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Old 07-21-2010, 12:52 AM   #1
thesniperz
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Default UEL headers , CEL

i've been researching for different UEL header setups for my07 2.5i and was noticing that people are getting CELs and some dont.

Is there a good setup to avoid getting CEL?
if you're not getting a CEL on your 2.5i, can you post your setup?


thanks!
-JC



**my bad, if this has been asked a million times, i swear i searched!
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Old 07-21-2010, 09:52 AM   #2
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only way to be sure of no MIL is to have it tuned
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Old 07-21-2010, 10:57 AM   #3
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For a lot of people it's only because they new UEL headers they bought have thinner walls so they let more heat escape and the CEL the car is throwing is because temp. at the catalytic converter are too low and not high enough for maximum efficiency. If that's the CEL that's being thrown either powder coating or wrapping the headers will prevent this.
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Old 07-21-2010, 02:17 PM   #4
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Ceramic coating won't prevent the P0420 DTC. Been there, tried that. Wrapping them will prevent it under some environmental conditions, but not all of them.
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Old 07-21-2010, 04:57 PM   #5
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Quote:
Originally Posted by williaty View Post
Ceramic coating won't prevent the P0420 DTC. Been there, tried that. Wrapping them will prevent it under some environmental conditions, but not all of them.
So you agree that it's a heat issue? Interesting... What about cat placement? I wonder if the guys getting this code have the cat back far enough that it's not getting hot enough.

I'd have to assume that wrap and having the cat immediately follow the header would be the best setup for these newer cars (07+, right?)
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Old 07-21-2010, 07:37 PM   #6
thesniperz
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so wrapping the headers fixes the CEL issue?

I'd have to assume that wrap and having the cat immediately follow the header would be the best setup for these newer cars
is this true?
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Old 07-21-2010, 09:09 PM   #7
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That last part was supposed to be posted as a question. I was making an assumption, and waiting for someone to confirm or deny that.

I've heard it's the '07+ cars that are finicky with the o2 sensors, so that was another question in there.
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Old 07-21-2010, 09:39 PM   #8
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I think it's a head and flow issue. Controlling the heat does seem to help the situation. However, there's no guarantee that wrapping the header will prevent the DTC.
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Old 07-21-2010, 11:19 PM   #9
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yeah ive got my headers coated, wrapped and then coated again and i got a CEL two days ago and its starting to go on and off!
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Old 07-21-2010, 11:57 PM   #10
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hmmm...
so is the CEL just randomly coming off? do you guys have to reset the ECU to take it off or does it go away on its own?
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Old 07-22-2010, 09:12 AM   #11
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Quote:
Originally Posted by Travisty View Post
So you agree that it's a heat issue? Interesting... What about cat placement? I wonder if the guys getting this code have the cat back far enough that it's not getting hot enough.

I'd have to assume that wrap and having the cat immediately follow the header would be the best setup for these newer cars (07+, right?)
I have a thread explaining all this placement, heat as it pertains to optimal exhaust gas composition. Basically if you plot efficiency, temp, and distance from the engine on a graph you will see that the ECU (2006+) like that cat close and HOT! (900F+) this is why the ECu delays readings for the first few miles and also why that air pump pumps in O2 to help fire and get them toasty for cleaner air.

The is also why you should have UEL custom made for 2006+ cars to have the cat as close to the stock location as possible.
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Old 07-22-2010, 11:44 AM   #12
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@GEE-OTTO - so basically, wrapping the headers and having the cat as close to the stock location as possible will prevent the CEL?
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Old 07-22-2010, 01:35 PM   #13
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Quote:
Originally Posted by thesniperz View Post
@GEE-OTTO - so basically, wrapping the headers and having the cat as close to the stock location as possible will prevent the CEL?
The only thing that will prevent the DTC is leaving the entire exhaust alone.

Once you start modding the exhaust there is no miracle cure. You can do some things, such as wrapping the exhaust, that make it more or less likely that you'll keep the ECU happy. There are no guarantees.
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Old 07-22-2010, 02:19 PM   #14
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ok..
burble with CEL or no burble, no CEL... right?
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Old 07-22-2010, 02:20 PM   #15
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Or you could get a top-quality EL header and disable the DTC in the ECU and have both power and no DTC. Best of all worlds.
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Old 07-22-2010, 04:34 PM   #16
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but i want the rumble though..
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Old 07-22-2010, 04:37 PM   #17
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Quote:
Originally Posted by thesniperz View Post
but i want the rumble though..
going to go with the carbon hood, oil-slick tires, and slam it too?

Seriously, rumble is just rice that you're not going to get teased about by most people.

If you want the sound that bad, put up with the DTC.
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Old 07-22-2010, 05:01 PM   #18
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Quote:
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going to go with the carbon hood, oil-slick tires, and slam it too?

Seriously, rumble is just rice that you're not going to get teased about by most people.

If you want the sound that bad, put up with the DTC.
yeah! carbon hood, big picnic table spoilers, oil-slick sh**, slammed in the ground like no one else have done it before, put about 50 stickers for more HP.. all those things!!............ NOT!!!!

damn people these days..

<---- subie newbie, but not ricer.
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Old 07-23-2010, 09:54 AM   #19
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Quote:
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@GEE-OTTO - so basically, wrapping the headers and having the cat as close to the stock location as possible will prevent the CEL?
Wrapping is more a function of sound insulation (the dreaded TICK ) and ambient temperature control. However when making a custom setup the more "stock" like you make it the better chance your ECU can't tell the difference.

however you can get this tuned out the user kero had this done for his 2.5i with UEL setup and he has no MIL's
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Old 07-23-2010, 10:06 AM   #20
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Quote:
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but i want the rumble though..

Hey youre not alone in that desire I see both sides EL and UEL this is owner choice. The stock is a great EL header but the other ones work well and give you some bottom end grunt. I think Willitay has a graph showing the gains of the EL over the UEL over stock I want to say there was 5-10 hp gains at high RPMs EL vs UEL but I personally don't drive in the 5K RPm range regularly nor do I consider my 2008 Legacy 2.5i a "perfomance" vehicle it is a sporty one but no way a performance car so I can live with the boxer rumble and without 7 extra ponies up top but some are performance driven and opt for the EL to squeeze ever HP they can out of their EJ251/3.

Again owner choice and the EL still comes with the MIL like the UEL
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Old 07-23-2010, 10:15 AM   #21
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^ thanks! i could live without extra hp as well and get the rumble.
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Old 07-23-2010, 10:44 AM   #22
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Quote:
Originally Posted by thesniperz View Post
^ thanks! i could live without extra hp as well and get the rumble.
If you drag race or race or w/e then EL it up all day but i tour so my money goes to things like solid 22mm F/R sway bars and chassis stiffening and H techs and Sat radio modules
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Old 07-23-2010, 10:58 AM   #23
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nah, i dont drag or any kind of race.. just dd all day..
thanks for the tips!
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Old 07-23-2010, 12:04 PM   #24
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I had gotten the P0420 cat deficiency cel with my UELs and trackpipe, I had a local tuner edit the ECU MAP to remove that code all together, has never come back up since and it allowed me to pass inspection now and forever, granted they don't check under the car.
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Old 07-23-2010, 12:18 PM   #25
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It is true that the only way to permanently clear the DTC is to eliminate it via reflash. That's how the track pipe boys do it. Welding a cat in a near stock location is next to impossible because the stock cat is actually integrated into the exhaust manifold. I have a high flow cat in mine, but I'm not running any o2 sensors. I had my tuner take out the codes, and I have not had any issues at all.
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