Welcome to the North American Subaru Impreza Owners Club Thursday July 10, 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 General > Proven Power Bragging

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 05-09-2014, 06:06 PM   #1
Cobb Tuning
NASIOC Vendor
 
Member#: 4803
Join Date: Mar 2001
Location: Austin, DFW, Portland, SOCAL
Default Exhaust Gas Backpressure testing - IWG vs. EWG - COBB Tuning Surgeline on 2010 WRX

Event: R&D Dyno Testing
Location: COBB Tuning Surgeline
Ambient Temp: Mild - 60's
Elevation: Sea Level
Weather: Mild

Car: 2010 WRX - COBB Tuning R&D Vehicle - "Ketchup"
Tuner: Lance Lucas
Dyno Info: Mustang AWD-500-SE
Transmission: OEM 2009 5MT
Gear: 3rd

Target Boost: Wastegate Pressure (0% WGDC)
Engine/Power Modifications: Stage2+SF (COBB Turboback Exhaust, COBB SF Intake/Airbox System). COBB 44mm EWG Kit w/atmospheric dump installed for EWG tests.
Tuning: COBB AccessPORT with v331 OTS maps (Stage2+SF 91 Octane with WGDC set to 0%)


Hey guys,

After finishing up a pretty big round of pending OTS updates for the 2009-2014 WRX, we decided to put our R&D WRX through some more rigorous testing regarding common modifications. Much like most customer cars, when equipped with full Stage2+Intake hardware, our car suffers from very severe boost creep. Even when it's not bad enough to cause a P0244 CEL, the fuel injectors are run right to the ragged edge from 5500 RPM to redline. Anyways...meet Ketchup the 2010 WRX. Look closely at the front passenger side of the bumper and you'll see the pressure measurement hose extending out and towards the dyno cart:




One of the more interesting but rarely-covered topics in turbocharged tuning is that of exhaust gas back pressure (EGBP), or EMAP (exhaust manifold absolute pressure). On a Subaru, this is generally measured somewhere between the exhaust manifold collector and the turbocharger itself.

Positive pressure in the exhaust manifold (a positive pressure differential between turbine inlet and outlet) is required to drive the turbocharger but also represents a trade-off against an engine's efficiency level and ability to displace air. The less pressure the engine has working against it when the exhaust valves are open, the happier the engine tends to be. In a perfect world, we would be able to create boost w/o restricting the engine at all. Physics don't allow this unfortunately so we work to balance them. In racing scenarios, aiming for an EGBP/Boost pressure ratio of 2.0 or lower is a very general rule of thumb. Just some general statements here and the topic is well-covered in a variety of tuning and automotive/SAE texts.

The goal of these tests were to test our kit for its relative ability to eliminate boost creep on Stage2 & Stage2+Intake on the 2009-2014 WRX. More importantly, in our previous testing, we found that EMAP was *very* high on the 2009-2014 WRX at high RPM, which is a contributor to their strong tendency for detonation when fuel quality is not great. Knowing this, we wanted to compare EMAP on both the stock IWG and the EWG configuration. We then calculated the relative pressure ratio between exhaust and intake manifold with each configuration.

All of these runs were completed with the boost control system disabled (wastegate duty cycle set to cap of 0%) to demonstrate the boost system's performance on the IWG and then the EWG. The EWG spring pressure chosen for this test was .9 bar.

This data was collected using a stock manifold that has been tapped at the collector for the AEM Exhaust Back Pressure kit with sensor logging via the Mustang Dyno PowerDyne controller/software.

Stage2+SF hardware vs. Stage2+SF+EWG hardware, both at wastegate boost levels:





** Clarification: "EMAP" is show as PSI relative to ambient atmosphere in this scenario, where the goal is comparing intake manifold boost (IMAP - Baro) against exhaust manifold pressure (EMAP - Baro).

Summation:

- On the IWG, EGBP/Boost ratios exceed 2.0 at high RPM. In other words, to produce ~12.5psi of boost at redline, pressure in the exhaust manifold is ~26psi with the stock internal wastegate.

- On the EWG, EGBP/Boost ratios are 1.5-1.6 at high RPM. In other words, to produce ~12.5psi of boost at redline, pressure in the exhaust manifold is ~19.5psi with the COBB 44mm EWG kit with atmospheric dump.

- EWG with atmospheric dump: muy bueno for power and efficiency purposes!


In the future we hope to extend this testing out to include recirculated EWG kits, upgraded turbos, different turbines and/or A/R housings with the same compressors, etc. Thanks for reading along!

Cheers

Lance
* Registered users of the site do not see these ads.

Last edited by Cobb Tuning; 05-09-2014 at 10:34 PM.
Cobb Tuning is online now   Reply With Quote
Old 05-09-2014, 06:17 PM   #2
CPU GUY
Scooby Newbie
 
Member#: 203347
Join Date: Feb 2009
Chapter/Region: NWIC
Location: Portland, OR
Vehicle:
07 STi
Blue

Default

Nice work! very beneficial information.
CPU GUY is offline   Reply With Quote
Old 05-09-2014, 06:20 PM   #3
Clark Turner
NASIOC Vendor
 
Member#: 178047
Join Date: Apr 2008
Chapter/Region: SWIC
Location: AZ/Vegas
Vehicle:
02 WRX STI Spec C
Black

Default

I have been testing exhaust backpressure for many years. Some of the aftermarket hybrid turbos are well over 3 to 1. I used a SS line hooked to the EGT probe spot and then to a vac line and a gauge.

Hence, The EWG makes more power which is what I have been saying for years while others say its not possible.

Nice write up Lance!

C
Clark Turner is offline   Reply With Quote
Old 05-09-2014, 06:21 PM   #4
arghx7
Scooby Specialist
 
Member#: 232940
Join Date: Dec 2009
Location: cold
Default

In my experience, between 200 and 250kPa gauge pressure at the turbine inlet is common backpressure on stock exhausts for most modern turbo cars. Once you get over 230-250kPa, your residual gas fraction increases (more knock sensitivity), and so does your pumping work. The other thing that can happen with this high backpressure (regarding hybrid turbos for example) is that it's a lot for your exhaust valves to work against. It can cause valve float.

Do you have cylinder pressure indication (maybe spark plug pressure transducer)? Can you show pumping mean effective pressure and chart it's relationship to turbine inlet pressure? That's what you really need to figure out: how much of your indicated torque is being wasted on pumping.
arghx7 is offline   Reply With Quote
Old 05-09-2014, 07:00 PM   #5
Innovative Tuning
NASIOC Vendor
 
Member#: 67958
Join Date: Aug 2004
Chapter/Region: Tri-State
Location: www.InnovativeTuning.com
Vehicle:
MY96 Time Attack
and 06 STI daily

Default

I love it when you talk data to me Lance.
Innovative Tuning is offline   Reply With Quote
Old 05-09-2014, 11:23 PM   #6
STirish
Scooby Newbie
 
Member#: 71515
Join Date: Sep 2004
Chapter/Region: TXIC
Vehicle:
'06 STi
Aspen White

Default

Nice work as usual, Sir.
STirish is offline   Reply With Quote
Old 05-10-2014, 12:02 AM   #7
GrpB
Scooby Newbie
 
Member#: 101976
Join Date: Dec 2005
Default

Quote:
Originally Posted by arghx7 View Post
can cause valve float.
I have heard this before but in reality have never seen it in several variants of modern gas turbo direct injected small displacement I4's, even if the -all crank referenced- (pressure at the exh port) x (valve face area-stem diameter) is greater than (in cylinder pressure) x (valve face area), based on running valve lash measured at the cam base circle relative to tappet (lash would go to zero if valve was being forced open). The actual exh valve lash loss through the entire exh cam event due to engine load/resulting temperature differentials, which has the effect of greatly retarding the mechanical valve closing, is of a much greater concern for combustion effects, specifically the risk of misfire due to reversion and resulting high residual.

Comparing crank referenced cylinder pressure, intake plenum pressure, intake port pressure, exh port pressure, turbine inlet pressure and post turbine pressure - all overlaid, the (actual) exh valve closing, intake valve opening, and exh manifold (pre turbine inlet) design are the big knobs to turn. The turbine's wants for high turbine inlet pressure vs. the engine's want for low pressure at the exh ports during each cylinder blowdown could mostly(except for misfire events) be balanced pretty effectively with cam timing and exh manifold design. Assuming it's a fun car and emissions requirements are not a deliverable. But I'm obviously a hardware guy, not a cal guy, so easy for me to say.
GrpB is offline   Reply With Quote
Old 05-10-2014, 12:13 AM   #8
NowDatsG
Scooby Newbie
 
Member#: 364933
Join Date: Aug 2013
Location: Owings mills, Md
Vehicle:
08 Wrx sedan
Silver

Default

This Is a good read at least to me. Makes me want to move over to ewg on my 08 even more.
NowDatsG is offline   Reply With Quote
Old 05-10-2014, 12:27 AM   #9
arghx7
Scooby Specialist
 
Member#: 232940
Join Date: Dec 2009
Location: cold
Default

^^ When you start to look at it one dimensionally like that, (simple calculation using crank angle resolved values and geometric parameter) it's certainly possible to miss something. I've run into turbo matching that was way on the ragged edge of turbine inlet pressure design limit at peak power, causing signs of problems on teardown. If the turbine inlet pressure exceeds what the valve system was designed for, you might get valve float. Would you actually notice it in the real world, from winding out your hybrid turbo banging through gears a bit? Probably not.

The nice thing about single scroll turbos is that they tend to be better on pumping work and backpressure at high speed than twin scrolls, depending on how you compare the parameters. You've got the pulse tuning aspect you are fighting though (blowdown interference) with a single scroll. That's why you'll see sort of compromise designs, like the low-mount turbo on the LGT which has a divided manifold and a single scroll turbo.

The other option is to control the backpressure and pumping work with the exhaust valve events. If you look at the newest Audi turbo DI engines with Audi ValveLift on the exhaust cam, they are using basically divided manifolds all the way up to the inlet. The turbo is still a single scroll, but at low speed high load they switch to a short duration exhaust profile with long expansion ratio/no blowdown. This gives you the same effect as a twin scroll at low speeds, without having the extra pumping and backpressure of a twinscroll at high speed.
arghx7 is offline   Reply With Quote
Old 05-10-2014, 12:37 AM   #10
Ultimateone
Scooby Specialist
 
Member#: 48025
Join Date: Nov 2003
Chapter/Region: NESIC
Location: By the Ocean, MA
Vehicle:
2015 WRX
Ice Silver Mettalic

Default

Really cool post
Ultimateone is offline   Reply With Quote
Old 05-10-2014, 01:16 AM   #11
GrpB
Scooby Newbie
 
Member#: 101976
Join Date: Dec 2005
Default

Quote:
Originally Posted by arghx7 View Post
^^ When you start to look at it one dimensionally like that, (simple calculation using crank angle resolved values and geometric parameter) it's certainly possible to miss something.
My post was about engine dyno data. Not theory. If the valve is open, there is 0 valve lash, at maximum cylinder pressure there is a V in the curve of lash vs. crank angle due to valve head flexure, e.g. minimum valve lash occurs at max cylinder pressure, it is not static through the combustion event, nor is lash fixed with respect to coolant temp or exhaust temp measured at the port, it varies with load - it's solid data and I would know if the valves were not being controlled by the cam and if not, why. In any case, misfire is the real enemy which can happen even if the valves are in control.

I have had many iterations of camshaft profile varying cam timing and valve lift (based on engine simulation data) ground for the same engine in order to balance some of these competing parameters and was relating what my comparison of that data showed.
GrpB is offline   Reply With Quote
Old 05-10-2014, 07:30 AM   #12
arghx7
Scooby Specialist
 
Member#: 232940
Join Date: Dec 2009
Location: cold
Default

Quote:
Originally Posted by GrpB View Post
My post was about engine dyno data. Not theory. If the valve is open, there is 0 valve lash, at maximum cylinder pressure there is a V in the curve of lash vs. crank angle due to valve head flexure, e.g. minimum valve lash occurs at max cylinder pressure, it is not static through the combustion event, nor is lash fixed with respect to coolant temp or exhaust temp measured at the port, it varies with load - it's solid data and I would know if the valves were not being controlled by the cam and if not, why. In any case, misfire is the real enemy which can happen even if the valves are in control.
I'm not sure how that relates to an exhaust valve staying open longer than it should ("floating") due to excessive pressure in the turbo manifold. I'm talking about with the cam phasing at a representative position at high speeds, having full exhaust lift way after initial blowdown with most in-cylinder pressure relieved.



We can set that discussion aside though and agree that, overall, relieving pre turbo backpressure is better for a turbo engine when you're trying to make good peak power.
arghx7 is offline   Reply With Quote
Old 05-10-2014, 10:01 AM   #13
rexworx
Scooby Guru
 
Member#: 103232
Join Date: Dec 2005
Chapter/Region: Tri-State
Location: EWG3071KelfordCams276/272
Vehicle:
MY05 GDA,MY04FXT6spd
2.5ltr,PPG,Front LSD,4.44

Default

Very Cool Lance! Ive Been wanting to hook up a pre turbo exhaust pressure sensor to help with tuning AVCS etc...

Keep up the great testing!

Ian Hayes,
rexworx is offline   Reply With Quote
Old 05-10-2014, 12:13 PM   #14
SenorDucK
Scooby Specialist
 
Member#: 327511
Join Date: Jul 2012
Chapter/Region: MWSOC
Location: Chicagoland
Vehicle:
13' WRX 6 Speed
11sec VF52 EL-EWG-E85

Default

thanks for sharing this test and results! Makes me feel that much better about mine
SenorDucK is offline   Reply With Quote
Old 05-10-2014, 11:48 PM   #15
Lazzydog
Scooby Newbie
 
Member#: 240287
Join Date: Mar 2010
Chapter/Region: SCIC
Location: Ridgecrest
Vehicle:
2012 WRX
SWP

Default

Lots of complicated engine dynamics conversations going on here. For the simple folk in the room. Do different header setups (UEL/EL, larger/smaller primaries etc.) affect the EMAP/EGBP numbers especially when compared to stock manifolds?
Lazzydog is offline   Reply With Quote
Old 05-11-2014, 07:46 PM   #16
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

Awesome thread !
Bad Noodle is offline   Reply With Quote
Old 05-12-2014, 12:25 AM   #17
GrpB
Scooby Newbie
 
Member#: 101976
Join Date: Dec 2005
Default

Quote:
Originally Posted by arghx7 View Post
I'm not sure how that relates to an exhaust valve staying open longer than it should ("floating") due to excessive pressure in the turbo manifold.

We can set that discussion aside though and agree that, overall, relieving pre turbo backpressure is better for a turbo engine when you're trying to make good peak power.
It relates to actual valve events because real time measurment of the distance from the tappet to the cam base circle is a very robust way to measure the actual valve events in a fired engine without very fast degradation of the measurement system. When an exh valve opens unintentionally you can see it in the data. And from what I have seen, even if the presssure in the exh port is much higher than the pressure in the cylinder such that P1xA1 > P2xA2, including the complex/dynamic mechanical parameters at either end, either at the end of that cylinder's blowdown, or at the start of another cylinder's blowdown where communicated pressure in the manifold is very high and direct, I have not seen evidence of valve float due to this pressure. Misfire, yes, but not during normal combustion. Unless you orifice the exh cold end to artificially make the pressure sky high, but even then you get misfire first, exh valve float isn't the real issue.

And yes, I agree, higher pressure ratio is good on the hot end just as it is good on the cold end.
GrpB is offline   Reply With Quote
Old 05-12-2014, 09:50 AM   #18
VladiWrX
Scooby Specialist
 
Member#: 145658
Join Date: Apr 2007
Location: NorCal
Vehicle:
On my 5th scoob
and lovin it

Default

Quote:
Originally Posted by Lazzydog View Post
Lots of complicated engine dynamics conversations going on here. For the simple folk in the room. Do different header setups (UEL/EL, larger/smaller primaries etc.) affect the EMAP/EGBP numbers especially when compared to stock manifolds?
My humble take on it would be yes, since pressure is a measurement of the restriction of flow, although the turbine/hotside is the ultimate bottleneck in this case, and as demonstrated by OP there is measurable benefit to relieving this pressure pre-bottle neck.

Thanks to Cobb for posting these results, very interesting.
VladiWrX is offline   Reply With Quote
Old 05-12-2014, 10:23 AM   #19
wgr73
Scooby Specialist
 
Member#: 232458
Join Date: Dec 2009
Chapter/Region: SWIC
Location: Las Cruces, El Paso
Vehicle:
2008 STi (OBP)
CAMTuning.com

Default

Quote:
Originally Posted by Cobb Tuning View Post
Event: R&D Dyno Testing
Location: COBB Tuning Surgeline
Ambient Temp: Mild - 60's
Elevation: Sea Level
Weather: Mild

Car: 2010 WRX - COBB Tuning R&D Vehicle - "Ketchup"
Tuner: Lance Lucas
Dyno Info: Mustang AWD-500-SE
Transmission: OEM 2009 5MT
Gear: 3rd

Target Boost: Wastegate Pressure (0% WGDC)
Engine/Power Modifications: Stage2+SF (COBB Turboback Exhaust, COBB SF Intake/Airbox System). COBB 44mm EWG Kit w/atmospheric dump installed for EWG tests.
Tuning: COBB AccessPORT with v331 OTS maps (Stage2+SF 91 Octane with WGDC set to 0%)


Hey guys,

After finishing up a pretty big round of pending OTS updates for the 2009-2014 WRX, we decided to put our R&D WRX through some more rigorous testing regarding common modifications. Much like most customer cars, when equipped with full Stage2+Intake hardware, our car suffers from very severe boost creep. Even when it's not bad enough to cause a P0244 CEL, the fuel injectors are run right to the ragged edge from 5500 RPM to redline. Anyways...meet Ketchup the 2010 WRX. Look closely at the front passenger side of the bumper and you'll see the pressure measurement hose extending out and towards the dyno cart:




One of the more interesting but rarely-covered topics in turbocharged tuning is that of exhaust gas back pressure (EGBP), or EMAP (exhaust manifold absolute pressure). On a Subaru, this is generally measured somewhere between the exhaust manifold collector and the turbocharger itself.

Positive pressure in the exhaust manifold (a positive pressure differential between turbine inlet and outlet) is required to drive the turbocharger but also represents a trade-off against an engine's efficiency level and ability to displace air. The less pressure the engine has working against it when the exhaust valves are open, the happier the engine tends to be. In a perfect world, we would be able to create boost w/o restricting the engine at all. Physics don't allow this unfortunately so we work to balance them. In racing scenarios, aiming for an EGBP/Boost pressure ratio of 2.0 or lower is a very general rule of thumb. Just some general statements here and the topic is well-covered in a variety of tuning and automotive/SAE texts.

The goal of these tests were to test our kit for its relative ability to eliminate boost creep on Stage2 & Stage2+Intake on the 2009-2014 WRX. More importantly, in our previous testing, we found that EMAP was *very* high on the 2009-2014 WRX at high RPM, which is a contributor to their strong tendency for detonation when fuel quality is not great. Knowing this, we wanted to compare EMAP on both the stock IWG and the EWG configuration. We then calculated the relative pressure ratio between exhaust and intake manifold with each configuration.

All of these runs were completed with the boost control system disabled (wastegate duty cycle set to cap of 0%) to demonstrate the boost system's performance on the IWG and then the EWG. The EWG spring pressure chosen for this test was .9 bar.

This data was collected using a stock manifold that has been tapped at the collector for the AEM Exhaust Back Pressure kit with sensor logging via the Mustang Dyno PowerDyne controller/software.

Stage2+SF hardware vs. Stage2+SF+EWG hardware, both at wastegate boost levels:





** Clarification: "EMAP" is show as PSI relative to ambient atmosphere in this scenario, where the goal is comparing intake manifold boost (IMAP - Baro) against exhaust manifold pressure (EMAP - Baro).

Summation:

- On the IWG, EGBP/Boost ratios exceed 2.0 at high RPM. In other words, to produce ~12.5psi of boost at redline, pressure in the exhaust manifold is ~26psi with the stock internal wastegate.

- On the EWG, EGBP/Boost ratios are 1.5-1.6 at high RPM. In other words, to produce ~12.5psi of boost at redline, pressure in the exhaust manifold is ~19.5psi with the COBB 44mm EWG kit with atmospheric dump.

- EWG with atmospheric dump: muy bueno for power and efficiency purposes!


In the future we hope to extend this testing out to include recirculated EWG kits, upgraded turbos, different turbines and/or A/R housings with the same compressors, etc. Thanks for reading along!

Cheers

Lance

Absolutely awesome material Lance, thank you very much!


Quote:
Originally Posted by Clark Turner View Post
I have been testing exhaust backpressure for many years.... EWG makes more power which is what I have been saying for years while others say its not possible.

A lot of people say a lot of things. Not many people take the time to prove their theory and share it with others. Lance took it a step further and proved it, with data! Maybe that's why people were reluctant. Just a thought
wgr73 is offline   Reply With Quote
Old 05-12-2014, 11:41 AM   #20
Tripintaz
Scooby Specialist
 
Member#: 245218
Join Date: Apr 2010
Chapter/Region: South East
Location: FL
Vehicle:
2013 STI Limited

Default

Now if only you could make a non atmospheric dump EWG setup. Some of us hate the sound they make.
Tripintaz is offline   Reply With Quote
Old 05-12-2014, 11:49 AM   #21
Clark Turner
NASIOC Vendor
 
Member#: 178047
Join Date: Apr 2008
Chapter/Region: SWIC
Location: AZ/Vegas
Vehicle:
02 WRX STI Spec C
Black

Default

Quote:
Originally Posted by wgr73 View Post
Absolutely awesome material Lance, thank you very much!

A lot of people say a lot of things. Not many people take the time to prove their theory and share it with others. Lance took it a step further and proved it, with data! Maybe that's why people were reluctant. Just a thought

The argument online, was that if the car makes the same boost pressure its impossible for an external gate to flow more and have lower pressure because the internal and external gate would be at the same exact opening point.

It was a good laugh..

C
Clark Turner is offline   Reply With Quote
Old 05-12-2014, 06:34 PM   #22
DisoDisp
Scooby Newbie
 
Member#: 187648
Join Date: Aug 2008
Chapter/Region: International
Location: Finland
Vehicle:
2007 WRX

Default

Quote:
Originally Posted by Tripintaz View Post
Now if only you could make a non atmospheric dump EWG setup. Some of us hate the sound they make.
Plumb back EWG setups have been around for eons, but they pretty much defeat the point, plumb back = higher EGBP.
DisoDisp is offline   Reply With Quote
Old 05-14-2014, 01:40 AM   #23
Harey
Scooby Newbie
 
Member#: 270569
Join Date: Jan 2011
Default

Quote:
Originally Posted by DisoDisp View Post
Plumb back EWG setups have been around for eons, but they pretty much defeat the point, plumb back = higher EGBP.
I thought the main benefit of EWG is that at full boost it allows some of the exhaust flow to bypass the turbo wheel, thus lowering the EGBP (or EMAP). If you are loosing noticeable power when you change your EWG from atmosphere to plumb back then your flow path has not been designed well or your turbo back exhaust is too small.
Harey is online now   Reply With Quote
Old 05-14-2014, 11:58 AM   #24
Clark Turner
NASIOC Vendor
 
Member#: 178047
Join Date: Apr 2008
Chapter/Region: SWIC
Location: AZ/Vegas
Vehicle:
02 WRX STI Spec C
Black

Default

The workload of the exhaust system is increased when the External gate is plumbed back. If you have a restrictive exhaust, the benefit is lower.

C
Clark Turner is offline   Reply With Quote
Old 05-14-2014, 08:23 PM   #25
slowgenius
Scooby Specialist
 
Member#: 48350
Join Date: Nov 2003
Chapter/Region: MAIC
Location: Pittsburgh
Vehicle:
04 WRX

Default

Quote:
Originally Posted by Clark Turner View Post
The workload of the exhaust system is increased when the External gate is plumbed back. If you have a restrictive exhaust, the benefit is lower.

C
What if the dump tube is introduced down farther from the turbo, and the piping is enlarged further to say 3.5 inches in diameter? Does that make a difference?
slowgenius 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


All times are GMT -4. The time now is 01:26 AM.


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.