Numerically Integrating Engine P-v diagram

I am currently trying to find the net work out of an engine power stroke by numerically integrating a pressure vs volume diagram I have made. Currently, I belive the trapz function is not finding the net area/not subtracting the area as the integration sweeps back to towards the starting point since the value I am getting is much higher than my calculation using Mean Effective Pressure. Is there a easy way to numerically integrate to find net/enclosed area? Thanks!

p0apsi=p0a.*bar; %pressure 0 advance in psi

power0a=(trapz(V,p0apsi))/12; %net work out [ft-lb]

output:363.5378

MEP Calculation: 275.5214

[David Goodmanson]

HI Evan,

Is the squished ellipse at the bottom of the plot an intentional part of the cycle?

[Daniel Dos Santos]

I believe that it is