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Old 02-11-2005, 08:23 PM   #1
Killian Maynard
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Default 2005 WRX Cobb STG 2 lower RPM stutter

I'm running Cobbs AP stage 2 Cali with a MRT 3" TBE with only 1 cat in the 2nd cat position with res box removed and a K & N filter. During initial exceleration (between 1500-3500 rpms) the power delivery is a bit choppy untill 4500rpms where the engine begins to feel very smooth accompanied by a very strong pull up untill about 6K where power stops increasing. Also during the choopy phase (1500-3500) the intake suction (louder because no resbox) sounds inconsistent. Instead of a solid and consistent "sucking" noise it sounds as if the opening is changiong diamter so to speak making higher and lower pitches of sound. Like this whheeeeooooooowhheeeeoooooo instead of whhiiiiiiiissssssshhhhhh you know? I wish I had a recording, sorry.

So along with the choppy power band and funny intake sound the power just doesnt seem to be there like it should (I ran a access ECU stage 2 02 WRX with same mods and that felt faster than my 05?)

Any suggestions or help would be greatly appreciated. Thanks in advance.
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Old 02-11-2005, 09:22 PM   #2
yergi
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how is it that you have a cat in the "second position" if you have a TBE?
by this I think you are trying to speak of the downpipe cat?
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Old 02-11-2005, 09:53 PM   #3
Killian Maynard
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Quote:
Originally Posted by yergi
how is it that you have a cat in the "second position" if you have a TBE?
by this I think you are trying to speak of the downpipe cat?
Yes being that there are 3 cats in a stock system one in the upipe (1) and two in the stock TBE (2 and 3 respectively). The second cat in the stock TBE is right after the turbo outlet and the third cat is in the midpipe. My MRT TBE has 1 cat in the second cat location.
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Old 02-11-2005, 10:19 PM   #4
yergi
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why not just say DP cat then?
anyhows, Did you realize that COBB requierments for running stage 2 with the AP is to have NO DP cat?
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Old 02-12-2005, 12:34 AM   #5
Killian Maynard
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Sorry about the confusion, I guess I see the DP as having 2 cats and the second cat being what you consider the DP cat. Anyways, you may be right. I was hoping this setup would work ok because of the design of the outlet mouth and distance before the cat. I suppose running stage 1 might smooth things out. I will give that a try and see what happens.

Whats interesting about this is the comparrison between say the PPP which run with a downpipe almost exactly like I have. Prodrive still maages to get to similar power figures and spool up characteristics. I wonder what sort of tuning differences are employed be each.
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Old 02-17-2005, 03:08 AM   #6
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I didn't see the requirement from cobb to run catless in the dp. they do remark that their high flow cat test did not reduce the peak performance of the package compared to the catted dp.

i'm interested to see if your experiment going back to stage 1 will smooth things out.
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Old 02-17-2005, 04:53 AM   #7
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lmon50 is right. Cobbs tests with the catted dp and non catted dp show no differance in power. This is the only reason I bought a high flow catted Helix dp. It may be differante with a restrictave cat though. This may be why the stg2 only works with a full TBE. Most if not all companies TBE's are either catless or include high flow cats for cali. Your not running the wrong oct gas are you? How about any cel's?
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Old 02-17-2005, 10:42 AM   #8
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Quote:
Originally Posted by yergi
why not just say DP cat then?
anyhows, Did you realize that COBB requierments for running stage 2 with the AP is to have NO DP cat?
You're a moron, no offense. Do you even have an AccessPort? I think probably not.

You need an aftermarket DP to run Stage 2 that only has at most one cat.
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Old 02-17-2005, 10:43 AM   #9
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Quote:
Originally Posted by 03twrx
lmon50 is right. Cobbs tests with the catted dp and non catted dp show no differance in power. This is the only reason I bought a high flow catted Helix dp. It may be differante with a restrictave cat though. This may be why the stg2 only works with a full TBE. Most if not all companies TBE's are either catless or include high flow cats for cali. Your not running the wrong oct gas are you? How about any cel's?
Stage 2 works fine with just a DP. I ran it with a Stromung DP with the rest of the exhaust from there stock. Worked fine.
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Old 02-17-2005, 11:34 AM   #10
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Quote:
Originally Posted by subieworx
You're a moron, no offense. Do you even have an AccessPort? I think probably not.

You need an aftermarket DP to run Stage 2 that only has at most one cat.
come one bro, that was pretty uncalled for.
and yes, i beleive that the offense was intended.

in any case, yes, I do own an access port (street tuner on order)
the comment about the cat in the downpipe came from cobb's technical board where this question was asked in relation to the absolute minimum requierments to running stage 2. The question was answered with a statement from, I beleive trey, that the only real requierment was that the dp had to run without the cat.

link:
http://www.wrxforum.com/cgi-bin/ulti...585;p=2#000016

I think some people here may have some confusion with what a midpipe is, and what the downpipe is. the midpipe has a cat. you can leave that in place.

and subieworks: of course stage two works fine with just the downpipe,
It is the ONLY requirement (being that the stock cat restrictor is right there next to the turbo) not sure why you just contradicted yourself by agreeing with me?
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Old 02-17-2005, 11:42 AM   #11
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Quote:
Originally Posted by yergi
come one bro, that was pretty uncalled for.
and yes, i beleive that the offense was intended.

in any case, yes, I do own an access port (street tuner on order)
the comment about the cat in the downpipe came from cobb's technical board where this question was asked in relation to the absolute minimum requierments to running stage 2. The question was answered with a statement from, I beleive trey, that the only real requierment was that the dp had to run without the cat.

link:
http://www.wrxforum.com/cgi-bin/ulti...585;p=2#000016

I think some people here may have some confusion with what a midpipe is, and what the downpipe is. the midpipe has a cat. you can leave that in place.

and subieworks: of course stage two works fine with just the downpipe,
It is the ONLY requirement (being that the stock cat restrictor is right there next to the turbo) not sure why you just contradicted yourself by agreeing with me?
I guess the real problem is in the definition of the exhaust components. You define a DP as the first section of exhaust. I don't. Some poeple define the Mid pipe as the pipe that goes from the where a cat back would attach to the axle back. Some don't. I guess a lesson for us all is to not take info for granted and make sure we fully explain what we mean.
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Old 02-17-2005, 11:45 AM   #12
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now we are all on the same page, yes?
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