 It takes the carbs air velocity (which is reduced if there´s a needle jet) and half of the squish velocity and adds them together and from that it calculates a needed oil viscosity at the most common upper cylinder temperature which is 175 celsius. Then it shows you which premix oils are within 7% of that viscosity so you are free to choose one of them. At the needle jet the higher the air velocity, the more the fuel becomes atomized (the droplets become smaller in size). The more atomized the fuel, the quicker it burns but each engine needs a certain amount of atomization since the ideal burn extends till the exhaust port opens. Only the squish velocity needs to increase with an increase in top RPM. Its bar graph is visually helpful. It shows if the air velocity due to carb size is too high or too low, whether the squish velocity is too high or too low, whether the combined velocities are too high or too low (compared to an average), and then compares your chosen oils viscosity to the ideal viscosity and shows if it is too high or too low. Of course you can then chose to modify your squish velocity rather than give up the oil you have wet dreams about (just kidding, but seriously lots of riders are emotionally attached to their favorite oil). In this example the chosen oil has a 2.61 viscosity and the ideal oil should be 2.77 and so the graph shows that the chosen oil has a viscosity that is 6% less than the ideal. C5 reads the squish velocity from the squish calculator but if the head doesn´t have a squish band then you can enter 0.1 at F6 and it will override what is at C5. Also if you know the squish velocity from using a different calculator then you can enter that value at F6 for it to override C5. |