I make some calculation to found why my boost pressure is so high and I found this:

Supercharger Compression ratio:

2.7'' pulley: 19 psi
atmospheric pressure: 14.7 psi

19 + 14.7 = 33.7 psi(absolute pressure)

33.7 / 14.7 = 2.29

2.29@1 is the compression ratio of the supercharger

now my atmospheric pressure of the supercharger, is the 14.5 psi of the turbo, because the supercharger is feed by the turbo

14.5 * 2.29 = 33.21 psi of boost

suppose my bypass valve of the supercharger leave 3-4psi of boost go down directly to the head

my boost is now 28-29 psi



4'' pulley: 7 psi
atmospheric pressure: 14.7

7 + 14.7 = 21.7 psi(absolute pressure)

21.7 / 14.7 = 1.48


1.48@1

14.5 * 1.48 = 21.46 psi ....approx

 

yeah... so?

like thats cool, but whats your point?

 

I dont know much about this! In fact im building mine and still trying to figure about where to put the supercharger bypass boost controller! lol

But if you open the bypass valve wouldnt the pressure on both sides of the blower be the same? IE 15 psi on both sides of the blower? And then anything from the supercharger after that be pointless?

It sounds like to me that your making the blower work to hard! I think you should run a stock pulley and lower the pressure supplied by the supercharger and let the turbo do all the work!

The turbo outflow the supercharger right? So you should want the supercharger to do nothing but spool the turbo up!

I think its crazy what your seeing for boost! Mine will be done by the end of the week and ill go take a spin and see what she does!

 

When the bypass valve opens, thats exactly what its doing, making the air BYPASS the supercharger. Thats how zoomer is doing it. The supercharger isnt doing ANYTHING after 12psi. At that point the bypass valve opens and the turbo is already spooled to say 23psi on its own. The engine is now being fed directly from the turbo. All the supercharger is doing is basically free spinning because its not getting any air.

 

I would like to see a vid of your's

 

i wish i was pushing 19psi with my 2.7

 

no no no no no no, the blower doesn't "work to hard". The turbo doesn't "outflow the supercharger" either. Did you not understand the formulas? The supercharger EFFECTIVELY compresses however much air is supplied to it. If there is no turbo, then the multiplier is 1, hence why the supercharger compresses air by itself with the formula 2.29@1 making 19psi with a 2.7 pulley.

You then add 14.5psi from a turbo, you are no longer feeding the supercharger 2.29@1, you are now feeding the supercharger 2.29@14.5, do you see now? It doesn't make the supercharger work harder or the turbo should outflow the supercharger. It MULTIPLIES THE AIR BECAUSE THE SUPERCHARGER "COMPRESSES".

So, just to break it down in lamens terms, a supercharger by itself has to suck 0 pressure and multiply that to make however much boost decided by the pulley and revolutions the supercharger makes to compress air. If you throw a turbo into the mix, the supercharger now compresses BOOST, not just air, and now makes even more pressure. Nothing works harder. The supercharger COMPRESSES. That's what it does. It will compress 0 pressure or 30psi of pressure. Either way, it will compress.

 

But, our type of supercharger does not 'compress' air. It simply moves it.

 

no, it compresses in the intake manifold.

 

When dealing with pressure ratio's, I think you should always calculate with absolute pressures. (Like you did in the beginning, but not when you multiplied the 14.5 psi boost pressure.)

Not really convinced if it really works like this with roots blowers, as they have no internal compression....

 

they still compress.

 

I have a 8 psi spring on mine with the stock pulley so the pressure ratio is:

3.35 inch pulley = 12.5 psi

atmophereic + pressure = (14.7+12.5) = 26.7

(PR= 26.7/14.7) = 1.81 PR

So in your theroy sound pretty good in that the supercharger will try and move 8 psi at a rate of 1.81 to 1 ratio? right

So my setup should make in theroy 14.5 psi total? Does that sound right?

It makes sense I guess!

 

Lots of misconjecture flying around in here.

 

indeed

 

well, if we're wrong, then please by all means correct us. Cause being wrong and still thinking I'm right isn't cool. I'd like to be right than be wrong.

 

time to break out the old physics book

 

1. your numbers are off. 1 bar is NOT 14.7 it is 14.50

redo your numbers and get back to us.

 

Makes sense if my calculation is correct

I search on the net, to find something from the subject

the amospheric pressure is equal to:

- 101325 Pa
- 1013 hPa
- 1.01325 bar
- 1 atmosphere
- 760 mm Hg
- 14.69594 Psi

 

So Is This How Much U Got??

 

[QUOTE=Bill@usd;2862297]Makes sense if my calculation is correct

I search on the net, to find something from the subject


We will find out if ups would drop of my wastegate! dam brown! lol

So if I go out tonight and hit 15 psi then we will know that the math is right!

Bill i think you need to post the video you posted in the other thread showing your guage hitting 28-29 psi with only a 14.5 psi gate!

 

this is the video

half throttle....for now

http://videos.streetfire.net/video/c...rge_182407.htm

 

::sigh::

14.5038 psi
1000 mbar
100000 N/m²
100000 Pa
1000 hPa
100 kPa
0.1 MPa
1.01972 kgf/cm²
10197.2 mmH2O 4°C (39.2°F)
1019.72 cmH2O 4°C (39.2°F)
10.1972 mH2O 4°C (39.2°F)
401.463 inH2O 4°C (39.2°F)
33.4553 ftH2O 4°C (39.2°F)
750.062 mmHg 0°C (32°F)
75.0062 cmHg 0°C (32°F)
29.5300 inHg 0°C (32°F)
750.062 Torr
750062 mtorr
0.986923 atm
1000000 Dynes/cm²
232.060 oz/in²
750062 µHg 0°C
0.00647490 tfsi (UK)
0.00725189 tfsi (USA)
1.04427 tfsf (USA)
2088.54 psf (USA)
1019.72 gf/cm²




simple referfence
http://en.wikipedia.org/wiki/Bar_(unit)

gasoline stoich is 14.7.

common misconception.

 

It's really more of a blower thats stacking air in the manifold which serves a similar purpose as compression but its really not compressing.

 

They are actually both correct.

1 atmosphere doesnt equal one bar but they both mean the same thing if that makes any sense.

Atmosphere is actually mathematically correct but has been replaced by 1 bar for practical purposes when it comes to conversions.

 

it does make sense.

im being a goober like usual