Quote:
Originally Posted by Old Mechanic
tjts1, the 3 liter Porsche 4 cylinder had at least one balance shaft (twice engine RPM), maybe even two. Think the balance shafts were pioneered by Mitsubishi, but there could have been an earlier version.
The problem with 4 cylinders above 2.4 liter is they develop a harmonic porpoising motion from front to back when they go beyond 2.4 liters. Not sure of all the physics involved in that but I know it is generally understood among engine makers.
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regards
Mech
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On the link provided the Continue button goes into great depth about all this.
The link shows there are indeed two countershafts, and that they need to be rotating in opposite directions and talks about the harmonics which never do get solved.
The diesel solutions (cummins, perkins, VW, et al) all turn at pretty low speeds, and tend to be VERY heavy engines. less of an issue at lower rpms.