Welcome to the North American Subaru Impreza Owners Club Tuesday September 16, 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 Archives > NASIOC Archives > STi Forum Archive

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.
 
 
Thread Tools Display Modes
Old 07-21-2003, 01:28 PM   #1
RS_4U2NV
Scooby Newbie
 
Member#: 24269
Join Date: Sep 2002
Location: ATL GA
Vehicle:
2006 LGT
GRP

Question TMIC airflow improvement

I have heard of people using splitters in the hood scoop to make the air entering turn the corner and better distribute airflow over the intercooler. Has anybody heard of using vortex generators to help the air make the downward turn into the intercooler?

I have seen vortex generators used on NASCAR cars in front of NACA ducts to promote better airflow. Of course this is also the reason why NACA ducts have sharp corners at the surface.

Turbulent air is less likely to separate from the surface and therefore would make the turn down into any air inlet easier. So, has anyone tried using vortex generators for their hood scoop?
* Registered users of the site do not see these ads.
RS_4U2NV is offline  
Old 07-21-2003, 02:25 PM   #2
happasaiyan
Scooby Specialist
 
Member#: 37731
Join Date: Jun 2003
Chapter/Region: MWSOC
Location: Rolling Meadows, IL
Default

just so you know, the STi scoop already has an air splitter.
happasaiyan is online now  
Old 07-21-2003, 04:41 PM   #3
hyperion
Scooby Newbie
 
Member#: 34699
Join Date: Mar 2003
Default

In my opinion, it's a mistake to talk about aerodynamic flow through geometry like an intercooler. The path is so tortured that really all you care about is pressure gradients. If you were to measure the pressure at the top and bottom of the I/C, this is the only thing that matters. The flow through this system is highly turbulent and separated as it is. The hood scoop is probably already operating in the turbulent boundry layer anyway--note how leaves sometimes stay on your windscreen? There are wierd recirculating flow patterns there in cars with upright windscreens like the STi.

Now, if the pressure at the top-front of the I/C is less than the top-rear, then you might have an argument to put some control vanes to try and redirect the flow. But remember, every time you put something else in the flow, you increase pressure losses. I would first look to see some very sound empirical data on this subject before throwing a buch of wings, fins, and flow disruptors in your scoop or on your hood. I have a hard time believing this phenomena actually exists or has any appreciable effect while driving the car on the street/track.

Also, measure the area of the I/C versus the scoop. The peak efficiency for intercoolers is between 15-30 MPH. I would expect the choke area of the scoop to be about two or three times smaller, meaning that the car works best (from a intake charge cooling perspective) at 45-90 MPH.

Remember, air doesn't act like a bunch of tiny racketballs. Kinetic theories of fluid have been wrong since Bernoulli.

-ch
hyperion is offline  
Old 07-21-2003, 06:40 PM   #4
Beldrueger
Scooby Newbie
 
Member#: 31822
Join Date: Jan 2003
Location: Dallas - Boston
Default

Are you suggesting that a smaller hood scoop would actually work better at higher speeds because the inverted funnel effect would slow the speed of the air to a more efficient rate? ... this is groundbreaking stuff ... if so ... please clarify
Beldrueger is offline  
Old 07-22-2003, 06:24 AM   #5
RS_4U2NV
Scooby Newbie
 
Member#: 24269
Join Date: Sep 2002
Location: ATL GA
Vehicle:
2006 LGT
GRP

Default

It is true that if an air inlet is too big, it will become inefficient. Depending on the spacing and density of vanes in the intercooler, it will only allow a certain amount of air to flow past it and at a certain speed. If the air inlet(or hood scoop in this case) is trying to feed too much air, a portion of that will not be able to go through the intercooler. The extra air has nowhere to go but to recirculate and spill back out through the inlet or seep out through the seems in the ducting to the inlet. This will cause inefficiency and choked flow.

The big "however" is...the science/math behind this is unpredictable to say the least and will only get you in the ball park. Testing is required to fine tune the size of your inlet. There is no way for any of us to know how well subaru sized the hood scoop or for what range of speeds.

So, it is slightly conceivable that if you ONLY run at high speeds, a smaller hood scoop may be better. However, the more likely solution would be to get a more efficient, higher flowing intercooler to handle the larger flow of air.
RS_4U2NV is offline  
 

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
Will A TMIC Improve lag on a 20 G Turbo? plus plus plus Newbies & FAQs 12 05-18-2007 07:25 AM
Improve Airflow on MY02 Stock Scoop 02WHITEDUB Newbies & FAQs 3 10-16-2005 08:51 AM
home improvement thread 3: home improvement with a vengeance AC Lerok Off-Topic 4 05-23-2005 08:50 PM
SAFC Airflow/pressure signal WeapoN-R Normally Aspirated Powertrain 0 06-13-2001 12:11 AM
S-afc install PT II: The AirFlow Conflict Bahumut Normally Aspirated Powertrain 10 06-07-2001 10:43 AM


All times are GMT -4. The time now is 04:36 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.