[Tom McQueen]

Assuming its do-able with numbers, Im looking for a math formula to determine max boost. If the centrifugal's output is 1850cfm, the engine is 555ci and the max rpm is 6500rpm, what is the boost at 6500?

Here is my best guess. operative word is guess.

A 555 spinning 6500 rpm requires 1043cfm.

ci / 2 X rpm / 1728 = cfm

If you force an additional 807cfm into the motor, thats 77% more air over atmosphereic pressure (14.7).

14.7 X .77 = 11.32 psi boost.

OK. Show me where I went wrong. Is it really this straight forward?

[aasmilyy]

i find this under boost links, maby this will help you

http://www.stealth316.com/2-turbotemp.htm

[GoatRider]

Hey neighbor!

I think two major factors you need to input into your math are:

1- Base the "more air forced in" ratios on mass(lbs/min) rather than volume(cfm) which in turn forces you to take into consideration:
1(a) - Temperature, the compressed air will be hotter than the 14.7psi "atmosphere" air.

2- Volumetric Efficiency of the intake/head/valve timing/exhaust "package." I believe the general idea of 1.77 x atmospheres = 1132 lbs of "boost" only works if the VE of the engine is right around 100%.

I bet someone like Tom Vaught has the awesome Excel spreadsheet or other software that will do just what you want to know...

[Tom McQueen]

For this exercise Im mostly ignoring temp rise. Pick a temp. 90 degrees works for me. I do have the largest air to air intercooler Garrett makes, so hopefully that keeps the pressurized side temp close to ambient. It makes sense to use volume. Ill see how that computes.


Heres an observation Ive recently made. It has to do with compressing air and temp rise. I have been taking daily Hyperbaric Oxygen treatments (HBO2) for the last month. They seal me inside of an acrylic tube and run the pressure up 2 atmospheres. Then they pump 100% oxygen into the sealed tube. I then lay there for a couple of hours contemplating my naval and once the 2 hour time period is up, they de-pressurize and I come out. In the beginning, during the pressurizing stage, its warm. Not hot, but there is a very noticeable temp rise. And during de-pressurizing it gets pretty chilly. Ive always heard about the temp rise of compressing air. Never thought I would experience it first hand.

Found what I was looking for here;

http://www.rbracing-rsr.com/calcboost.html

[bryansMtngto]

think you need to consider the blower ratio rpm as well when figuring its cfms output. or did you calculate the blower cfm of 1850 for that rpm?

[Tom McQueen]

Its a Procharger, rated to deliver 1850cfm @ 74,000rpm. Im just using their numbers.

The boost calculator I found at RBracing put the max boost in the 16# range on my setup. More than good.

[bryansMtngto]

ok was just wondering cause i know when we were figuring out a blower for my combo it came into the figures. Since your using their numbers that should be already figured in the cfm number.