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Old 07-19-2006, 05:30 PM   #1
gould9184
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Default Stage II with Prodrive axleback? Has to be full 3"?

Hey guys...

I just purchased a 2006 Cobb Accessport for MT. Currently I am running a Prodrive axleback. For my DP, I wanted to either go with the 05 gutted downpipe and third cat pipes or just the 3rd cat gutted and a shorty DP such as a Bosal or Stromung.

So today, I called Cobb and asked if I could run the stock pipes gutted. Their tech support guy told me not to. So I asked if I can use a shorty DP and a gutted 3rd cat. He again said no. He said the exhaust needs to be a full 3".

I told him I am running a Prodrive axleback and stock intermediate pipe. I asked if I could still use these, and again he said no. This doesn't seem right to me. I know there are people out there running a Prodrive axleback with Stage II. Could any of you chime in here? Is he just being super cautious? Do I really need to have a full 3" exhaust?

What if I just ran the 91 octane map to be safe?

I have no idea what to do next, so any help is greatly appreciated.

(I don't have a lot of extra money now so I can't afford a Cobb TBE).
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Old 07-19-2006, 05:36 PM   #2
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eh im running stage 2 with a downpipe and stock catback and my car feels fine but I am abit worried about the EGT's. Also Im not making nearly as much boost as I was when I had a full turboback with no EM. Im only boosting max 14.5 and I should be hitting 15.2 in third/fourth gear. So if you dont have the money for a full turboback u can run it the way you have for awhile, just go full turboback when u can. Oh I just noticed you have a prodrive axleback, hell dude by the bosal intermediate pipe or that one from maddad so you can have a full turboback. shouldnt cost no more then $200.
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Old 07-19-2006, 05:54 PM   #3
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A. We actually field a lot of calls with people wanting the Stage 2 AccessECU because the dyno graph looks a lot better, but they do not have a turbo-back exhaust. Here is a diagram of the exhaust to help you visualize:




The Stage 2 was tuned on a car with a full turbo-back system. If you have pieced together a less than optimal combo of parts or those that were not designed to work together you may not get the full benefits of the Stage 2 AccessECU. Boost may not come on as quickly and the peak power may be down from those that have a well designed full turbo-back system. If you have replaced the first section (second cat or downpipe section) and nothing else, then the Stage 2 map is what we would recommend. Again the results will be far less than optimal, but it will control the boost better than the Stage 1. If you have replaced sections 2-4 (third cat, mid-pipe, and muffler section then you are still Stage 1. You managed to get all except the part that makes the most difference. Again, we want to reiterate that Stage 2 will only get the intended results with a well designed complete turbo-back.
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Old 07-19-2006, 06:04 PM   #4
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^^

Exactly. I read that also. So what they told me on the phone and what they say in their FAQ contradict themselves.
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Old 07-19-2006, 08:41 PM   #5
The Professor
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I have stage II with a TXs stealthback and a Prodrive axleback. No problems that I am aware of with it.
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Old 07-19-2006, 09:23 PM   #6
etirums
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I wouldn't run Stage II until you have the optimal components. Just my .02.

The guy on the phone was probably being cautious. Not overly cautious though, because we are altering the characteristics of our machines.
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Old 07-20-2006, 12:39 PM   #7
02slvrwgn
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I have been running the stock cat back with stage 2 and a 3" downpipe for two years now. I have no boost creep, am hitting 16.2 psi max, and my egt's at the manifold max at 820C for normal driving and track days. My car actually ran hotter on the highway at 130km/h using the stock map. The upside is my car is still quiet for the cops but it does not hold boost very well to redline. I have compared mine to a friends with the cobb tbe and his does hold more boost and he is only hitting 15.8. The drop in boost becomes noticible at about 5000 rpm and i am down about 1.2 psi at 7000 as compared to his car.
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Old 07-20-2006, 12:45 PM   #8
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I have a catless stealthback with the prodrive round-tip axleback. No problems here at all. I can run as much boost as a 3", have no boost creep, etc. I tune in street tuner and have compared a 3" to 2.5". There will be minimal differences in the two with anything but a turbo upgrade. When you start pushing 350awhp+ thats when the back pressure starts holding you back but with the VF39 or smaller by the time the exhaust gases hit the taper, they will have already cooled down which means they shrink and transition smoothly out the tailpipe.
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Old 07-20-2006, 05:19 PM   #9
johsti
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Quote:
Originally Posted by gould9184
So today, I called Cobb and asked if I could run the stock pipes gutted. Their tech support guy told me not to. So I asked if I can use a shorty DP and a gutted 3rd cat. He again said no. He said the exhaust needs to be a full 3".
It is very possible that he was trying to sell you a stage 2 package (full TBE and AP).

Sounds like a good salesman to me.

It says right on their website that the removal of the first cat after the turbo is all that's required to run the stage 2 map. You can go with any of your listed options and you'll be fine, and your car will feel much more powerful. You might be leaving a few hp on the table, but if your goal is to look stock and have a quiet car, then it's worth it. I would recommend getting a protune to make sure your car is running safely.
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Old 07-20-2006, 07:58 PM   #10
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^ Also adding to above post did the person from Cobb tell you that their DP tapers down to the stock donut gasket diameter.

I'm using a full DP with HFC and stock catback-no problems here too. In general the father away the restriction is from the turbo the better.
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Old 07-20-2006, 08:26 PM   #11
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Quote:
Originally Posted by johsti
It is very possible that he was trying to sell you a stage 2 package (full TBE and AP).

Sounds like a good salesman to me.

It says right on their website that the removal of the first cat after the turbo is all that's required to run the stage 2 map. You can go with any of your listed options and you'll be fine, and your car will feel much more powerful. You might be leaving a few hp on the table, but if your goal is to look stock and have a quiet car, then it's worth it. I would recommend getting a protune to make sure your car is running safely.
Yea, I was thinking the same thing. I thought it would be safe enough to do it, but this is my first brand new car and I wanted to be sure so I called. Problem is, I have a Prodrive axleback... I don't want to buy a 3" intermediate pipe, or I would have got a catback. My only option is a stealthback setup so I can still keep my Prodrive muffler if I'm going to go to a full 3". I don't know of any downpipe that is bellmouth, 3" and tapers down to 2.5" and mates up to the stock intermediate pipe... do you?


Quote:
Originally Posted by WRX03
^ Also adding to above post did the person from Cobb tell you that their DP tapers down to the stock donut gasket diameter.

I'm using a full DP with HFC and stock catback-no problems here too. In general the father away the restriction is from the turbo the better.
Yea, that figures. I knew it sounded a little odd they'd say it HAS to be 3". He made it sound like if it wasn't it was "extremely dangerous," and their own DP tapers down to stock diameter.

Anyway, I think I'm just going to stick with Stage 1 for now even though it's hardly any difference on the 06. If I knew of a DP that is bellmouth, 3" that tapers down to 2.5" and mated to the stock catback, I'd be set.

EDIT: I know they make aftermarket DP that will technically mate up to the stock catback, but I didn't want a 3" to 2.5" transition, because the possiblity of a leak.

Last edited by gould9184; 07-20-2006 at 08:33 PM.
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Old 07-20-2006, 10:56 PM   #12
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I have a prodrive muffler, a scoobysport shorty downpipe and am running Accessport stage2. I am running that on a '05 STi, I had the same setup on my '04 WRX and they both ran great!
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Old 07-21-2006, 01:50 AM   #13
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Quote:
Originally Posted by gould9184
Yea, I was thinking the same thing. I thought it would be safe enough to do it, but this is my first brand new car and I wanted to be sure so I called. Problem is, I have a Prodrive axleback... I don't want to buy a 3" intermediate pipe, or I would have got a catback. My only option is a stealthback setup so I can still keep my Prodrive muffler if I'm going to go to a full 3". I don't know of any downpipe that is bellmouth, 3" and tapers down to 2.5" and mates up to the stock intermediate pipe... do you?




Yea, that figures. I knew it sounded a little odd they'd say it HAS to be 3". He made it sound like if it wasn't it was "extremely dangerous," and their own DP tapers down to stock diameter.

Anyway, I think I'm just going to stick with Stage 1 for now even though it's hardly any difference on the 06. If I knew of a DP that is bellmouth, 3" that tapers down to 2.5" and mated to the stock catback, I'd be set.

EDIT: I know they make aftermarket DP that will technically mate up to the stock catback, but I didn't want a 3" to 2.5" transition, because the possiblity of a leak.
www.daddysscp.com or what ever maddad makes exactly what your looking for....it just costs alot.
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Old 07-21-2006, 01:51 AM   #14
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and going from 4 inch (bellmouth right?) to 3 inch to 2.5 inch to 3 inch is bad exhaust flow mojo. your gonna have so much danm turbulance dude its not even funny. Its best to have either full 2.5 inch or 3 inch all the way from your downpipe back.
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Old 07-21-2006, 03:36 AM   #15
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gould9184

Is there still Bigfoot sightings in Bedford?

Have you connected with the CIIC folks. http://www.phpbb88.com/ciic/index.php?mforum=ciic
If not talk to Dale (dbier) about your question. Nasioc is so big you get too many opinions.

Also there is a guy from Bedford on CIIC.

Last edited by WRX03; 07-21-2006 at 03:45 AM.
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Old 07-21-2006, 09:19 AM   #16
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Quote:
Originally Posted by Sypher
and going from 4 inch (bellmouth right?) to 3 inch to 2.5 inch to 3 inch is bad exhaust flow mojo. your gonna have so much danm turbulance dude its not even funny. Its best to have either full 2.5 inch or 3 inch all the way from your downpipe back.
Not true at all. If your sticking with the stock turbo which doesnt boost that much efficiently, then that actually makes for a very smooth transition. Gas is hottest as it exits the turbine so the large 4" bellmouth is accommodating for the expanded gases. As they travel further back down the exhaust stream the gases cool which cause the stream to contract. By the time it hits the rear section it has cooled enough to where the 2.5" taper still has plenty of room w/o causing any excessive back pressure or turbulance. If the turbo is upgraded then yes, the gases get hotter and need more room to decrease BP so a straight through design is a big benefit but anything less really doesnt need it.
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Old 07-21-2006, 11:41 AM   #17
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I am running stock gutted tbe and have used the OTS stg 2 map. Car ran perfectly fine. Boost came on quickly, all logs show EGTs to be actually quite low. I am now running a more aggressive TDC tuned map, and it spools even faster, feels more powerful throughout the rpm range, and again all logs show it is safe.

I don't see a gutted stock tbe to be holding me back significantly. On the tiny td04, it works well.
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Old 07-21-2006, 05:22 PM   #18
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I got a Perrin catless downpipe, stock mid-pipe, then Prodrive oval-tip. Runs great with a Stg. 2 flash.
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