Welcome to the North American Subaru Impreza Owners Club Friday September 19, 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 10-08-2001, 04:33 PM   #1
FuZZyLoGiC
Scooby Specialist
 
Member#: 5970
Join Date: Apr 2001
Location: |_0|_|15\/1|_|_3 ,|<y
Vehicle:
2004 \/\/|2>< STi
Bp]V[ 97 |_||\|1<|-|1p2.0

Default twin dump vs single dump downpipe

OK single dump downpipe VS BPM Twin dump downpipe..What do you think?
* Registered users of the site do not see these ads.
FuZZyLoGiC is offline   Reply With Quote
Old 10-08-2001, 07:55 PM   #2
Naturally Aspirated
Scooby Newbie
 
Member#: 4734
Join Date: Mar 2001
Location: New Hampshire
Vehicle:
1997 Impreza OBS
Red

Default

I dont know about you but I would rather have a twin dump....in a single the waste gas hits a flat plate, bounces back up then exits through the downpipe. The BPM twin dump The waste gases exit through the secondary dump then back into the downpipe thus better flow which reduces turbo lag between gears and makes the turbo more efficient.


-Mike
Naturally Aspirated is offline   Reply With Quote
Old 10-08-2001, 08:20 PM   #3
FuZZyLoGiC
Scooby Specialist
 
Member#: 5970
Join Date: Apr 2001
Location: |_0|_|15\/1|_|_3 ,|<y
Vehicle:
2004 \/\/|2>< STi
Bp]V[ 97 |_||\|1<|-|1p2.0

Default

Ok so what if the whole down pipe was open. Both gases wouls exit out of the same down pipe opening. Would this be just as effective as a twin down pipe? Or would the turbulence from the two mixing make it less effective?
FuZZyLoGiC is offline   Reply With Quote
Old 10-08-2001, 08:41 PM   #4
Naturally Aspirated
Scooby Newbie
 
Member#: 4734
Join Date: Mar 2001
Location: New Hampshire
Vehicle:
1997 Impreza OBS
Red

Default

One large opening, that would be less effective like you said because of the turbulance and what not taking affect. I believe the twin dump would be the best way to go. I get to stare and drool over BPM's every day, they are the best craftsmanship I have EVER seen. I know gossamer_monster and Turbo4Me wouldn't give theres up for anything.


-Mike
Naturally Aspirated is offline   Reply With Quote
Old 10-08-2001, 08:44 PM   #5
FuZZyLoGiC
Scooby Specialist
 
Member#: 5970
Join Date: Apr 2001
Location: |_0|_|15\/1|_|_3 ,|<y
Vehicle:
2004 \/\/|2>< STi
Bp]V[ 97 |_||\|1<|-|1p2.0

Default

Hey yo thanks for the info. What type do thay have? Im looking to get an exhaust before the UniChip gets hear so I can tune it to the exhaust.
FuZZyLoGiC is offline   Reply With Quote
Old 10-08-2001, 09:26 PM   #6
TurboRex
Scooby Specialist
 
Member#: 8635
Join Date: Jul 2001
Location: Texas
Vehicle:
04 STI, 07 FXT

Default

If both are well designed, I doubt there is any difference IMHO.

Greg
TurboRex is offline   Reply With Quote
Old 10-09-2001, 01:39 AM   #7
nmyeti
Scooby Specialist
 
Member#: 4980
Join Date: Mar 2001
Location: Albuquerque, NM USA
Default

some day i may actually test this on my car, but i managed to run a pretty decent 13.2@101.3 with a single dump scoobysports system.

Makes you wonder doesn't it?

-Nathan
02 WRX
13.2@101.3 <--3600 feet above sea level.
nmyeti is offline   Reply With Quote
Old 10-09-2001, 03:07 AM   #8
XT6Wagon
Scooby Specialist
 
Member#: 524
Join Date: Nov 1999
Location: WA
Vehicle:
04 STi
White

Default

I'm sure a properly done twin pipe setup makes more power than a properly done single pipe setup. However on the stock WRX (except for the downpipe and back) I would guess that its worth MAYBE 1HP.
XT6Wagon is offline   Reply With Quote
Old 10-09-2001, 08:03 AM   #9
lbk16
Scooby Specialist
 
Member#: 4195
Join Date: Feb 2001
Chapter/Region: MWSOC
Location: Farmington Hills, Michigan
Vehicle:
2007 WRX Ltd. Wagon
2005 350Z

Default

Nathan-
Are you running the full SS turbo back?
lbk16 is offline   Reply With Quote
Old 10-09-2001, 09:16 AM   #10
Dori Dori
Scooby Specialist
 
Member#: 6780
Join Date: May 2001
Chapter/Region: South East
Location: South Florida
Vehicle:
1993 Nissan

Default

What would happen if you had a completely seperate, wastegate exhaust? I saw an Eclipse in SCC with this done. Someone told me if I do this, then fire will shoot out.

Sounds like fun to me.
Dori Dori is offline   Reply With Quote
Old 10-09-2001, 10:20 AM   #11
FuZZyLoGiC
Scooby Specialist
 
Member#: 5970
Join Date: Apr 2001
Location: |_0|_|15\/1|_|_3 ,|<y
Vehicle:
2004 \/\/|2>< STi
Bp]V[ 97 |_||\|1<|-|1p2.0

Default

Quote:
Originally posted by nmyeti
some day i may actually test this on my car, but i managed to run a pretty decent 13.2@101.3 with a single dump scoobysports system.

Makes you wonder doesn't it?

-Nathan
02 WRX
13.2@101.3 <--3600 feet above sea level.
What other mods do you have to add to your perfomance? Exhaust only?
FuZZyLoGiC is offline   Reply With Quote
Old 10-09-2001, 11:45 AM   #12
titsataki
Scooby Specialist
 
Member#: 4402
Join Date: Feb 2001
Chapter/Region: NESIC
Location: New Haven, Connecticut
Vehicle:
2009 Outback XT
DGM

Default

I think he has a Unichip as well...
and some other goodies...


Cheers

T.
titsataki is offline   Reply With Quote
Old 10-09-2001, 12:31 PM   #13
SCOOBYSHAG
Scooby Specialist
 
Member#: 358
Join Date: Oct 1999
Location: Dallas, TX
Vehicle:
2005 Xterra
Grey

Default

He has the stock turbo though...
SCOOBYSHAG is offline   Reply With Quote
Old 10-09-2001, 01:57 PM   #14
FuZZyLoGiC
Scooby Specialist
 
Member#: 5970
Join Date: Apr 2001
Location: |_0|_|15\/1|_|_3 ,|<y
Vehicle:
2004 \/\/|2>< STi
Bp]V[ 97 |_||\|1<|-|1p2.0

Default

Interesting. So with a better flowing exhaust would he dip into the 12s?
FuZZyLoGiC is offline   Reply With Quote
Old 10-09-2001, 02:09 PM   #15
gossamer_monster
Scooby Specialist
 
Member#: 3574
Join Date: Jan 2001
Chapter/Region: NESIC
Vehicle:
2002 WRX
Blase' Yellow----R.I.P.

Default

If he came down to sea level he'd be in the 12's

I don`t think his exhaust is going to flow much better without headers. He's catless right now so that is worth more then a single vs. twin dump.


Bill
gossamer_monster is offline   Reply With Quote
Old 10-09-2001, 02:27 PM   #16
4S-FED-WRX
Scooby Newbie
 
Member#: 9036
Join Date: Aug 2001
Vehicle:
2002 WRX
Blue

Default

If you really think about it there isnt gonna actually be much diff between a single or twin dump. If a twin dump comes together later in the down pipe you get the mixing (ie turbulence) later, which will still cause a back up in your exhaust gases. In a properly designed exhaust system whether it was a single dump or twin you should be able to get pretty close to laminar or ideal flow it is really just a matter of preference. The only way you make a big difference from a single is if your wastegate gets dumped to atmosphere.
4S-FED-WRX is offline   Reply With Quote
Old 10-09-2001, 02:43 PM   #17
solomrus
Scooby Newbie
 
Member#: 1767
Join Date: Jun 2000
Chapter/Region: MWSOC
Default it's not just the size of yer pipe...

it is how you use it!

there are two exchanges of energy at work in the turbine housing.

one is the mechanical exchange of the exhaust velocity hitting the blades of the turbine.

the second is the thermal exchange of the exhaust gas as it expands in the outlet/downpipe.

the first one is small, not really worth mentioning, as it does very little of the total work that the turbine requires. the second one is the one that needs some thought.

ok, you have *very* hot gasses, under pressure in the headers, and at a decent velocity. this hot gas is being constantly forced from the hottest area(combustion chamber) to the coolest area(outside the exhaust tip, behind the car).

what happens to a gas when it goes from a high pressure zone to a low pressure zone?

it expands

it cools

what happens to the hot, high pressure gasses behind this cooler, lower pressure zone?

they rush to fill it, therefore quickly raising velocity and losing pressure, and continuing the cycle.

ok, how does this apply to single and dual downpipes? here goes.

you have the main exhaust diameter immediately after the turbine outlet, and this is as large as possible to permit the thermal x-fer, and still maintain a reasonable velocity. what would happen if you were to introduce more hot gasses to this "ideal" environment that we have just created in the turbine outlet/downpipe?

for one, it would defeat the function of the expanding gasses removing themselves from the turbine, by hitting that zone with an instant blast of full-temp exhaust gas. this isn't great, but there could be worse things. like too small of a downpipe.

you know where i am going with this, don't you? eliminate this contamination by making the wastegate gas to take a different route away from the turbine than the main flow. voila, you have a double tube downpipe. ultimately, you would vent this somewhere up front for the best possible performance.

practically speaking, it is probably best to couple this back into the main exhaust system somewhere down the line(>12") where it will do less harm.

will this make more power by itself? no, probably not.

why bother?

a faster spooling turbo, more boost lower in the rpm range, and more torque baby. torque is what shoves your ace back in the seat. torque is what powers our little awd wonders away from the line with 4 tires scrabbling for traction. torque is king.

but, i digress.

pretty much any decent-flowing downpipe will assist in making the allmighty torque that we all lust for. the twin-downpipe for me is an ultimate solution to a not so horrific problem. given a large slow turbine that needs all the help it can get, i'll go double. other than that, give me a good scoobysport dp, and call it good. the bell-mouth method should be more than adequate, and quite satisfactory in the quick-spool department.

now, just get rid of those damn after-turbo cats...
solomrus is offline   Reply With Quote
Old 10-09-2001, 03:14 PM   #18
Dori Dori
Scooby Specialist
 
Member#: 6780
Join Date: May 2001
Chapter/Region: South East
Location: South Florida
Vehicle:
1993 Nissan

Default

So is it as simple as that? Just make a wastegate exhaust and you'll have better spool-up. Any side effects...will it kill the turbo? Can it be done on a stock turbo?
Dori Dori is offline   Reply With Quote
Old 10-09-2001, 03:25 PM   #19
solomrus
Scooby Newbie
 
Member#: 1767
Join Date: Jun 2000
Chapter/Region: MWSOC
Default

why not use a stock turbo?

it suits my purposes just fine. yeah, a nice ball-raced cartridge would help a lot, but i have no problem running the stock turbo for all it is worth.

it performs beautifully where it is intended to run. lower rpms, quick(well, for the most part) spool up, and a fairly low ceiling. mine will hold
13psi from 2nd to 5th from 3200rpm to about 6000 rpm where it will drop off.
solomrus is offline   Reply With Quote
Old 10-10-2001, 01:50 PM   #20
Obscure411
Scooby Specialist
 
Member#: 5719
Join Date: Apr 2001
Location: Morris County, NJ
Vehicle:
2008 Impreza 5-Door
Black

Default

Which begs the question (for me, anyways):

What if instead of my BPM GT System, I replaced it with a 3" single downpipe with NO wastegate tube (as in dumping to the atmosphere) and 3" pipe with no cats and an uppipe?

I currently have a Vishnu uppipe, BPM Downpipe + GT 3" exhaust with 1 3" high-flow cat.

Think I'd notice a decent spool increase? How much more noise? I can't imagine it adding much to top-end power, but perhaps slightly seeing as there is a bottleneck with the BPM downpipe design. Whaddaya all think?
Obscure411 is offline   Reply With Quote
Old 10-10-2001, 02:23 PM   #21
solomrus
Scooby Newbie
 
Member#: 1767
Join Date: Jun 2000
Chapter/Region: MWSOC
Default

let me ask this:

are you still running a stock turbo, and how quickly do you get to full boost?

and this:

how much noise can you tolerate?

i haven't personally heard an atmospheric w/g dump, but it can't be quiet. especially since the rest of the turbine outlet can vent thru that same hole as well. i imagine that it would sound much like a very bad exhaust leak.

i don't know about you, but i can't stand exhaust leaks, and the noise would be intolerable. i could see doing it on a race car, in fact, i guarantee that i would.

i think that going to a full 3" dp would be going too far. you have heard the adage that the best exhaust for a turbo car is no exhaust? well, you have now... there are reasons why you don't want to go too big. the main one is a loss of velocity. things slow down when the pipe gets too big. now, a 3" d/p that dumped shortly after the turbine would be ok... the gas has to efficiently move thru the system to get out of the tailpipe.

i would stick with what you have. a good, un-restricted d/p, external w/g dump, and 3" exhaust. that should be more than you would need, even with one of the higher-flowing turbos that are available. i wouldn't go larger on the down pipe.

let me know where your boost comes in full. that will give me a better idea of where to look next.

i would guess that with that exhaust, you also are running a better intake system?

--r
solomrus is offline   Reply With Quote
Old 10-10-2001, 03:07 PM   #22
TurboRex
Scooby Specialist
 
Member#: 8635
Join Date: Jul 2001
Location: Texas
Vehicle:
04 STI, 07 FXT

Default

Well, you might be able to see 1 hp difference between a single and dual dump downpipe....and again I say might. Even if you do, the cat and the muffler will make any gains moot. Even if just a muffler, it will slow the flow up enough to also make this issue moot in my opinion. Now if you guys are not running a midpipe or muffler section, then that is another issue. Even so, I can't see any measurable gains in the 1/4 mile.

Greg
TurboRex 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
Twin plate vs. single plate clutch mtcs Newbies & FAQs 2 03-15-2010 01:19 PM
twin scroll vs single acssa Built Motor Discussion 15 11-19-2009 03:20 AM
Twin plate vs. single plate clutch? w321shark Newbies & FAQs 4 08-18-2008 08:52 PM
single dump Downpipe + Wastegate wRx14pSi Factory 2.0L Turbo Powertrain 0 06-17-2002 03:25 PM
Downpipe - twin dump vs single WRXterminate Factory 2.0L Turbo Powertrain 11 05-20-2002 12:05 PM


All times are GMT -4. The time now is 04:17 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.