Horsepower vs pounds of air

The first thing we must understand when building any engine is, just how much air the engine will see for a given horsepower value. This calculator can help with that and we are using the more accurate pounds of air rather then CFM (Cubic feet per min)

BSFC is  Brake Specific Fuel consumption. 

As the acronym states, its related to fuel consumption or rate of fuel flow needed to produce each horsepower. 

Here is some average BSFC for different types of induction using gasoline. 

NA BSFC = 0.45-0.50
Supercharged BSFC = 0.55-0.60
Turbocharged BSFC = 0.60-0.65

Horsepower to pressure ratio

Another great calculator to help you work out just how much boost your engine will need to make your targets.  Using the data from the previous calculator, we use Pounds of air instead of HP as we can use this data to understand Turbocharger flow maps,  what Pressure ratio we will need and it will give us a good understanding of how our IAT's (Intake Air temps) play a major roll in the outcome of your final result as our Intake temps effect the molecular mass (density) that is available. Hot gases have less density so have less molecular mass which means less available oxygen. 

This calculator will also hopefully help you understand just how important our base NA 

(Naturally aspirated) VE's is and the compounded effect it can have on every extra Atmosphere we add to the system. 

Air flow is in Ibs/min 

IAT's are in Fahrenheit

VE's Volumetric Efficiency is a % of how well the engine fills its cylinders. 

An early push rod engine will be around 80% (gen 1 chev) some later push rod engines like the LS1 (Gen 3) will be around 90%. 

With over head single cam 2 valves per cylinder we are around 88% and modern twin cams are as good as 95%. 

Engine size is in Cubic inches.

Remember this calculated result is in Absolute Pressure so we must subtract our 14i.7psi of Atmospheric pressure. Also we must be aware that our Atmospheric pressure is relative to elevation. As at 10,000 feet above sea level our Atmospheric pressure is only 10.1psi. 

Estimating Horsepower losses with Elevation

This is a great little calculator to estimate just how much Horsepower you loose going to elevated areas and really high lights why low salt lakes are to go to for land speed records. Density is everything! 

Elevation is in feet