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equation for displacement vs psi

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Old 04-16-2003, 04:29 PM
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equation for displacement vs psi

Ok effective when you use blowers your in a sense faking increased displacement, yeah i know thats massive oversimplification but bear with me. So anyway i was wondering if theres a way that you can calculate what the displacement effectively is based on actual displacement vs psi. Anyone have something?
 
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Old 04-16-2003, 04:53 PM
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Old 04-16-2003, 05:27 PM
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What would be the reason behind wanting to know that? So that you could compare our motor to a larger N/A application?

I suppose there would be a way to figure it out, technically we may be displacing as much air as a larger motor, since the blower pressurizes it.

Or maybe I have been sniffing too many exhaust gasses recently and I'm just rambling.
 
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Old 04-16-2003, 05:41 PM
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yeah sorta, im just kinda curious exactly what sorta displacement a 5.4 L at 20 psi would actually require.

There has to be a way to calculate it i just dont know what it is. I think regular air is like 8.8 psi, at sea level. i dont know how the additional psi compares etc. im suprised no one has chimed in on this one yet, i would think tuners would know.
 
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Old 04-16-2003, 05:47 PM
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An "old" mechanic told me that each pound of boost
increased compression by .3 ... I dunno about Displacement.
 
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Old 04-16-2003, 05:51 PM
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Originally posted by grinomyte
yeah sorta, im just kinda curious exactly what sorta displacement a 5.4 L at 20 psi would actually require.

There has to be a way to calculate it i just dont know what it is. I think regular air is like 8.8 psi, at sea level. i dont know how the additional psi compares etc. im suprised no one has chimed in on this one yet, i would think tuners would know.
I was told at 8lbs of boost, we have doubled the displacement. Don't know if thats true or not.

btw.......sea level is 14.7 psi
 
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Old 04-16-2003, 06:11 PM
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I was always told you add the two together
Another words the Engine is 330 CID
And the Eaton 115 is it ?
Making it 445 CID

make sense

QUOTED BY EATON

In 1949, Eaton toyed with a helical rotor supercharger and even built a 75-cubic inch displacement prototype.
 
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Old 04-16-2003, 06:19 PM
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Originally posted by Rob_02Lightning
I was always told you add the two together
Another words the Engine is 330 CID
And the Eaton 115 is it ?
Making it 445 CID

make sense

QUOTED BY EATON

In 1949, Eaton toyed with a helical rotor supercharger and even built a 75-cubic inch displacement prototype.
It's an m112. So 330 + 112 = 442.
 
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Old 04-16-2003, 06:55 PM
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So we are looking at a 440 at 8psi? How many of you would rather start with a 440 and work it from there? I dont know enough about older cars to know what kind of potential is there, or how much would have to be invested to achieve what many of you already have. But its an interesting thought...

Keith
 
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Old 04-16-2003, 07:48 PM
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No no no...

OK, here's the formula:

330 * ( (PSI boost+14.7)/14.7)

That will give you the best guess for a NA engine. Note that it isn't the same because the SC will use power, but it's as close as spitting distance will get you...

So:

Stock: 509 ci
4lb pulley: 599 ci
6lb pulley: 644 ci
10lb pulley: 734 ci

This is just a blind formula to compare air usage. It does not imply anything about power or torque curves.

Coldie
 
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Old 04-16-2003, 07:49 PM
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Adding the cubic inch displacement of the s/c'r to the eng's displacement is correct. See this article and read the info under the last pic:

http://www.carcraft.com/techarticles/93500/index2.html

I searched all over and could not find an equation. It's just simple addition.

Dan
 
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Old 04-16-2003, 07:52 PM
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there we go, thanks coldie yeah thats what i was after, 8.8 i think i pulled from gravites feet per second? i dont know that number means something. Thanks everyone.
 
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Old 04-16-2003, 07:54 PM
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oh and i seriuosly doubt the name of the s/c implies cubic displacement or anything pertaining to it, boost is determined by how fast the s/c so i dont think you can determine it until you know what pullies and what engine its gonna run on.
 
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Old 04-16-2003, 07:56 PM
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Originally posted by grinomyte
there we go, thanks coldie yeah thats what i was after, 8.8 i think i pulled from gravites feet per second? i dont know that number means something. Thanks everyone.
FYI......acceleration towards earth is 9.81m/s^2 (freefall)........LOL

You got your numbers all messed up

I hate being an engineer......you remember all these stupid numbers and formulas.........

--Joe
 
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Old 04-16-2003, 08:00 PM
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alright soap, cmon fork it over itll drive me nuts, whats 8.8? SOMETHING is 8.8
 


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