-2004, 10:54 PM   #19
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This advice ONLY applies to the uppipe. The electrical fix with a turbo back exhaust WILL cause a problem with OBDII testing. As I understand it, the electronic fix (MIL Eliminator) will show a sensor not ready code. This is fine for most states as they allow one or two of these. For the best information on the exhaust fix, consult with locals who have first hand knowledge as to which is best for your area. For the uppipe fix though, it is 100% fine everywhere.
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Old 07-26-2004, 03:17 AM   #20
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Default unabomber - quick question for ya

i have the pde catless downpipe with the O2 extension. since ive never thrown a cel with this but yet ive never checked up on it, what will it read if someone were to scan my car with the smog test equipment? will it read as functioning normally? im confused since it doesnt throw a CEL yet im sure it will read higher than acceptable levels of NOx, Hydrocarbons, CO2, etc. thanks!
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Old 07-26-2004, 07:44 AM   #21
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You will be fine. The O2 extension's purpose is to decrease the sample rate of your O2 sensor so that it will read acceptable amounts of hydrocarbons, etc. Since you have no CEL, the levels of "bad stuff" are all within their parameters. The only kicker to this is if the Subaru O2 sensor threshold meets your CA emissions. You should repost this question in your local forum for the best answer.
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Old 08-05-2004, 09:19 AM   #22
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Awesome Thread... You answered all my questions. Thanks!
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Old 08-06-2004, 11:19 AM   #23
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Unabomber,

One of the most effective methods for keeping exhaust bits from leaking is to use new OEM metal gaskets and apply a thin layer of high-temp (orange) gasket maker on either side to seal it up. Using this method, there have been no leaks on the same car with about 25 different exhaust configurations. There also have been no leaks on other cars that were done with this method.

(You can also PM me for a story regarding just how well this works.)
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Old 08-17-2004, 06:07 PM   #24
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does anybody live near rowland heights California and know a good place to install my up pipe?
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Old 09-03-2004, 12:10 PM   #25
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You know what would be cool as part of each of these FAQs, and I understand the effort it would require, but... a SOA part number list for everything related to the topic (like what you have above, but grouped as a separate Q/A and complete... like adding part numbers for the stock up-pipe and the stock EGT sensor). Just would make it super complete and that much better as an end-all be-all reference material.
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