# Calculating Turbo Size for Twin Turbo Setup

**URL:** <https://forums.speedlife.net/t/calculating-turbo-size-for-twin-turbo-setup/126443>\
**Category:** SON240sx Automotive\
**Created:** [July 21, 2009, 5:23pm UTC](https://forums.speedlife.net/t/calculating-turbo-size-for-twin-turbo-setup/126443 "2009-07-21T17:23:09Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![NoSkillz](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/noskillz/32/5606_2.png) [@NoSkillz](https://forums.speedlife.net/u/NoSkillz)\
**Post date:** [July 21, 2009, 5:23pm UTC](https://forums.speedlife.net/t/calculating-turbo-size-for-twin-turbo-setup/126443/1 "2009-07-21T17:23:09Z")

</div>

In short  
i need to flow 40lb/min of air to meet my horsepower goals and I’ve calculated a pressure ratio of 1.74 desired. (5.7psig manifold pressure)

now I have two t25’s available to me. Is it possible to use these without exceeding the Choke line.

Looking at the turbo map 1.74 will give me 20lbs (im assuming that a second turbo would just double the value) but this doesn’t seem safe.

In short do i have to increase boost to move my self in a safer range, and to what point.

now this is the turbo map im following

[![](http://www.not2fast.com/turbo/maps/t2560trim2kw.gif) ](http://www.not2fast.com/turbo/maps/t2560trim2kw.gif)

I’ve just learned all this stuff today, so i may be missing some important concepts here. If you want all the values that i used for my calculations just let me know… to lazy to type them out.

Steve