Abstract
This paper discusses a theoretical phase-control design strategy for idle shake affected by an
arrangement of a powerplant on transversely mounted Front engine Front Wheel Drive
(FWD) passenger cars. There are two types of powerplant arrangement for FWD cars
heading up to the North in the top view. One of them is a typical "east-west arrangement",
which allows the "front" of the engine to be placed to the right or "east", and the "rear" of the
engine that is to mate to the transmission to be placed to the left or "west" (Fig.1). Another
one is "west-east arrangement", where the engine is positioned to "west", and the transmission
is positioned to "east" (Fig.2). In general, a dynamic damper like a radiator supported by a
rubber bush built in the front end of the engine compartment is widely believed to reduce a
gain of FRF (Frequency Response Function) at resonant frequency. In addition to that, it
becomes clear in this paper that the dynamic damper has an additional phase-shift effect
between the two FRFs. That is to say, the two vector responses of the body vibration caused
by the two excitation forces, which are the roll moment and the vertical force of the engine,
cancel each other and the resultant vector becomes so small. In this manner, the powerplant
arrangement affects idle shake deeply correlating with the phase-control design.
A combination of the East-West arrangement and a 2nd order balancer-less engine is the best
design for idle shake of the 2nd order harmonics. On the contrary, a combination of the West-East
arrangement and a balancer-less engine is the worst design. If the engine is equipped
with 2nd order balance shafts, idle shake is estimated to be middle between them, regardless of
the powerplant arrangement.
Keywords - idle shake, East-West, dynamic damper, vector, phase