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Old 08-30-2007, 04:13 PM   #1
FTD
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Default A quest for an STX legal WRX

I wanted to post my findings on the hardware and strategy that I am using to keep the emissions system happy on my 2002 WRX. This setup retains all required emissions software and hardware with no CEL (Check Engine Light), which meets the rule and intent of the new STX clarification. I felt that sharing this may help others.

The intent of this thread is neither to support nor ridicule the clarification or the way the rules have been twisted in the recent past, rather to encourage people with WRX’es to see that it is not all doom and gloom. The STX class can still be fun and competitive for people running WRX’es!

I will describe my setup in detail, giving both a before and after list of hardware. Then I will provide some commentary that may help to minimize the chance of CEL’s during the event.

Setup before clarification setup (as run at Nationals in 2006):
Stock exhaust manifold with stock O2 sensor
Perrin uppipe (with resistor in plug for EGT sensor)
Cobb down pipe w/ high flow cat and stock O2 sensor
Stromung 2.5” Cat back exhaust
ECU – Access port with stock boost maps and P0420 turned off.

Setup as of Monday 8/27/07
Stock exhaust manifold with stock O2 sensor
Vishnu uppipe with bung for EGT sensor and stock EGT installed
Xcelleration shorty down pipe “True 3 inch” with high flow cat
Xcelleration third cat eliminator pipe with high flow cat and stock O2 sensor
custom 3” Cat back straight pipe
ECU – Access port with a revised base map that turns on the P0420 and stock boost maps

The high flow cat pipes (made by Random Technologies) came with nice little EPA cards with exemption numbers listed, which according to the cards are supposed to reside in my glove compartment. I don’t know what that is worth, but they are there. Related site: http://www.xcceleration.com/itemdetails.cfm83.htm

So yes I am running two cats, GASP, many thought this would be the end of the world! Long story short: After the tune I compared dyno sheets – I am UP 10 HP and 10 FT-LBS from a year ago. So opening up the exhaust to 3” and removing the muffler more than compensated for the additional restriction of another cat. These cats flow very well ~613cfm (for reference an open 3” pipe flows around 720cfm), yet their precious metal content is sufficient to effectively clean up the exhaust gases. The O2 sensors are happy. No need to fool them.

What about the EGT? This is a little more involved. Since my tune never turned off that code in the ECU, I was able to pull the resistor and plug in the sensor right after I had swapped uppipes (thanks dwx!) to see the effect. I did that on Saturday 8/25, I have been running it since, even when the car was on the dyno. The drive to Chicago was 3+ hours each way with lots of starts and stops. It has not produced a code yet.

I data logged my controller with an AutoTap diagnostic tool before and after I plugged in the sensor. The controller was in the “ready” state the whole time. So swapping from the resistor to the sensor does NOT cause a code or require a reset. My plan is to make up a plug with a 2.2k ohm resistor to run on the street then plug in the sensor at the event. This will minimize the chance of a fluke high/low input causing a code. Also, I will be carrying a spare EGT sensor in case of failure.

This way the ECU will be in the “ready” state and all the required emissions hardware is in place for the event.

I will be running my first event in this configuration this weekend in Chicago. We'll see how it goes!

Take care,
Chris Fenter
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Old 08-30-2007, 04:47 PM   #2
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Quote:
Originally Posted by FTD View Post
So swapping from the resistor to the sensor does NOT cause a code or require a reset. My plan is to make up a plug with a 2.2k ohm resistor to run on the street then plug in the sensor at the event. This will minimize the chance of a fluke high/low input causing a code. Also, I will be carrying a spare EGT sensor in case of failure.
Why not just do this for the O2 sensor, also, and skip any physical H/W changes to the system? Keep in mind there's no requirement to have certified exhaust components, only to not have a CEL and for the CEL to be functional.

1. Run resistors
2. Remove day of event
3. Replace after event

No CELs and everybody's happy!
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Old 08-30-2007, 05:13 PM   #3
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Great post Chris. As I mentioned in your SCCA Forums thread - I'm glad you were able to pick up some extra hp & tq!!!

Chike Dellimore
#70 DS
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Old 08-30-2007, 05:13 PM   #4
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Thanks for posting your work Chris. I saw Pat Washburn referencing several times on the MAC board that you had something in the works.

I've wondered about how much flow you could get out of 2 high flow cats, sounds like you're doing quite well with it.
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Old 08-30-2007, 05:18 PM   #5
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Thanks Chris.


You're an asset to the "class".



Greg--now more distraught that Chris is up on power.
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Old 08-30-2007, 05:29 PM   #6
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Nice job!

We missed you Sunday.
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Old 08-30-2007, 05:51 PM   #7
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Originally Posted by zzyzx View Post
Why not just do this for the O2 sensor, also, and skip any physical H/W changes to the system? Keep in mind there's no requirement to have certified exhaust components, only to not have a CEL and for the CEL to be functional.

1. Run resistors
2. Remove day of event
3. Replace after event

No CELs and everybody's happy!

Thanks for the response. My intent was to truely keep the P0420 code from coming on during continuous street operation (I drive my car to all events). So the resistor for the O2 sensors (which I have never played with) would not accomplish my goal.

The only reason I may run the resistor on the street for the EGT is to keep a random high temp or high input code from popping up right before the event. I am trying to have my car in a ready state when I run, even though I don't think it necessarily has to meet the rules as written.

Like I said the EGT has been in the car for over 350miles and no code has come up yet. I probably won't unplug it until it throws a code. We will see how long it goes.
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Old 08-30-2007, 05:56 PM   #8
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Thanks for the feed back everyone. It has been difficult completing all this research, sourcing parts, and tuning in a three week time frame. Thanks to everyone who helped and supported me during this effort!

I am grateful to have such wonderful friends. I will do my best to represent you well in Topeka.

Take care
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Old 08-30-2007, 07:35 PM   #9
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Do you think the second cat is necessary? Is the 2nd O2 sensor behind it?
Stock has the second O2 before the 3rd cat no?
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Old 08-30-2007, 07:39 PM   #10
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Are there any downpipes on the market, other than the Random Tech based ones, that have integrated cats?

As soon as the "all emissions hardware must function as the manufacturer intended" thing came out I was looking at those parts, but those appear to be the only ones on the market and they're expensive as hell. I guess I can sell my current stuff but that still puts me out at least $1000, plus another $400 getting the car re-tuned around the new bits. Ugh.

Maybe I can buy one and have a local shop duplicate it and resell it to other STXers to recoup the cost

john
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Old 08-30-2007, 10:16 PM   #11
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Hmmmm...
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Old 08-30-2007, 11:30 PM   #12
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Quote:
Originally Posted by FTD View Post
Thanks for the response. My intent was to truely keep the P0420 code from coming on during continuous street operation (I drive my car to all events). So the resistor for the O2 sensors (which I have never played with) would not accomplish my goal.

The only reason I may run the resistor on the street for the EGT is to keep a random high temp or high input code from popping up right before the event. I am trying to have my car in a ready state when I run, even though I don't think it necessarily has to meet the rules as written.

Like I said the EGT has been in the car for over 350miles and no code has come up yet. I probably won't unplug it until it throws a code. We will see how long it goes.
Good luck, Chris.

Sorry for any implied sarcasm, I'm still having a harm time getting my head around all these, ahem, "clarifications". Unfortunately, no SEB/STAC member has dared mention the "why", and it seems no answer is forthcoming.

Good luck at Nats, though I don't think you'll need it...
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Old 08-31-2007, 12:09 AM   #13
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Anyone have an idea how well the high flow catted downpipes prevent the P0420?

not sure what cats these use, but Prodrive makes a catted downpipe- it's spendy though @ $650! MadDad makes a catted downpipe too

Also curious on the choice to run two cats?

Xcceleration also makes a high flow cat upipe!!!!!!!!!
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Old 08-31-2007, 12:30 AM   #14
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Quote:
Originally Posted by BIGSKYWRX View Post
Anyone have an idea how well the high flow catted downpipes prevent the P0420?
the error is caused by the measured voltage between the front and rear O2 sensor hits some preset value. The difference in voltage between the front and rear sensor is a measurement of how much catalyst was able to remove the hydrocarbons and all the other crap that it's supposed to remove.

as long as the hi flow cat is able to remove enough polution, you should be fine.
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Old 08-31-2007, 12:37 AM   #15
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Do you think the second cat is necessary? Is the 2nd O2 sensor behind it?
Stock has the second O2 before the 3rd cat no?

I highly confident (but didn't confirm) that if I continued to run my Cobb down pipe with the single high flow cat I would throw a P0420 code. The 2.0 liter WRX'es are very sensitive to cat removal. So I believe two high quality cats are necessary.

You are correct that the Stock setup has the O2 sensor behind the second cat, before the third cat. This Xcelleration setup has the sensor behind the second cat as well I just shifted both cats down stream. I don't believe that there is any problem with that, because the rules allow for cats to be located down stream. The O2 sensor must shift with them or we wouldn't be testing the gases before and after the cats. I don't believe this is outside of the rules or the intent of the rules.
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Old 08-31-2007, 12:42 AM   #16
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Xcceleration also makes a high flow cat upipe!!!!!!!!!
Yup, I almost bought the uppipe cat and the first down pipe cat figuring that would emulate the stock setup well and keep the EGT happy. In the end it turns out that the EGT can live without the 1st cat, so far it seems fine with it.

I really dislike the idea of running the uppipe cat...

That being said I just bought my spare EGT today!
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Old 08-31-2007, 03:45 AM   #17
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Great post Chris.

If there is any help you need just give me a call, glad you got this all worked out.

Do us Wisconsiners proud!
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Old 08-31-2007, 10:22 AM   #18
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In my experience with the EGT before we pulled it and replaced with the resistor the biggest thing that tripped it was bad gas. Our car in Ohio always ran on Sunoco 94 even with the stock ECU. The first time we threw an EGT code was when we were stuck filling up with BP in Michigan on the way to Oscoda. Then we threw it almost instantly when we drove the car to Topeka and were forced to use 91 octane gas.

I think that you should be fine on that sensor as long as you use good quality gas but I'd still pull it quite often to make sure it's not starting to look ready to break off and eat a turbo.

And as I said on sccaforums I'm still amazed at how much money you've put into this effort. I was unwilling to spend any money, much less well over $1000, to make my legal car legal again and just dropped out. You definitely have my respect for spending the time, money and effort to try to stay legal especially when what IS legal is changing and unclear.
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Old 08-31-2007, 10:40 AM   #19
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So on a similar note, if you use an antifouler on your rear o2 sensor, then take it off at events, it won't have enough time to trip the CEL, right?

Seems like a cheap fix.
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Old 08-31-2007, 10:44 AM   #20
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Chris I might have misconstrued your post, but I'm still confused on the "usefulness" of the 2nd cat if it resides upstream of the 2nd O2 sensor.

Does the "3rd" cat even though it is behind the 02 sensor contribute to keeping the P0420 cel from pooping up? If so I just learned something brand new

TIA

^ I do agree w/ Phil that this whole emissions issue still isn't crystal clear (in my mind anyways) and appears to be somewhat of a moving target
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Old 08-31-2007, 10:58 AM   #21
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So on a similar note, if you use an antifouler on your rear o2 sensor, then take it off at events, it won't have enough time to trip the CEL, right?

Seems like a cheap fix.
Good question, that is possibly true. The anitifouler would keep the O2 sensors happy and the ECU in the ready state upon arrival to the event. The ECU may trip very quickly after you pull it or not. You will have to test it and see.

In my mind that is outside of the intent of the rules, but it could work and technically be legal.

Again, my intent was to show the WRX could be competitive and not throw P0420 codes, which in my mind complies with the way the rules have been clarified and meets the intent of the rules.

Last edited by FTD; 08-31-2007 at 11:14 AM. Reason: redundant...
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Old 08-31-2007, 11:13 AM   #22
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Chris I might have misconstrued your post, but I'm still confused on the "usefulness" of the 2nd cat if it resides upstream of the 2nd O2 sensor.

Does the "3rd" cat even though it is behind the 02 sensor contribute to keeping the P0420 cel from pooping up? If so I just learned something brand new

TIA

^ I do agree w/ Phil that this whole emissions issue still isn't crystal clear (in my mind anyways) and appears to be somewhat of a moving target
Sorry if I wasn't clear. Both cats live between the O2 sensors, in this order.

O2 sensor in the stock manifold ==> uppipe ==> Turbo ==> down pipe with high flow cat ==> mid pipe with high flow cat (O2 sensor after the cat) ==> cat back exhaust

I agree that it makes no sense to have cats down stream of the sensor.

If you look at most high flow down pipes you see the cat is in the location of the third cat with the O2 bung just downstream of that single cat. My Cobb down pipe was that way. The second cat and O2 bung in this system is in a similar orientation.
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Old 08-31-2007, 11:26 AM   #23
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Chris, I'm also a bit confused by your wording in an earlier post. Are your new downpipe and midpipes bolted in as purchased or did you have them modified to move the cats from their OTS positions before you installed them?

*edit, I may have found the answer to some of my confusion.

It appears that the components you purchased are the Xcceleration brand which use Random Technology catlytic converters. I had originally thought that the units you purchased were actually Random Technology pieces.

The pictures I found of Random Tech parts at http://www.wrxevolution.com/exhaustcbwrx.asp seem to have the 3rd cat in the same location as the stock cat and most every other aftermarket unit. Upon closer inspection of the Xcceleration 3rd cat pipe, it appears that IT has the 3rd cat located UPstream in the pipe, in a section that normally has a mounting bracket on every other (and stock) piece, with the O2 bung in a similar location to stock with a bend separating them.

Had you talked to the folks at Xcceleration about whether the components were available individually prior to your purchase? $870 is a fairly sizeable chunk of change for me to be dropping any time in the near future but I'd like to try their 3rd cat with my catless downpipe to see if it works. If not, I'd just have to figure their dp into the budget for before Nat'ls next year.

Last edited by Aaron B; 08-31-2007 at 11:41 AM.
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Old 08-31-2007, 11:32 AM   #24
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that makes more sense you've two cats "working for you" then- that certainly should do the trick
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Old 08-31-2007, 12:14 PM   #25
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Chris, I'm also a bit confused by your wording in an earlier post. Are your new downpipe and midpipes bolted in as purchased or did you have them modified to move the cats from their OTS positions before you installed them?

*edit, I may have found the answer to some of my confusion.

It appears that the components you purchased are the Xcceleration brand which use Random Technology catlytic converters. I had originally thought that the units you purchased were actually Random Technology pieces.

The pictures I found of Random Tech parts at http://www.wrxevolution.com/exhaustcbwrx.asp seem to have the 3rd cat in the same location as the stock cat and most every other aftermarket unit. Upon closer inspection of the Xcceleration 3rd cat pipe, it appears that IT has the 3rd cat located UPstream in the pipe, in a section that normally has a mounting bracket on every other (and stock) piece, with the O2 bung in a similar location to stock with a bend separating them.

Had you talked to the folks at Xcceleration about whether the components were available individually prior to your purchase? $870 is a fairly sizeable chunk of change for me to be dropping any time in the near future but I'd like to try their 3rd cat with my catless downpipe to see if it works. If not, I'd just have to figure their dp into the budget for before Nat'ls next year.
Yup the pictures on the site don't match what I recieved. So don't go by those. I should jack my car up and take some shots to clarify it for everyone.

The pipes are available individually, since they are built to order. I asked Sam about that and he said that he would sell them for 1/2 and 1/2. So one pipe costs half of the total, which would be $435+shipping. BTW, both pipes shipped for less than $30 to me.

One note on availability: Sam typically quotes 2 weeks for turn around, these are custom made by Random when you place your order. Sam was able to beat that for me, but plan ahead.

Do you know that the flange on the third cat will match up with your catless down pipe?
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