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Old 06-28-2005, 04:03 PM   #1
anonymous_wolf
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Default Help! Just installed brullen header/hi-flow cat, but the car is slower!

Hi, just installed the brullen/hi-flow cat combination. i can feel that the low end has been improved, but the high end is slower!
in fact, i've done a little before and after 0-135km/h acceleration test, and the car after the header change is 1 seconds slower! (i'll post up the clip later).

before the header, i have a WRX apex'i N1 catback (tubing diameter of 2.55" midpipe and 3.05" axle back), now I have the RS N1 (tubing diameter of 2.35" all the way through).

during the installation, the mechanic was been very careless, he forget to put a gastek between the header and the cat and he forget to put my rear O2 sensor back! (so there's a hole in the car, literally) I drove like this for about 50kms. although the problem is now fixed, could it damage the cat and hense affect the performance?

any inputs would be greatly appreciated.

thanks
Kevin
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Last edited by anonymous_wolf; 06-28-2005 at 04:20 PM.
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Old 06-28-2005, 04:10 PM   #2
anonymous_wolf
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here's the clips:

after header back:
http://www.putfile.com/media.php?n=29031;29255;-059

before header back:
http://www.putfile.com/media.php?n=29031;29255;-2106

the only reason i can think of is the decrease in tubing diameter of the catback...but it still doesn't make sense. help!!!
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Old 06-28-2005, 04:17 PM   #3
impr25rs
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Did you remember to reset the ecu? Some times that will be enough. The rear O2 sensor just measures if the cat is doing its job, and that is about it.
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Old 06-28-2005, 04:19 PM   #4
anonymous_wolf
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yeah i reset the ECU already...
i have no CEL tho, the only good thing...
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Old 06-28-2005, 04:19 PM   #5
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try resetting your ECU, if it wasn't done after the install. I don't really understand your explanation of your pipe diameter(s). Everything now is 2.35"? If so, this should increase your performance even more rather than take away from it.




EDIT: whoops, I'm a little behind here, sorry for the double up
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Old 06-28-2005, 04:30 PM   #6
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i was just trying to think a reason that explains the lost in performance.
i heard larger piping diameter would be better for high end, so i was just guessing here.
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Old 06-28-2005, 06:24 PM   #7
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Here is something you may want to try. Remove the negative terminal from the battery. Step on the brake 4 or 5 times. Install the negative terminal at least 15 minutes later or more. (I know you mentioned that you reset the ECU, but bear with me). Start the car and let it idle for 10 to 15 minutes. Then go out for a drive. Go onto a highway or something that you can range the rpms from say 2000 - to redline in different gears. Do this for about 15 min. It will take the car a little while to adjust because you freed up a lot of airflow. By the way do you have an intake. If you have a lot of air going out and nothing going in it it may be a problem. I will listen to the vids when I am at a computer that has sound.

I don't think that it is the cat back because you have gone from something that was probably too big to a more resonable size. Just give the ECU time to adjust.
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Old 06-28-2005, 07:20 PM   #8
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thanks impr25rs
i'll try that later tonight

i did the ECU reset pretty much the same way as u mentioned except the highway run. so i should try that later.

and sorry that i forget to mention my intake, it's a PDM racing intake (same thing as ganz flow). the seller of the header has the same intake as mine, so intake shouldn't be an issue.

there shouldn't be any other leak, so i really donno what should i be looking for now.
i'm just a little worried about the cat, coz i drove the car with the rear O2 sensor been unpluged for quite a while.
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Old 06-28-2005, 07:35 PM   #9
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btw...
anybody know which O2 sensor is supposed to be extened when installing brullen headers?

i thought it's supposed to be the rear O2 sensor, but i think in my car the front O2 sensor is extended and it's connected to the plug in engine bay, and the wire of the rear O2 sensor was not adjusted, it just pluged onto the plug besides the tranny.

anybody have a picture of the stock cat on the car w/ the O2 sensors wired up~?
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Old 06-28-2005, 07:55 PM   #10
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a little sound clip i made earlier

http://www.putfile.com/media.php?n=P6280328
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Old 06-28-2005, 08:48 PM   #11
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Holy crap, I thought those were mph and my eyes almost popped out of my head.
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Old 06-28-2005, 10:16 PM   #12
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I suggest you do like impr25rs said and give it some time to adjust to the new airflow. You should also search around because I see threads like this all the time in these forums. Also, go to Unabomber's Manifesto and look up exhaust.
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Old 06-29-2005, 12:10 AM   #13
anonymous_wolf
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Garface, i wish its in mph too~

reseting the ECU as we speak~

i've searched a lot before I decided to buy the headers, and from all the threads i read, I should notice performance gain. that's why i'm so surprised when i found out there's not only no performance gain, but i've lost some. on the plus side, the regained low end is nice~ and i like the rumbling sound.
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Old 06-29-2005, 01:38 AM   #14
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Done ECU reset.
not a thing changed.

very tired of this, i'll get my mechanic to take a look of it later when i'm doing oil change. sigh
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Old 06-29-2005, 05:09 AM   #15
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right now my mechanic friend is thinking that that cat might be clotted by carbon, which explaines the restricted air flow, resulting in quieter than normal sound and slower high end acceleration. i'll take the cat out to see if it's clotted next week. what should i do to fix it if it's clotted?
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Old 06-29-2005, 07:18 AM   #16
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Could be something wrong with your setup, yeah. Otherwise, I think the ECU adjusts on its own after you drive a few hundred miles, without needing a reset.

=S2=
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Old 06-29-2005, 04:33 PM   #17
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yeah...i'll drive for another week and see if it gets better.
then i'll take the cat out when i'm doing my oil change next friday.
my bet is that there's a clot or something in the cat, but we'll see.
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Old 06-30-2005, 10:34 AM   #18
Kyle 2.5RS
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as far as i know, you don't want to mess with your front O2 sensor... it plays a roll in how rich or lean your fuel mixture is. The rear O2 sensor is essentially useless. It's for reading Cat efficiency, so people have used spacers to back it out a bit to help fight against the dreaded P0420 CEL.
I get the CEL with my brullen headers and hi-flow catback.
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Old 06-30-2005, 04:00 PM   #19
anonymous_wolf
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hum...so far I haven't got any CEL yet...
so which O2 sensor did you extended when you installed your brullen header?
the front or the rear?

I'm worried that the mechanic got my O2 sensors mixed up and connect them to the wrong plug or hole...
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Old 06-30-2005, 04:35 PM   #20
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You extend the rear one. If yours is not extended and you aren't getting a CEL then it could be that the cat is in fact "plugged". So, if it is plugged it isn't really "hi-flow" and therefore the O2 sensor wouldn't be seeing abnormal flow readings, as a plugged hi-flow is probably similar to or worse than a regular cat.

.02

Jared
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Old 06-30-2005, 04:38 PM   #21
impr25rs
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Quote:
Originally Posted by gtwagon941
You extend the rear one. If yours is not extended and you aren't getting a CEL then it could be that the cat is in fact "plugged". So, if it is plugged it isn't really "hi-flow" and therefore the O2 sensor wouldn't be seeing abnormal flow readings, as a plugged hi-flow is probably similar to or worse than a regular cat.

.02

Jared
Very true. I should have recognized that sooner since the posters car sounds quieter with the Brullens than stock.
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Old 06-30-2005, 04:49 PM   #22
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Quote:
Originally Posted by anonymous_wolf
yeah...i'll drive for another week and see if it gets better.
then i'll take the cat out when i'm doing my oil change next friday.
my bet is that there's a clot or something in the cat, but we'll see.

I think if you cat was clogged, you'd know it. It would not be a guessing game. You really haven't driven around long enough for the cat to have gotten clogged up in my opinion. I've recently driven around for weeks with an aftermarket cat, header and exhaust installed in my Subaru XT6. The mechanic did the EXACT same thing as yours did (forgot to install the O2 sensor). I was wondering why I heard a loud hissing sound driving by concrete walls and buildings but when looking at the exhaust itself, I couldn't find anything.

So, I installed an O2 sensor and the car drove fine. I went to the dyno shop and it performed no worse that it did previously with an O2 sensor installed.

I looked at the videos over and over again. Your Brullen header video's take off from the stop seemed slightly slower than the other run. Other than that, they both seemed to have increased speed about the same. Perhaps the top end loss is a perception instigated by the lower sounding exhaust.
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Old 07-01-2005, 04:54 AM   #23
anonymous_wolf
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thanks for the responses folks!

so, the cat is plugged, what can I do to save it?
i don't really want to spend any more money, just want to make it high flow again? any suggestions on what to do?

Kevin,
what would the car feels when it has a clotted cat? the cat was still good when it's in my friend's car, my car is noticeably quieter than his car with the same header back system. Also, I test drove his car before the swap, the car acceleration clearly increases when it revs above 4000rpm. That's why I think the cat is damaged during the installtion.

so even aftre driving around w/ a hole in the cat for a little while, there's no decrease in the performance of the car? (i mean after you've re-installed the O2 sensor, of course).

and yeah, I hit the redline and let it bounced a little bit in first gear when i was testing out the brullen header.

I timed it over and over again (hoping to prove myself wrong), acceleration from 0-135km/h is slower, I'm pretty sure of that.

on the plus side, the low end of the car has increased tremendously.
but i really really want to get my high end performance back. anybody know how to fix a plugged cat? other than getting a new one? lol

thanks again!

Last edited by anonymous_wolf; 07-01-2005 at 05:04 AM.
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Old 07-01-2005, 05:01 AM   #24
svek
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i do but its illegal
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Old 07-01-2005, 05:06 AM   #25
anonymous_wolf
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you meant your way of saving the clotted cat is illegal?

If you meant stealing a cat from another car I've thought about that already (a good friend of mine has a brullen header back system, hehe ), other than that, enlighten me please.
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