This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Electronic Valve Control System for High-Performance Engines
Technical Paper
97A057
Sector:
Language:
English
Abstract
The strategic potential of variable valve actuation (VVA)
technologies for performance and fuel economy improvement has been
widely recognized since the early beginning of the internal
combustion history. The R&D efforts have been mainly devoted
until recent years to develop ingenious mechanical devices to vary
the valve timing as a function of engine speed (first generation
systems) or to modify also valve lift, even if in a limited range
or in a stepwise manner (second generation systems).
More recently third generation systems have been envisaged,
capable of fully exploiting the variable valve concept potential
through a complete and highly flexible electronic control of the
valve opening laws (EVC).
An EVC system based on the electro-hydraulic actuation concept
is under development, with the target to verify the expected
advantages in terms of performance and fuel consumption on
spark-ignited engines and to demonstrate the industrial feasibility
for mass production at a reasonable cost.
The possibility to maximize the trapping efficiency over the
entire speed range, to operate the engine unthrottled and to
control the inlet air stroke-by-stroke and cylinder-by-cylinder has
been demonstrated, resulting in a substantial improvement of power
and torque density up to 25%, while reducing fuel consumption by
15% on the NEDC driving cycle. Further gains in fuel consumption
could be achieved through transmission rematching and cylinder
deactivation.
Extended consistency and durability tests are in progress, in
order to fully demonstrate the robustness, the reliability and the
industrial feasibility of the system.
If successful, this technology could be extended to other
applications, such as engine braking on heavy-duty diesel
engines.