Useful calculations in the construction of a 2T engine

We share some of our research we did in building our Derbi engines.

Here are some formulas that can help you in the preparation of your engines.

Calculate cylinder volume:

• VC - Cylinder volume
• R - radius of the cylinder
• C - cylinder stroke
• Π - Pi (3.14)

Formula:

VC = Π x r² x C

If you have a crankshaft with 40mm stroke and a piston with 42mm diameter, you will have the following displacement:

VC = 3.14 x 441 x 40 = 55389mm³ / 1000 = 55.38cc³

Calculate the compression ratio:

• C - Compression rate
• VC - Volume compression
• VVC is the volume of the compression chamber

Formula:

C = (VC+VVC) / VVC

If you have a compression volume of 55.38cc³ and a compression chamber volume of 5.27cc³ you will have the following compression ratio:

C = (55.38 + 5.27) / 5.27 = 11.50:1