Welcome to the North American Subaru Impreza Owners Club Monday July 28, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Factory 2.0L Turbo Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 05-21-2001, 08:50 PM   #1
djerickd
Scooby Guru
 
Member#: 3782
Join Date: Jan 2001
Chapter/Region: South East
Location: Tampa B*tch!
Vehicle:
02 WRX WFC#040
Clean on 19's

Post What style downpipe is better? (Twin-dump or Single)

As in Twin-Dump like BPM's design:
<IMG SRC="http://home.att.net/~boxer4racing/Bpm/gtexhaustsystem.jpg" border=0>

Or a big Single dump that covers both the wategate and turbo like APS:
<IMG SRC="http://www.airpowersystems.com.au/wrx/housing.jpg" border=0>

Which design works better?
* Registered users of the site do not see these ads.
djerickd is offline   Reply With Quote
Old 05-22-2001, 08:04 AM   #2
mrbell
Scooby Specialist
 
Member#: 1871
Join Date: Jul 2000
Location: Salt Lake City, UT
Vehicle:
2000 Impreza 2.5RS
Blue Ridge Pearl

Post

I can't say I know for sure, tho, I'd think that the single inlet would have more area to flow thru which would be good...
but, on the other hand, the twin inlet might flow smoother...
that clear things up? ;-)
mrbell is offline   Reply With Quote
Old 05-22-2001, 08:14 AM   #3
Diz
Scooby Specialist
 
Member#: 874
Join Date: Feb 2000
Chapter/Region: RMIC
Location: Colorado Mountains
Vehicle:
2003 Honda S2000
2004 Mazdaspeed MX-5

Talking

I just had this explained to me this weekend. The twin dump provides a separation for the boost bled by the wastegate. The theory is to eliminate any disturbance to the flow of exhaust gases. Hence, a better flowing exhaust will decrease spool up time.
Diz is offline   Reply With Quote
Old 05-22-2001, 08:17 AM   #4
outback motorsports
Scooby Newbie
 
Member#: 4084
Join Date: Feb 2001
Location: buena park, ca.
Post

we sell the down pipe flanges for $20.2.5 in.with a 1 in.hole for the waste-gate. see ya steve
outback motorsports is offline   Reply With Quote
Old 05-22-2001, 09:11 AM   #5
stimpy
Homicidal Maniac
Moderator
 
Member#: 1612
Join Date: Jun 2000
Location: Austin, TX
Vehicle:
2008 STI

Post

For the 1st 8" off the back of the turbo, you want as little disturbance as possible. Any disturbance can give excessive back pressure and rob the engine of power. This will also hurt turbo spool up. By smoothing out your exhaust flow, the turbo will boost harder and faster.

Just for the record, in my DIY turbo setup, I am using the Outback Motorsports twin-dump downpipe flange.

-Jon
stimpy is offline   Reply With Quote
Old 05-22-2001, 10:56 AM   #6
jjameson
Scooby Specialist
 
Member#: 4986
Join Date: Mar 2001
Chapter/Region: NESIC
Location: Back frm Ireland Fallbrook, Ca
Vehicle:
2002 BlzYel JDMSTiv7
GRP 08 FXT

Post

Don't forget about a hybrid design like MRT's.
<IMG SRC="http://albums.photopoint.com/j/View?u=246497&a=12990426&p=48971495&f=0" border=0>

I just installed my MRT 3" turbo back. I have some pics of the system and the install to put up as well as my thoughts on the system vs. others. I will be posting all this soon.
jjameson is offline   Reply With Quote
Old 05-22-2001, 11:20 AM   #7
iceweazel
Scooby Specialist
 
Member#: 6816
Join Date: May 2001
Chapter/Region: MWSOC
Location: Cowlumbus, OH
Vehicle:
01 yeller wrx
triumph tiger,klr,cb900f

Post

Theoretically a twin dump with totally seperate lines the entire length ^_^

However in RL, twin with a couple of inches
seperate. On stock turbo cars this
really doesn't have much effect with most
stock turbos due to them running out of
gas at higher RPMs where the disturbance
would be felt most. On cars with larger
turbo wheels and good fill, it can be
felt immeadiately.

iw
iceweazel is offline   Reply With Quote
Old 05-22-2001, 03:33 PM   #8
BPM
Scooby Newbie
 
Member#: 542
Join Date: Nov 1999
Location: Worldwide
Post

Answering this question is one of the key understandings of design of downpipes.

Letís consider facts firstly....

A large Turbo exit suffers from the following shortcomings.

Gas turbulence as the gases meet thus affecting natural gas flow.

Generalizing that all turbos have the same cavity depth.

Generalizing that the turbo size does not affect the turbo flange design.

All the above are cost cutting measures to have a generic downpipe.

Moving onto Prodrive...

They are generally viewed as the benchmark most Subaru aftermarket companies strive for....

The utilize a Twin Dump Design with a larger diameter wastegate pipe than the BPM variant for the simple, fact that have better clearances on the WRC car.

There is a further superior method which allows superior exhausts/wastegate flow by not letting the wastegate pipe join the primary thus venting to atmosphere...This bypasses al the R and D required on "when to join the primary to secondary pipe"

Having the separator plate in the flange *exactly* match the turbo is extremely important. It is the accuracy of fit to the turbo that makes it work. The cavity depth of a TD 04 series and a VF series varies quite drastically.
The separator plate that keeps the wastegate charge from interrupting the flow of the main turbine exhaust flow must be made specifically for each turbo so that it keeps ALL the wastegate gases away from the turbine gases.

Minimum turbulence = maximum flow.

This points to exacting standards, and an accurate fit. This is the only true way to keep the wastegate gas turbulence from upsetting the flow from the turbo with an integral wastegate turbo.

The diameter of this wastegate pipe has been chosen through extensive R and D sessions and we will soon release the X Series System for race applications only which will showcase the latest technology in Twin Dump Design.

The BPM TD Downpipes are also HPC COATED for performance gains, elimination of thermal fatigue/oxidation and superior gas flow.


Hope this helps


Greg Nikolettos
ICQ # 85002510
Australia Ph 1300 850 BPM
International + 61 7 3272 8885
Facsimile + 61 7 3272 8045
bpm@bpmsports.com www.bpmsports.com
BPM is offline   Reply With Quote
Old 05-22-2001, 05:13 PM   #9
djerickd
Scooby Guru
 
Member#: 3782
Join Date: Jan 2001
Chapter/Region: South East
Location: Tampa B*tch!
Vehicle:
02 WRX WFC#040
Clean on 19's

Post

Well I guess that answers it! Thanks!
djerickd is offline   Reply With Quote
Old 05-22-2001, 05:21 PM   #10
gimpster
Scooby Specialist
 
Member#: 2295
Join Date: Sep 2000
Chapter/Region: NWIC
Location: Seattle
Post

When do you plan to release this X-series downpipe and what are it's features over the one you currently offer?
gimpster is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
what downpipe is better for my wrx 03 ??? gocho Pre-2002 Factory Turbo Powertrain 2 05-22-2007 03:44 PM
zilla td06-20g, *DOWNPIPE* twin dump or bellmouth? WRXout Factory 2.5L Turbo Powertrain 2 09-04-2005 04:38 PM
What E.M is better the UTEC or AEM EMS STi_Guy04 Engine Management & Tuning 12 01-18-2005 12:55 PM
twin dump or bellmouth? wannaimpreza Factory 2.0L Turbo Powertrain 7 11-12-2002 11:31 PM
any difference with twin dump or bellmouth turbo flange?? showcasewrx Newbies & FAQs 0 10-14-2002 12:21 PM


All times are GMT -4. The time now is 07:07 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.