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Old 10-24-2007, 06:24 AM   #1
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Default fabing down pipe, need input...

the last step (finally) in my build is to fabricate the down pipe. ive got a t25 with the five bolt backend. i can either run the gasses from the waste gate and the impeller seperately or combine them at the back of the turbo. ive heard that running the gasses seperately for 22" is supposed to be beneficial, i dont remeber why. or i can just have them collect right behind the turbo.

if i ran a seperated setup, do you think that it would affect the readings from the o2 (this is assuming the o2 is in the main streem)?

any input would be great.
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Old 10-24-2007, 07:11 AM   #2
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The O2 sensor would need to be down stream, Below the point that the waste gate gasses enter the main stream of the down pipe.
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Old 10-24-2007, 08:04 AM   #3
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If you have the time, patience, and clearance for separated, go for it. Otherwise, a bell mouthed DP has worked for people for years.
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Old 10-24-2007, 09:24 AM   #4
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Quote:
Originally Posted by Atlanta93LE View Post
If you have the time, patience, and clearance for separated, go for it. Otherwise, a bell mouthed DP has worked for people for years.
Agreed. Divored DP's are a PITA. I do bellmouthed on my stuff, but divorced on customer's if they want to pay for it

Not sure about the O2 sensor question but I don't really see why it'd be bad to have it in the main pipe. On the MSM Divorced WG DP I did, I put the upper O2 sensor bung in the main pipe up close to the turbo (by the factory location) and the owner has not had any problems.
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Old 10-24-2007, 09:30 AM   #5
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there's still plenty of exhaust running through the turbo at full boost so your o2 reading should be fine. That's the way I'm doing it. Thinking of re-introducing the WG gasses to the main exhaust though. Sound does get annoying. Either that or add a separate small muffler for the WG dump
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Old 10-24-2007, 09:40 AM   #6
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a mixture is a mixture, doesn't matter where it's being routed.
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Old 10-24-2007, 12:42 PM   #7
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According to corkys book, he mentions that the main advantage to having a divorced downpipe is the reduction in turbulence caused by the exhaust gases coming out from the turbo and wastegate at different rates.

I am sure that theres merit to that, but not enough to make a drastic difference in performance.
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Old 10-24-2007, 01:17 PM   #8
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Here is Corky's explanation:
http://www.bellengineering.net/Pages/comments.html

Put the O2 sensor on the main pipe in a relatively stock location. The major benefit to a S/G pipe? Low end torque.
Stephanie
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Old 10-24-2007, 01:19 PM   #9
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Quote:
Originally Posted by Stephanie Turner View Post
Here is Corky's explanation:
http://www.bellengineering.net/Pages/comments.html

Put the O2 sensor on the main pipe in a relatively stock location. The major benefit to a S/G pipe? Low end torque.
Stephanie
Dyno proof?
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Old 10-24-2007, 01:26 PM   #10
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None on an actual dyno. All butt dyno's confirm though.

The person who was supposed to do a comparison never came thru.
Stephanie
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Old 10-24-2007, 01:47 PM   #11
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I'm not going to comment on the sensitivity of your butt (dyno).
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Old 10-25-2007, 02:48 AM   #12
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Quote:
Originally Posted by Stephanie Turner View Post

The person who was supposed to do a comparison never came thru.
Stephanie
oh BURN
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Old 10-26-2007, 12:17 AM   #13
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As Atlanta93LE stated, if you have the room and patience, go for the divorced WG. I built my own DP with divorced wastegate and have no complaints.

http://www.mazdas247.com/forum/attac...hmentid=111862
http://www.mazdas247.com/forum/attac...hmentid=111863
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