Engine Math

Hello Reader(s)


One of my goals in life is to build engines. I would like to learn how to modify engines to be both more powerful and efficient.

One car that is very iconic in my mind is this mid 1990's honda civic.

Photo from the ad

The car has a motor Honda produced for fuel economy. The owner decided that instead of swapping the anemic but efficient motor with one of many engines a person can put in a civic (the last time I check the number was 7 different engines) he would modify the fuel efficient 1.5 liter motor.

The result is a claimed 228 hp, where the motor probably had 60 to start, and a claimed 55mpgs.

I am a big fan of math as a way to interpret the world around us. My goal is to take this same mindset with me to engine building.

I use this compression ratio calculator all the time as I dream of putting the engine together I have in various parts around my parents house.

I need some advice though on volumetric efficiency. This site states that the equations is


VE= (3456* cfm)/(cubic inch displacement*rpm)

Does this seem valid?

I will add more content on this topic as I gain more experience.

Also here is a good write up on the mechanics of a four stroke motor.