From where is this number

Hello, Ben!

I have a question where you took a number 120?

When you divided it on RPM?

Thank you for your work!

Good luck!

Hi Nick and sorry for the slow reply. This is just a very simple way to convert from engine rpm to cycle time. Let's go through a quick calculation so you can see where it comes from:

Let's assume we're operating at 6000 rpm.

First we need to divide 6000 by 60 to convert to rpm per second - 6000/60 = 100 rev/s

Next we need to convert rev/s to cycles per second. Remember there are 2 revolutions per engine cycle so 100/2 = 50 cps.

We can skip the interim step by just dividing 6000/120 to get the same result which gives us 50 cps. If we instead divide 120 by 6000 we get the cycle time of 0.02 s or 20 ms.

Does that make sense?