Quote Originally Posted by rar110 View Post
Why is a 5 cyl smoother, and is the 60 degree v6 configuration help? Thanks.
It's an angular thing ... getting beyond my field of technical expertise.

Taking electronic control into account (like the Td5 cylinder balance) gives engines far more chance of being smoother without the use of counter balance shafts, etc ...

These two links explain it better than I can ...

https://en.wikipedia.org/wiki/Straight-five_engine

Quote - A five-cylinder engine gets a power stroke every 144 degrees (720? ? 5 = 144?). Since each power stroke lasts 180 degrees, this means that a power stroke is always in effect. Because of uneven levels of torque during the expansion strokes divided among the five cylinders, there are increased secondary-order vibrations. At higher engine speeds, there is an uneven third-order vibration from the crankshaft which occurs every 144 degrees. Because the power strokes have some overlap, a five-cylinder engine may run more smoothly than a non-overlapping four-cylinder engine, but only at limited mid-range speeds where second and third-order vibrations are lower.

... add ECU control and cyclinder balancing achieves a reduction or removal of the "ordered" harmonics that are noticeable.

The Physics of Engine Cylinder-Bank Angles - Feature - Car and Driver