Tuning Alliance Posted December 17, 2015 Share Posted December 17, 2015 (edited) I've been talking to a lot of people with upgraded oem style turbos VF40, VF46, VF52, and so on. I wanted to post my thoughts on what is an effective upgrade and what is not from a turbo geometry perspective. For example, I dont advise installing a larger compressor wheel on a VF40 as that configuration is already largerly turbine restricted. Installing a bigger comp wheel further unbalances the flow rates, increases back pressure at full boost, and may hurt power levels overall. (***under construction***) http://i463.photobucket.com/albums/qq357/tuningalliance/comparo.png I'd like to talk about wheel sizing between compressor and turbines. As you can see I highlighted the "Inlet/out" ratio, which is simply the inlet diameter (compressor inducer) divided by the outlet diameter (turbine exducer). A perfect turbo would have a 1.00 ratio, and as you can see a GTX3582R is pretty darn close. A value over 1.00 indicates the turbine section is the restriction point, where as a value under 1.00 indicates a compressor restriction point. A stock VF40 has a 1.08 ratio. Meaning is largely turbine restrictive, and upgrading the compressor will only worsen this ratio, and will not allow for additional power as the small outlet is the overall restriction point. This turbo would likely benefit from turbine wheel clipping or turbine housing porting. As upgrading the turbine section doesn't really make financial sense. A stock VF52 has a 0.96 ratio, meaning it could benefit from a little bit bigger compressor inlet size. So a little larger billet wheel could be a helpful upgrade. Edited December 17, 2015 by Tuning Alliance Contact us for all your tuning and performance parts needs! Etuning the legacy community since 2008! Follow us on FACEBOOK | INSTAGRAM [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
Tuning Alliance Posted December 17, 2015 Author Share Posted December 17, 2015 (edited) Next I want discuss the reality of putting a larger compressor or turbine wheel inside a stock housing. When you machine the stock turbine housing to accept a larger wheel, there are some disadvantages to be noted. A stock turbine housing has internal passages which are carefully sized in volume, width, and the delivery channel which directs flow on to the blades is a matching dimension. This gives the most effective delivery of exhaust into the wheel. If you install a larger wheel there is now a mismatch of these dimensions and a portion of the trailing edge of the blades that is not in fact hit directly with exhaust as it would in a turbine housing design for that turbine. Many people only think about the increase in diameter when they are picturing the larger wheel inside the housing. I'm not saying it doesn't work, as it does work. What I'm saying that all of the bolt-on upgraded turbos, do not have the proper volume or channel to drive the turbine at its maximum efficiency. The same thing goes for the compressor housing. Other aftermarket non bolt-on turbos spool faster and are more efficient due to this fact. This is why I often urge people to use either a OEM turbo or a full rotated setup with a fully matched configuration. http://i463.photobucket.com/albums/qq357/tuningalliance/turbine_1.jpg http://i463.photobucket.com/albums/qq357/tuningalliance/detail%20turbine_1.jpg Edited December 17, 2015 by Tuning Alliance Contact us for all your tuning and performance parts needs! Etuning the legacy community since 2008! Follow us on FACEBOOK | INSTAGRAM [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
Tuning Alliance Posted December 17, 2015 Author Share Posted December 17, 2015 Reserved (***under construction***) Contact us for all your tuning and performance parts needs! Etuning the legacy community since 2008! Follow us on FACEBOOK | INSTAGRAM [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
Tuning Alliance Posted December 17, 2015 Author Share Posted December 17, 2015 Reserved Contact us for all your tuning and performance parts needs! Etuning the legacy community since 2008! Follow us on FACEBOOK | INSTAGRAM [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
08Legacy-GT Posted December 17, 2015 Share Posted December 17, 2015 lol right from our discussion 2017 Subaru STI 2008 Subaru Legacy 2.5i limited Link to comment Share on other sites More sharing options...
Tuning Alliance Posted December 17, 2015 Author Share Posted December 17, 2015 lol right from our discussion People keep asking and I find myself explaining this stuff twice a day. Time to get it out there then I can just link people to it. More to come!!! Contact us for all your tuning and performance parts needs! Etuning the legacy community since 2008! Follow us on FACEBOOK | INSTAGRAM [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
magnusonsubie Posted December 19, 2015 Share Posted December 19, 2015 Sub'd to read later 2005 Vader Wagon Material Tests on Ringland Failure Piston I should have held off and purchased a wagon instead of the spec.B Link to comment Share on other sites More sharing options...
StkmltS Posted December 19, 2015 Share Posted December 19, 2015 Sub'd Sent from inner space. My DiySB rebuild Got Misfires? Link to comment Share on other sites More sharing options...
compsurge Posted December 19, 2015 Share Posted December 19, 2015 In for CFD analysis. Link to comment Share on other sites More sharing options...
Jaybird2013 Posted December 22, 2015 Share Posted December 22, 2015 I can see now why you advised me against upgrading the wastegate actuator. Link to comment Share on other sites More sharing options...
TheMonaLisa Posted December 22, 2015 Share Posted December 22, 2015 Very interesting Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
rebourne Posted April 11, 2016 Share Posted April 11, 2016 (edited) sub'd. images are broken... nvm. Edited April 11, 2016 by rebourne pic thread build thread Link to comment Share on other sites More sharing options...
Tuning Alliance Posted April 11, 2016 Author Share Posted April 11, 2016 sub'd. images are broken... Are you looking on a phone or computer? I'm seeing them in google chrome browser on my PC. -Brian Contact us for all your tuning and performance parts needs! Etuning the legacy community since 2008! Follow us on FACEBOOK | INSTAGRAM [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
Rhitter Posted April 11, 2016 Share Posted April 11, 2016 I see the images on my phone. Must be on Rebourne's side. My OBXT build Link to comment Share on other sites More sharing options...
magnusonsubie Posted April 11, 2016 Share Posted April 11, 2016 I can see them on my phone via Tapatalk and on my computer via chrome. Must be on Rebourne's side 2005 Vader Wagon Material Tests on Ringland Failure Piston I should have held off and purchased a wagon instead of the spec.B Link to comment Share on other sites More sharing options...
rebourne Posted April 11, 2016 Share Posted April 11, 2016 Fine now on PC and phone... Guess it was a blip on my side. "Screen capture or it didn't happen!" as the saying goes. pic thread build thread Link to comment Share on other sites More sharing options...
Tuning Alliance Posted April 11, 2016 Author Share Posted April 11, 2016 Okay cool. Contact us for all your tuning and performance parts needs! Etuning the legacy community since 2008! Follow us on FACEBOOK | INSTAGRAM [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
mzsinko84 Posted March 4, 2021 Share Posted March 4, 2021 Does the 2005 Legacy GT turbocharger have a 12 blade billet from the factory? I ordered a 12 blade billet thinking installing it would make a difference or make an improvement. Link to comment Share on other sites More sharing options...
Max Capacity Posted March 30, 2021 Share Posted March 30, 2021 Does the 2005 Legacy GT turbocharger have a 12 blade billet from the factory? I ordered a 12 blade billet thinking installing it would make a difference or make an improvement. 9 blade on the hot side. Here's my old vf40 https://legacygt.com/forums/showthread.php/142-000-miles-oem-turbo-168561.html 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
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