Port Minimal CSA 

 A ports minimal cross sectional area, or MCSA is probably one of the most important calculations you can do.  It will show you how close to optimal your heads or head is for the RPM and Cubic inches of your engine. 

Port window entry area

 This is a great calculator for working out the area of the port entry or even plenum opening. Just measure your height and width and radius to see what the port window area is. I quick way to work out the corner radius is with a socket. find a socket that fits the radius properly. measure its diameter and divide by 2 and you have your radius. 

Valve throat Diameter

 Valve throat diameter or % ratio.  This is the diameter usually found at or around the bottom of the seat and you will hear it espressed usually in % of valve daimeter. The typical range for intake valves in between 85-93% 85% being typical OEM manufacturer and 88-92% which a warm engien up to all our race engines. And 92-93% being for extreme motor racing with extremely high piston speeds. Exhaust ratios are usually 1-2% smaller.

Throat Area

A great quick calculator to help with CSA calculations

Estimating Horsepower from Airflow

 This calculator is to estimate horsepower from total induction flow. This figure is usually 3-8% less then head flow figures. The CFM figure needed for this calculator is from one port including all mechanical restrictions, Carby or throttle body and intake. 

Valve curtain area is the area that forms a cylinder shape when we lift the valve open and it gets longer increasing the area as we lift open the valve. 

Knowing and measuring this area helps us understand where the valve no longer becomes the restriction, rather the port does. this is call the Saturation Point.  You can use the next equation to find that point. 

Valve Curtain Area
 
Valve Saturation Point

 This is the saturation point calculator. This is to show at what point the valve curtain area exceeds the ports MCSA. this is where our high speed area that was at the Valve curtain area, shifts to the ports MSCA.  This is where port shape and CSA are everything. And even the smallest porting changes can have huge effects. Now that's not to say port shape  isn't important at lower lifts, it is! Its just lower lifts tend to soften the effect that poor areas in a port can have.

Carby sizing Calculator

An easy to use VE based carby sizing calculator