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Old 08-26-2009, 11:37 PM   #1
gbwrx
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Default STU combinations that work without CEL

Okay, I have been searching and reading...reading and searching on this and am tired of looking around.

I have a 2006 STi that I have been running in AS for the last couple of years and am ready for something else. So, I am thinking about prepping the car for STU.

I was wondering if people could post up what exhaust combinations they have been using that work without throwing a CEL. I know there is a bunch of posts on this but many of them are dated and some have contradicting info. Mainly, I would like to know of some of the combinations that have been working for people for awhile now.

This is what I was planning on doing. Port and polish factory header, shorty downpipe with divorced wastegate, mid pipe with hi-flow cat, straight pipe, and pro tune. I just don't want to buy X brand of downpipe or whatever and find out that it throws a CEL.

Thanks in advance.
Shawn Gebbia
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Last edited by gbwrx; 08-26-2009 at 11:46 PM.
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Old 08-27-2009, 08:51 AM   #2
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I haven't paid attention to what works in ST in awhile but this my help you. I think I remember helix working for the sti.

http://forums.nasioc.com/forums/show...ht=stx+exhaust
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Old 08-27-2009, 09:54 AM   #3
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Thanks for the link. But I have read over that thread. Some people posted about something that worked but then came back later and posted that they ended up throwing a cel. I guess what I am mainly interested in is anyone that has had success with what they have for awhile now.
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Old 08-27-2009, 11:36 AM   #4
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"work" for how long?
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Old 08-27-2009, 12:07 PM   #5
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im running a helix on my 07 wrx it took about 25 miles to throw a code for cat inefficiency with my Stu map
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Old 08-27-2009, 01:34 PM   #6
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No. 1 priority: Make sure the 02 bung is BEHIND your cat.

Me? No CELs in 10,000 miles with a catless shorty downpipe, MadDad hi-flow and MadDad cat back.
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Old 08-27-2009, 02:34 PM   #7
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Cool, thanks. What dp you running?
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Old 08-27-2009, 04:05 PM   #8
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At lot of us have been running the Stromung divorced shorty with a maddad catted mid-pipe without CEL trouble for a while now.

I know you can get a twin-catted solution that has worked in every single case it was tested in, but it's pricey.
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Old 08-27-2009, 04:26 PM   #9
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I've got the Cobb TBE with high flow cat. I probably ran it for a couple 1000 miles last summer without a CEL. I also came up for emissions and took it to the EPA on the STU tune. So now I have an official EPA document stating that I am legal.

/Rant On
And this is what ticks me off about the stupid emissions rules. What part of what the OP is going through is consistent with "a natural competition outlet for auto enthusiasts using affordable sports cars and sedans equipped with common suspension, engine, and appearance modifications which are fully legal and compatible with street use anywhere in the country"????? (emphasis mine) This emissions BS was a stupid clarification that only served to make competitors wonder if they were truly legal. Luckily it seems like most competitors accept it for what it is and no silly protests have been filed.
/Rant Off

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Old 08-27-2009, 09:03 PM   #10
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Well, if you get right down to it, with the clarification, you never know if you are legal or not. You could be at one event, but not at another. You could go almost a whole season being legal, then the light pops on one time, and then you are not legal.

The '08 champ won on the same DP that threw CELs all day long on my car. I don't take that as he's blocking the codes though, I take it as his car is subtly different from mine and that is why the rule fails. His passes, mine failed, all on the same DP. Go figure

So far, we're lucky nobody in ST*, except for the STAC, gives a crap about that rule.
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Old 08-27-2009, 09:19 PM   #11
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Quote:
Originally Posted by gbwrx View Post
Cool, thanks. What dp you running?
Dunno. Perrin maybe. It's divorced.

I think the point is: make an honest effort, make sure the 02 bung is behind a functioning high-flow cat, don't block the codes and call it a day.


It's a dumb rule and hopefully everyone knows it's a dumb rule by now. Upsetting the status quo is a hornet's nest with good points on both sides of the argument. Stirring it up wouldn't change anything for the good for either side.
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Old 08-27-2009, 09:50 PM   #12
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I agree that it is a very stupid rule clarification. When it happened I was running in AS and was pretty happy I had just sold my old WRX that was running in STX. My car would have been "illegal" per the clarification. Actually everyone in my region running a Subaru in ST* that year was then illegal.

At this point since I am wanting to get back into a ST* class....I just want to try to make a conscious effort to be legal before the fact of buying new parts for the car.

It sounds like what I had been wanting to do should be alright.

Edit---Thanks again for everyone's replies. Soon I won't feel like the outsider in a Subaru in AS with Honda S2000's all around me.
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Old 09-05-2009, 11:52 PM   #13
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Quote:
Originally Posted by mccanixx View Post
I haven't paid attention to what works in ST in awhile but this my help you. I think I remember helix working for the sti.

http://forums.nasioc.com/forums/show...ht=stx+exhaust
I am running the Helix and it has worked for me for 20k miles with no CEL.

-Colin
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Old 09-06-2009, 12:03 AM   #14
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Yeah, that's the one. I used to run a Helix too. I couldn't drive 100 miles without a CEL with it. However, mine seems to like my Stromung/Maddad combo just fine. Go figure.

Like I said, it's stupid. I long for the days when a part was illegal because of what it was or what it did, not what code it 'might' trip.
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Old 09-06-2009, 11:07 AM   #15
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Quote:
Originally Posted by Splash View Post
At lot of us have been running the Stromung divorced shorty with a maddad catted mid-pipe without CEL trouble for a while now.

I know you can get a twin-catted solution that has worked in every single case it was tested in, but it's pricey.
I had a two Magnaflow high flow cat downpipe built for ~$400 (thanks TurboXS). They don't have to be pricey. Anyhoo, no CELs for me.
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Old 09-06-2009, 12:31 PM   #16
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Yeah, my backup plan was to buy a cheap catless DP and have 2 of those 100-cell cats they're sellin over on evolutionm welded into it before the O2 bung. Luckily, so far, I haven't needed that plan.

But then, I suppose that is my point. Anytime someone says "no CELs for me", it needs to be qualified with "so far". Nobody can say that they will not get a cat inefficiency CEL. They can bet on it, they can be confident in it, but they can't say they won't get one. It can happen at any point. Everyone without a CEL is legal, but only for the time being. Unlike static compression or boost tables, it doesn't need you to change something in order to all of a sudden be not legal anymore.

I have often thought we've been going about this the wrong way. Instead of finding cats that don't trip the stock OBD system, we need to find O2 sensors that send voltage in the ranges the OBD system expects with the cats we have. Since the O2 is replaceable as well, this could be a cheaper route.

Last edited by Splash; 09-06-2009 at 12:48 PM.
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Old 09-07-2009, 08:22 AM   #17
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Quote:
Originally Posted by gbwrx View Post
Port and polish factory header, shorty downpipe with divorced wastegate, mid pipe with hi-flow cat, straight pipe, and pro tune. I just don't want to buy X brand of downpipe or whatever and find out that it throws a CEL.
Just going to throw this out there for what its worth.

Depending on your state and local ordinances, running a straight pipe will fail you at inspection. NC is one of those places. Im fairly sure TN is one of those places as well. While you wont fail for emissions equipment per se, most states have noise pollution ordinances in place.

Moreover, most sites these days have noise requirements. My car with a straight pipe would have never met them. Not even close.

So, while you may want to be "emissions legal" for STU, running a straight pipe will likely take you back to square one.
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Old 09-07-2009, 03:40 PM   #18
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We have noise restrictions at some of our sites. I think it is 96 dbs. I currently run AS and have the straight pipe on. I don't come close to the limit now. Hopefully once install the dp I won't go over. But if I do I can just look at an exhaust.

Noise definately is something to consider. Thanks for throwing that out there.
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Old 09-12-2009, 02:17 PM   #19
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For the first time, they enforced emissions this year at Nats. I was hoping to find more details on the test, but they used propane to test for rear O2 sensor defeats.

[EDIT]
Quote:
Originally Posted by pinkertonpunk View Post
They were injecting propane gas into our intakes with a scanner hooked up to see if when they turned on the propane that our oxygen sensors and fuel trim would change. It would make the engine stutter when it was turned on. They were basically testing to make sure we all had functioning oxygen sensors and we all did.

Jake was in an STI though, just so you know! That would have been more amazing in a WRX though. Congrats to all the Subarus though, too bad it was finally the Evo's year in STU.

-Colin

Last edited by stimpy; 09-12-2009 at 02:22 PM.
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Old 09-12-2009, 05:53 PM   #20
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So there you go, buy the Helix, it is cheap as hell and works for STU!

-Colin
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Old 09-12-2009, 08:21 PM   #21
gbwrx
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Yep. If I would have been patient and waited for Nats I would have an answer.

Thanks again for everyones input.
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Old 09-12-2009, 10:27 PM   #22
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At first glance, the high flow cat on the Helix and Invidia DP seem far from the required distance specified in the STU rules. Did I miss something? Or is this wildly different for the GD vs GR STi?

Relevant rule:

4) Be used in the same location(s) as the OE converter(s).
This does allow for high performance replacements, provided
they meet all restrictions herein.
STX, STU:
Any high flow catalytic converter(s) are allowed, but must attach
within six inches of the original unit. Multiple catalytic converters
may be replaced by a single unit. The inlet of the single
replacement converter may be located no further downstream
than 6"
along the piping flow path from the original exit of the
final OE converter
.

So from the bolded section here I'm assuming anything further upstream on the pipe like the Helix and Invidia is STU compliant.

Last edited by nostra; 09-12-2009 at 10:38 PM.
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Old 09-12-2009, 10:59 PM   #23
gbwrx
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Hmm. I was thinking it only mentioned....."The inlet of the single
replacement converter may be located no further downstream
than 6" along the piping flow path from the original exit of the
final OE converter."

I didn't realize it also mentioned...."Any high flow catalytic converter(s) are allowed, but must attach
within six inches of the original unit."

With it mentioning both the Helix may not be legal. Reading the rules makes me so confused.
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Old 09-12-2009, 11:03 PM   #24
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Actually after reading the rule again.....it states..."The inlet of the single
replacement converter may be located no further downstream
than 6" along the piping flow path from the original exit of the
final OE converter."

So I read this as if you are using a single replacement instead of the douple replacement then the cat can not be further than 6" downstream. It doesn't mention anything about being upstream and how far that it can be there. So the Helix would be legal.
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