# Calculating proper forced induction **URL:** \ **Category:** SON240sx Automotive\ **Created:** [June 28, 2005, 8:28pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810 "2005-06-28T20:28:39Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![alesserfate](https://avatars.discourse-cdn.com/v4/letter/a/f6c823/32.png) [@alesserfate](https://forums.speedlife.net/u/alesserfate)\ **Post date:** [June 28, 2005, 8:28pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/1 "2005-06-28T20:28:39Z")
hey guys im making a home made centrifugal supercharger with possibly a heat exchanger to cool the air. I am concerned with the specifications I should focus on, I’ve been researching and so far I’ve been hitting the two same things, the CFM and the PSI. I have two questions: (1): ~appx how much CFM is required for a ka @ specific boost?; (2) when measuring the psi, it should be measured WHILE the oxygen is being consumed by the engine, correct ? Thanks in advance. ---
**Author:** ![TM1](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/tm1/32/5517_2.png) [@TM1](https://forums.speedlife.net/u/TM1)\ **Post date:** [June 29, 2005, 4:37am UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/2 "2005-06-29T04:37:30Z")
You need to be far more detailed… ---
**Author:** ![SHIFT\_KA24DET](https://avatars.discourse-cdn.com/v4/letter/s/b9bd4f/32.png) [@SHIFT\_KA24DET](https://forums.speedlife.net/u/SHIFT_KA24DET)\ **Post date:** [June 29, 2005, 11:41am UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/3 "2005-06-29T11:41:55Z")
> [@TM](#): > > You need to be far more detailed… (1): ~appx how much CFM is required for a ka @ specific boost? - What the hell does that mean? (2) when measuring the psi, it should be measured WHILE the oxygen is being consumed by the engine, correct ? - You lost me… ---
**Author:** ![SHIFT\_KA24DET](https://avatars.discourse-cdn.com/v4/letter/s/b9bd4f/32.png) [@SHIFT\_KA24DET](https://forums.speedlife.net/u/SHIFT_KA24DET)\ **Post date:** [June 29, 2005, 11:43am UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/4 "2005-06-29T11:43:04Z")
I go by the rule of thumb measure once cut twice. Too much theroy kills the whole fun of building and tuning cars IMO. ---
**Author:** ![Sven](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@Sven](https://forums.speedlife.net/u/Sven)\ **Post date:** [June 29, 2005, 4:19pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/5 "2005-06-29T16:19:58Z")
I hope you have an engineering background if you are planning on building one completly yourself. And you don’t sound like you do if you are asking questions like #2 ---
**Author:** ![alesserfate](https://avatars.discourse-cdn.com/v4/letter/a/f6c823/32.png) [@alesserfate](https://forums.speedlife.net/u/alesserfate)\ **Post date:** [June 29, 2005, 9:10pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/6 "2005-06-29T21:10:15Z")
everyone begins to learn somewhere, thanks alot guys ---
**Author:** ![Sven](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@Sven](https://forums.speedlife.net/u/Sven)\ **Post date:** [June 29, 2005, 9:59pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/7 "2005-06-29T21:59:45Z")
Well then I’ll get you started. When people talk about PSI of boost it is just the measured pressure in the intake manifold. Unboosted cars should see a vacuum because the engine is sucking up air. (aka negative PSI) ---
**Author:** ![alesserfate](https://avatars.discourse-cdn.com/v4/letter/a/f6c823/32.png) [@alesserfate](https://forums.speedlife.net/u/alesserfate)\ **Post date:** [June 29, 2005, 10:15pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/8 "2005-06-29T22:15:00Z")
pressure measured in the intake manifold, at maximum boost (when engine is revving - and thereby comsuming oxygen at the same time as the turbine is producing) ? ---
**Author:** ![Sven](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@Sven](https://forums.speedlife.net/u/Sven)\ **Post date:** [June 29, 2005, 10:25pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/9 "2005-06-29T22:25:33Z")
What are you talking about man? You are asking me if you measure pressure at maximum boost? pressure is boost. So if you measure boost at maximum boost that will tell you what your maximum boost is yes … :roll: How else could you measure it? The engine is always sucking in air … engines are basically giant air pumps. ---
**Author:** ![alesserfate](https://avatars.discourse-cdn.com/v4/letter/a/f6c823/32.png) [@alesserfate](https://forums.speedlife.net/u/alesserfate)\ **Post date:** [June 29, 2005, 10:27pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/10 "2005-06-29T22:27:47Z")
i tried to measure the turbine pressure by covering the hole and sticking a boost gauge on it, before it was even hooked up to my intake and just spinning in free air, yeah i know it sounds dumb, but now i know… lol ---
**Author:** ![Sven](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@Sven](https://forums.speedlife.net/u/Sven)\ **Post date:** [June 29, 2005, 10:32pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/11 "2005-06-29T22:32:13Z")
oh man … I can’t wait to see the finished product. You do realize you need a way to DRIVE the turbine right? Like a supercharger is belt driven not just a big fan in the intake … And a turbo has a turbine driven by exhaust gas … ---
**Author:** ![alesserfate](https://avatars.discourse-cdn.com/v4/letter/a/f6c823/32.png) [@alesserfate](https://forums.speedlife.net/u/alesserfate)\ **Post date:** [June 29, 2005, 10:32pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/12 "2005-06-29T22:32:59Z")
> [@Sven](#): > > You do realize you need a way to DRIVE the turbine right? Like a supercharger is belt driven not just a big fan in the intake … And a turbo has a turbine driven by exhaust gas … im not dumb, thats common sesne ---
**Author:** ![Sven](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@Sven](https://forums.speedlife.net/u/Sven)\ **Post date:** [June 29, 2005, 10:35pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/13 "2005-06-29T22:35:49Z")
Well you’re certainly going to give Janto’s theory a run for its money Should be fun ---
**Author:** ![Pavel](https://avatars.discourse-cdn.com/v4/letter/p/a4c791/32.png) [@Pavel](https://forums.speedlife.net/u/Pavel)\ **Post date:** [June 29, 2005, 10:49pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/14 "2005-06-29T22:49:33Z")
> [@Sven](#): > > Unboosted cars should see a vacuum because the engine is sucking up air. (aka negative PSI) unboosted = N/A… just say NA. boosted cars also see vacuum when they are not in boost. Interesting idea though, hopefully it works out. On a side note, does the NA motor vacuum get to 0 when you rev it? It only makes sense that the vacuum numbers fall since the FPR opens at lower vacuum. ---
**Author:** ![SHIFT\_KA24DET](https://avatars.discourse-cdn.com/v4/letter/s/b9bd4f/32.png) [@SHIFT\_KA24DET](https://forums.speedlife.net/u/SHIFT_KA24DET)\ **Post date:** [June 29, 2005, 10:53pm UTC](https://forums.speedlife.net/t/calculating-proper-forced-induction/86810/15 "2005-06-29T22:53:41Z")
> [@Sven](#): > > Well you’re certainly going to give Janto’s theory a run for its money > > Should be fun Ahh ha ha ha :thefinger: