Welcome to the North American Subaru Impreza Owners Club Tuesday May 31, 2016
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo)

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 02-28-2003, 02:43 PM   #1
krillz
Scooby Specialist
 
Member#: 29874
Join Date: Nov 2002
Location: new york
Vehicle:
2002 wrx
mblackp

Default 3 inch downpipe into 2.5 inch exhaust?

I wanna keep a 2.5 inch exhaust becuse i beleive scoobysports theory that it retains quicker spool up capabilities and would only hinder performance in well over 300 flywheel hp applications

but should/can i get a 3 inch downpipe into a 2.5 inch exhaust?

i was looking at fastwrx's buschur exhausts, in which you can build a complete turboback for under $900

or should i just stick with the turboxs becuase although its bigger i can get a similar price.
* Registered users of the site do not see these ads.
krillz is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 02-28-2003, 04:17 PM   #2
David Buschur
Former Vendor
 
Member#: 24301
Join Date: Sep 2002
Location: Wakeman, Ohio
Vehicle:
2006 WRX 345hp/345tq
White

Default

Funny I would be the one to come across this since you are considering our exhaust:0)

Anyway, whatever you do DO NOT run a 3" downpipe into a 2.5" catback. We have done that and dyno tested the results, let's just say IT SUCKS. So if anything stick with the full 2.5" system.

BTW, our full stainless steel 2.5" system with the offroad pipe is only $625 and weighs in at less than 24 pounds for the entire system. If you want the highflow cat just add $150.

Take care,
David Buschur is offline   Reply With Quote
Old 02-28-2003, 04:53 PM   #3
romoranger
Scooby Specialist
 
Member#: 14701
Join Date: Jan 2002
Location: scottsdale, az
Vehicle:
94 camaro
big cam/heads/slicks

Default

you CAN do it if you want, but then again, i have a 3" downpipe connected to the stock cat back which is something like 2.25"
romoranger is offline   Reply With Quote
Old 02-28-2003, 05:34 PM   #4
krillz
Scooby Specialist
 
Member#: 29874
Join Date: Nov 2002
Location: new york
Vehicle:
2002 wrx
mblackp

Default

David, thanks for the response! Whats the dyno difference between the 2.5 and the 3?

I mean, is the three inch substantially better?
krillz is offline   Reply With Quote
Old 02-28-2003, 05:41 PM   #5
KenpoKev
Scooby Newbie
 
Member#: 32564
Join Date: Feb 2003
Location: Genoa, Nevada
Vehicle:
2002 WRX
Silver

Default

I would also like to see the results of from dyno testing of a 3-2.5 vs. 3-3 even. I currently have a 3-2.5 set-up (not by my choice) and was told by several sources that the effects would be minute unless I did extensive modifications to the motor.

If you have evidence otherwise, I'm all in favor of changing out my cat-back to a 3" and you'll get the first crack at selling me a 3" unit!

Please be sure to provide details of the engine set-up (upgrades) along with the pull charts.

Thanks!
Kev
KenpoKev is offline   Reply With Quote
Old 02-28-2003, 10:55 PM   #6
atf78
Scooby Specialist
 
Member#: 9017
Join Date: Aug 2001
Chapter/Region: Tri-State
Location: Sewell, NJ
Vehicle:
2011 WRX 5dr
405whp 385wtq

Default

BUMP this because I'm interested in those dyno results as well. Been kicking around the idea of modifying my Apexi WS exhaust. It starts at 2.5" and expands to 3" at the axleback. I may have a shop fab a custom midpipe to where it expands to 3" and have a full 3" system.
atf78 is offline   Reply With Quote
Old 02-28-2003, 11:28 PM   #7
scurry
Scooby Newbie
 
Member#: 13543
Join Date: Dec 2001
Location: Southern Maryland
Vehicle:
2002 WRX
Blue

Default

Quote:
Anyway, whatever you do DO NOT run a 3" downpipe into a 2.5" catback. We have done that and dyno tested the results, let's just say IT SUCKS. So if anything stick with the full 2.5" system.
Wow! I guess someone should contact Scoobysport about this, looks like they have no idea on what they are doing....

Shawn
scurry is offline   Reply With Quote
Old 03-01-2003, 12:41 AM   #8
koloumb
Scooby Newbie
 
Member#: 28268
Join Date: Oct 2002
Chapter/Region: NWIC
Location: Oregon
Vehicle:
2002 WRX Sedan
WRB

Default

The only disadvantage [ie: Suckage factor] I can think of are the mating surfaces/sizes between the 3" outlet of the DP and the 2.5" inlet of the cat back.

I noticed this problem mating up a Perrin DP with a Tanabe Hyper Super Medalion [2.75"] exhaust. It [Perrin DP] doesn't have the important outlet flang that the stock downpipe has that helps seal the gap between the dp and the catback exhaust. I had to use some McGiver skills to ensure a proper seal using the dp o-ring gasket [which I expect is probably failing more and more each time I lead foot the gas].

_0wen_
koloumb is offline   Reply With Quote
Old 03-01-2003, 01:28 AM   #9
krillz
Scooby Specialist
 
Member#: 29874
Join Date: Nov 2002
Location: new york
Vehicle:
2002 wrx
mblackp

Default

Quote:
Originally posted by scurry
Wow! I guess someone should contact Scoobysport about this, looks like they have no idea on what they are doing....

Shawn
i thin k mr buschur is saying that with HIS product it wasnt benefitial. if you want a scooobysport than get a scoobysport, if you wanna try something new from someone you can speak directly with then try out buschur...

and as far as i know, buschur has been tuning turbo allwheel drive vehicles just as long as scoobysport
krillz is offline   Reply With Quote
Old 03-01-2003, 04:16 AM   #10
jsmonet
Scooby Specialist
 
Member#: 14190
Join Date: Jan 2002
Location: so. cali
Vehicle:
2005 STi
white

Default

seriously, everyone has their own way of doing things. sometimes a pipe isn't just a pipe i guess.

i too would like to know if buschur has done full 3" vs. 3"->2.5" vs. 2.5" dynos.

i'm currently running 3" -> 2.25" (pde -> stock), and about to go to 3"->3+" (pde->blitz nur spec touring)
jsmonet is offline   Reply With Quote
Old 03-01-2003, 12:26 PM   #11
jrexilius
Scooby Newbie
 
Member#: 21713
Join Date: Jul 2002
Location: evanston, il
Vehicle:
2002 wrx sedan
black

Default

Quote:
Originally posted by David Buschur
Funny I would be the one to come across this since you are considering our exhaust:0)

Anyway, whatever you do DO NOT run a 3" downpipe into a 2.5" catback. We have done that and dyno tested the results, let's just say IT SUCKS. So if anything stick with the full 2.5" system.

BTW, our full stainless steel 2.5" system with the offroad pipe is only $625 and weighs in at less than 24 pounds for the entire system. If you want the highflow cat just add $150.

Take care,
who is we? you got a url?
jrexilius is offline   Reply With Quote
Old 03-01-2003, 08:41 PM   #12
ChristophWRX
Scooby Specialist
 
Member#: 19009
Join Date: May 2002
Chapter/Region: SCIC
Location: Orange County
Vehicle:
2005 M3/WRX by clark
silver/white

Post exhausted

just installed my turbo xs downpipe, 3 inch race pipe with 2.5 inch hks axleback. plan on going full three inch when i get a bigger turbo, i will dyno it soon, should be fine..
oh, PDE up pipe is a great peace..installed all this last night, i love the sound and performance...
chris
ChristophWRX is offline   Reply With Quote
Old 03-03-2003, 12:36 PM   #13
Rally Performance
Vendor
 
Member#: 16588
Join Date: Mar 2002
Location: www.rallyperformance.com
Default Hi David

Hi all - noticed this thread

David, let me say that I respect your products, and have followed your tuning ever since we were running a Galant VR-4...

I do have to differ with the statement that 3" into 2.5 sucks. In some cases it may.... but let me explain what we do that is known to be very effective.

Krillz - by what you wrote, I'm guessing that you are assuming our downpipe is 2.5"... it is actually larger, and what you are after may just be our pipe, or one like it.

The ScoobySport is actually a 5.5" wide bellmouth downpipe, tapering down to 3". The system then later tapers to 2.5" to go to the next pipe in line. The beauty of this is that it gives you flexibility... but has developed a pretty legendary reputation for area under the torque curve. It doesn't suck.

Dave, perhaps you dynoed a 3" only downpipe, like the HKS, that doesnt have the same flow properties as ours (or other good bellmouths like TXS).

In any case, I wanted to make the point that we vary the diameter, and that the ScoobySport is not just a 2.5.

Regards,
Ken Cole
Rally Performance /
ScoobySport North Amercia
Rally Performance is offline   Reply With Quote
Old 03-03-2003, 12:41 PM   #14
krillz
Scooby Specialist
 
Member#: 29874
Join Date: Nov 2002
Location: new york
Vehicle:
2002 wrx
mblackp

Default

thanks for the very informative reply! i was directing that at scurry who was comparing burschurs downpipe to yours
krillz is offline   Reply With Quote
Old 03-03-2003, 01:45 PM   #15
driggity
Scooby Specialist
 
Member#: 7453
Join Date: Jun 2001
Chapter/Region: BAIC
Location: Bay Area, CA
Vehicle:
2014 Scion FR-S
Hot Lava

Default

I'm pretty sure that Buschur was talking about a connecting a 3" system to a 2.5" system without having any kind of tapering going on. Theres going to be a big difference in a system that tapers to 2.5" and one that goes directly from 3" to 2.5". Thats obviously going to be bad for airflow.
driggity is offline   Reply With Quote
Old 03-04-2003, 09:50 AM   #16
Mark B.
Scooby Newbie
 
Member#: 9848
Join Date: Sep 2001
Location: Palmdale CA
Vehicle:
2002 WRX
Platinum Silver

Default

krillz

You can also try this as a way to stay with a 2.5 pipe, I have been very happy with this set-up.

http://www.geocities.com/skoshiracing/Efficient.html

Cheers
Mark B. 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
Tial Exhaust Housing and 2.5 inch Vs 3 inch outlet Jamaal Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo) 9 10-27-2009 03:26 AM
fs: WBR 3 inch to 2.5 inch exhaust adapter $40 silverGDB SCIC Private Classifieds 10 04-09-2009 10:44 PM
2.25 Inch exhaust vs 2.5 inch exhaust kghost Normally Aspirated Powertrain 3 02-27-2007 04:51 PM
3 inch downpipe with 2.5 inch catback? Larsony Newbies & FAQs 13 09-22-2005 08:07 PM
Power differences between 3 inch and 2.5 inch exhaust? pha qed Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 8 04-13-2004 05:14 PM

All times are GMT -4. The time now is 11:58 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2016 Axivo Inc.
Copyright ©1999 - 2016, North American Subaru Impreza Owners Club, Inc.