Take a 350 V8 as an example, say it uses a .500 lift cam where at .400" valve lift the cylinder head flows 200 cfm, the HP formula would then look like:

200 x .257 x 8 = 411 hp

Now, if we were desired a 575 hp engine we could deduct the 411 hp from the 575 hp, like so:

575 - 411 = 164

Then take this number and divide it by 14.7 to get the required Boost PSI, like so:

164 / 14.7 = 11.15 Boost PSI

Is this process already known w/in the turbo/supercharger crowd or am I on to something.

Let us take this same 350 V8 and let us say we wanted 650hp from it and were going to ust AFR heads and a cam whose profile had a peak valve lift of .600" lift; and the .500" lift flow value was at 250 cfm.

250 x .257 x 8 = 514 hp normally aspirated

650 - 514 = 136

136 / 14.7 = 9.2 Boost PSI required

 

Not sure where you got your calc for horsepower but its no correct and there are many other variables invovled.

As for your required boost calc, the hp differential has nothing to do with stoichiometric efficiency. Required boost is calculated based on displacement, flow, and amount of fuel injected per timing event.

 

found it on an other site, i was looking up soemthing else and came across this.

i have never done any turbo calculations. just cuttin an pasting. good to know it's wrong. some one might have made a mistake

 

here ya go

https://www.dieselbombers.com/general-diesel-related-tech-articles/4693-turbo-101-a.html

https://www.dieselbombers.com/general-diesel-related-tech-articles/4697-turbo-systems-102-advanced.html

 

Both of these links have excellent information. If you guys want to learn the intimate details behind calculating turbo requirements the second link is really good. Thanks ya Mr Whit.

 

Keep in mind that these calculators are only accounting for the very basic and crude data and are used to give you a very rough estimate as a starting point. You have to know your flow rates and volumetric efficiency through the intake system, charge air system, and fuel timing throughout the curve before you can even get close to an accurate calculation. Turbo boost vs horsepower is dependent upon the engine design, flow rates, and fuel timing. Also, keep in mind that horsepower is a derivative of torque and not the other way around.

 

its above my head.................