Welcome to the North American Subaru Impreza Owners Club Wednesday August 5, 2015
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 2.5L Turbo Powertrain (EJ Series Factory 2.5L 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 09-22-2005, 12:21 AM   #1
srf
Scooby Specialist
 
Member#: 50646
Join Date: Dec 2003
Chapter/Region: NWIC
Location: Bothell, WA
Vehicle:
2004 WRX STi
Java Black

Default The theory around boost target

I'm curious as to how the "target boost PSI" number is chosen, even after reading a couple dozen threads (and not having much luck with Google).

From what I've gleaned my theory so far is that you try to hit the target boost pressure relatively low in the RPM range, then boost tapers off as you approach redline, since more revolutions requires more air to be delivered in a given time period.

So then if your target boost pressure is too high, the turbo won't be able to provide enough CFM as the RPMs rise, and you'll end up with less power across the RPM range?

All this being the case, target boost pressure for a given turbo & engine combo is more or less a case of trial & error with dyno & road tunes? Then the target boost pressure would imply the rate at which boost tapers off.

Also I assume that how much a turbo heats up the air is part of the efficiency of a turbo. How would one turbo running hotter than another manifest itself in a UTEC log?
* Registered users of the site do not see these ads.
srf is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 09-24-2005, 01:42 AM   #2
TypeC
Scooby Guru
 
Member#: 9794
Join Date: Aug 2001
Chapter/Region: TXIC
Location: Texas
Vehicle:
02 2.5LWRX-Retired
335i w/twins

Default

Quote:
Originally Posted by srf
I'm curious as to how the "target boost PSI" number is chosen, even after reading a couple dozen threads (and not having much luck with Google).
Looking at the compressor map and plotting your flow/PR over rpm. That and going by the results/findings of others.

Quote:
Originally Posted by srf
So then if your target boost pressure is too high, the turbo won't be able to provide enough CFM as the RPMs rise, and you'll end up with less power across the RPM range?

All this being the case, target boost pressure for a given turbo & engine combo is more or less a case of trial & error with dyno & road tunes? Then the target boost pressure would imply the rate at which boost tapers off
The boost only tapers when the turbo is too small to push the air you want. If you had the choice, you wouldn't want it to taper.

Quote:
Originally Posted by srf
Also I assume that how much a turbo heats up the air is part of the efficiency of a turbo. How would one turbo running hotter than another manifest itself in a UTEC log?
Looking at Knock correction, EGT, timing, and know the point where your turbo is maxed out.

The best bet is to research the setup you want and set it in the range that seems to work for that combo. No need in reinventing the wheel. Let other people blow motors for you. Trust me
TypeC 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
The Tuning Boost Targets Thread Broxma Commercial ECU Reflashes 29 05-19-2014 09:53 AM
Anyway around the 24.75 psi target boost limit in the 16bit ECU? Phatron Open Source Reflashes 10 11-06-2008 06:24 PM
cobb stg 2 boost target Q/cobb rant lordzappo Engine Management & Tuning 6 10-03-2005 05:27 AM
boost targets????? Pavoni8297 Engine Management & Tuning 0 09-17-2005 11:10 AM
Cobb stage 2... not hitting boost target level... WRXVII Engine Management & Tuning 37 06-06-2004 12:14 AM


All times are GMT -4. The time now is 02:32 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2015 Axivo Inc.
Copyright ©1999 - 2015, North American Subaru Impreza Owners Club, Inc.