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Old 10-14-2012, 10:37 PM   #1
mcgti6
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**CEL after catless downpipe install, HELP ME**

Hi guys,

I'm a noob. but i installed a catless downpipe on my 2010 gti dsg and now have a CEL. i've been reading that spacers between the o2 sensor and the downpipe will "trick" the car into thinkin there is a cat there and the CEL will go away... is this true?

i am also wondering if me going stage 2 now is REQUIRED due to new downpipe...? (50-50 of ppl saying yes and no on other forums for other cars)

i read online that cars will run lean if they aren't stage 2 tuned...true/false?

or will the car run lean because the o2 sensor sees that there is no cat converter anymore so the ecu will change the AFR itself?

and im guessing running lean will screw up major components, but how long would it take to do so (incase i wanted to stay stock for $$$ reasons now) ?


some of my friends say that the CEL is just indicating that the cat isnt there anymore so no worries (i already know that cuz i installed the dp) its just a light on the dash and thats all, but is the CEL relaying the msg to ECU and having it run leaner???


IF ANYBODY CAN ANSWER SOME OF THESE QUESTIONS I'D APPRECIATE IT.

sorry i'm so "ignant" bout this stuff. i've never modded a car b4
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Old 10-14-2012, 10:43 PM   #2
kurupt_hawaiian
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Just get the stage II tune, it will delete the CEL. Nothing to worry about!
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Old 10-14-2012, 11:12 PM   #3
yoffer
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The downstream o2 sensor wont change your afr's. The reason it throws a CEL is because the exhaust gases are traveling through at a much higher rate because of the freeflowing design and the o2 sensor is unable to get a reading. The o2 "spacer" is used to bascially "sniff" the exhaust gases so the o2 sensor can read it (this is the assumption i am under) ive heard some o2 spacers still throw a CEL but ive heard great reviews from the 42dd o2 spacer working very well. Or you can get flashed stg2 if you choose, but i heard that going stg2 is just to get rid of the CEL on the dash, it doesnt actually give you more power. But if you have the option too, you might as well get the flash anyway.
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Old 10-14-2012, 11:16 PM   #4
mcgti6
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well i work at a machine shop, so i could probably have one of our toolmakers make me a threaded elbow or some sorta spacer for it.

the thread size for the sensor a "M18 mm x 1.5mm"?
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Old 10-14-2012, 11:22 PM   #5
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Why not just buy one that you know that works? Not all the spacers work as some will say and just welding a elbow together isnt garranteed to do the trick.
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Old 10-15-2012, 03:56 AM   #6
mcgti6
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trust me, it'll be better than just something welded together. lol plus, i could make one faster than it'd take to order one, and i've seen the 42dd spacer. i could easily replicate that.

but APR says stage 2 tune gives you more power...? i dont get what u mean when u say it doesnt
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Old 10-15-2012, 03:58 AM   #7
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Quote:
Originally Posted by mcgti6 View Post
trust me, it'll be better than just something welded together. lol plus, i could make one faster than it'd take to order one, and i've seen the 42dd spacer. i could easily replicate that.

but APR says stage 2 tune gives you more power...? i dont get what u mean when u say it doesnt
not to mention it's high key expensive

does the job well though i hear!
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Old 10-15-2012, 08:02 AM   #8
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Originally Posted by mcgti6 View Post
trust me, it'll be better than just something welded together. lol plus, i could make one faster than it'd take to order one, and i've seen the 42dd spacer. i could easily replicate that.

but APR says stage 2 tune gives you more power...? i dont get what u mean when u say it doesnt
Is the more power coming from the tune or because you installed a downpipe? Once you go "stg2" you do get more power because you added a downpipe lol. Unless Apr UPS the boost in their stg2 file.

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Old 10-15-2012, 08:23 AM   #9
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Quote:
Originally Posted by yoffer View Post
The downstream o2 sensor wont change your afr's. The reason it throws a CEL is because the exhaust gases are traveling through at a much higher rate because of the freeflowing design and the o2 sensor is unable to get a reading. The o2 "spacer" is used to bascially "sniff" the exhaust gases so the o2 sensor can read it (this is the assumption i am under) ive heard some o2 spacers still throw a CEL but ive heard great reviews from the 42dd o2 spacer working very well. Or you can get flashed stg2 if you choose, but i heard that going stg2 is just to get rid of the CEL on the dash, it doesnt actually give you more power. But if you have the option too, you might as well get the flash anyway.
The reson for the CEL is not because the exhaust moves to fast to read, that's completely false. The front 02 reads the air fuel ratio and relays it back to the engine constantly so it can adjust the fueling constantly. The rear 02 checks the exhaust again to make sure the catalytic converter burned up what the engine didn't. It monitors tha cat effeciency. You get a check engine light because you removed/downgraded the cat from OEM and its boy as clean and efficient anymore. The point of the spacer is so only a small bit of the exhaust makes it to the rear sensor so it's tricked it into thinking a small sample is clean exhaust.
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Old 10-15-2012, 09:35 AM   #10
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The reson for the CEL is not because the exhaust moves to fast to read, that's completely false. The front 02 reads the air fuel ratio and relays it back to the engine constantly so it can adjust the fueling constantly. The rear 02 checks the exhaust again to make sure the catalytic converter burned up what the engine didn't. It monitors tha cat effeciency. You get a check engine light because you removed/downgraded the cat from OEM and its boy as clean and efficient anymore. The point of the spacer is so only a small bit of the exhaust makes it to the rear sensor so it's tricked it into thinking a small sample is clean exhaust.
As in "sniffing" the exhaust?
If you read my post i said thats the assumption i was under as to why it throws a code. But basically everything you just said is exactly what i said already.
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Last edited by yoffer; 10-15-2012 at 09:42 AM.
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Old 10-15-2012, 10:00 AM   #11
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Also, which engine do you have? CBFA/CCTA? CBFA will be more difficult to get right. I'm struggling with that CEL now too (CBFA). I tried a regular o2 spacer you get from autozone, definitely didn't work (170 miles). Tried 034's beefy o2 spacers (two this time), and they completely flopped after 60 miles. I think they pulled my o2 sensor too far from the exhaust flow because I was getting codes saying they were not getting readings.

I think my next step is either rai j spacer (adjustable jets) or a tune & prepare for a clutch.
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Old 10-15-2012, 10:13 AM   #12
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As in "sniffing" the exhaust?
If you read my post i said thats the assumption i was under as to why it throws a code. But basically everything you just said is exactly what i said already.
No it isn't. The check engine light has NOTHING to do with the exhaust traveling at a higher rate. It monitors the oxygen content of the exhaust to see how clean it is, not the speed at which it moves.
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Old 10-15-2012, 11:50 PM   #13
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dbest,

i see what your saying about the oxygen sensor. now, does the 2nd sensor seeing that the cat isn't there anymore send any kinda signal to the ecu to adjust the afr? or is the mixture set in stone now cuz i have stage 2 tune... (btw, i went and got the stage 2 apr flash today & omg "i'm lovin' it")

the CEL is still showing up even after the stg 2 tune. the dealer said that he sells a faultcode erase that will take care of it but advised i get it w/ the 4 other programs during a sale to save some money.

but he said the CEL is just a light now, its not really affecting my car now. what do u guys think? does that sound fishy?
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Old 10-15-2012, 11:52 PM   #14
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Doesnt apr have a 'test pipe file' and a non test pipe file? Or are they both suppose to get rid of the cel?
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