FHPCurve

The friction (also called the 'friction horsepower' of the engine is the power absorbed by the friction of the engine when it is turning. All experience shows that this increases with the square of the rpm. So using the method you've learned, you edit these data points to produce a smooth curve.

And here's a smooth friction horsepower curve.

The friction data points are the intersection of the power data lines with the vertical chart axis at 0 rpm. When you edit these points, Benchmark adjusts the horsepower of the HP1 and HP2 data points, using the maximum manifold pressure point as the center of the rotation of this line. Thus, it's always best to smooth out the maximum manifold pressure curve as a first step.