56 PRODUCT PROFILE
Refined ride quality
A range of innovative hydraulic stops developed by BWI Group enable
many benefits for vehicle ride refinement
VehicleDynamicsInternational.com •November/December 2019
ABOVE: BWI
Group’s Hydraulic
Compression &
Rebound Stops
offer a costeffective
means to
achieve a premium
vehicle feel
in their quest for increasingly refined
ride quality.
Competing designs for end-of-stroke
energy management are available on the
market today, but the designs developed
by BWI Group stand out due to the
smoothness of their engagement and
their tuning flexibility. These features
go beyond the management of so-called
‘spike’ loads that normally occur at the
limits of suspension travel, delivering
additional rebound and compression
damping forces that elevate ride quality
to a higher level.
The HRS system is a well-established
BWI Group design that has proven its
efficiency on a variety of applications,
and it is becoming a standard damping
control feature with some OEMs. The
modularity of the HRS design enables
other features like internal rebound
springs or rebound bumpers to be added,
delivering options for further damper
tuning refinements. Of key importance
›› The damper has a big part to
play in the overall determination
of suspension travel limits, as
it must manage the loads associated
within those limits in both jounce
(or compression) and rebound (or
extension). The effectiveness of the
damper can be increased by installing
BWI Group’s Hydraulic Compression
Stop (HCS) and Hydraulic Rebound Stop
(HRS) systems, which develop additional
damping forces over those provided by
the standard piston and base valves
within the damper. Both these systems
offer efficient dissipation of energy,
improved ride quality, enhanced vehicle
roll and pitch control, and better levels
of noise, vibration and harshness (NVH).
BWI’s HCS damping feature was first
applied to a serial production vehicle in
2018, and a Supplier Innovation Award
nomination quickly followed from BMW,
proving that this new hydraulic feature
provides great value to vehicle engineers
is that each feature can be tuned
separately. Within HRS alone, damping
force gains progressiveness, and the
level of developed damping force can be
tuned to match the vehicle’s ride goals.
The transposal of the HRS principle
into HCS results in a device capable
of delivering a very high level of
compression damping (‘HCS High
Damping’) without influencing the rest
of the damping range. For applications
requiring lower levels of additional
compression damping, an alternative
design (‘HCS Low Damping’) uses a
second position-sensitive valve. HCS
Low Damping gives greater opportunity
for tuning of both compression and
rebound damping at the end of
compression stroke to improve both
comfort and handling.
The coupling of HRS with HCS enables
vehicle engineers to deliver handling and
comfort without compromising either
factor. The additional damping provided
by HRS and HCS not only reduces the
noise transmitted from the suspension
to the passenger compartment, but
also improves the luxury feel of a car
by managing the end-of-stroke energy,
enabling lighter body structures.
While it was initially expected that
the greatest demand for the systems
would come from the heavy electric
vehicle sector, the application of BWI
Group’s HRS and HCS has also been
shown to improve the quality of vehicle
tuning in premium passenger cars. HRS
and HCS could be particularly helpful
for hybrid or electric vehicles based
on existing models, avoiding the need
for major suspension design changes.
These end-of-travel load management
technologies handle the additional
weight of a large battery pack and
will satisfy lower cabin noise level
requirements for electric vehicles by
reducing the road noise transmitted
into the vehicle body. These devices
could also improve the ride performance
of vehicles whose gross weight varies
significantly with payload, as the end
of stroke of the loaded vehicle is better
managed on bumpy or uneven roads.
READER INQUIRY SERVICE
To learn more from BWI Group, visit
www.magupdate.co.uk/pvdi
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