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NAVC Hybrid Transit Bus Certification
Workgroup
The
range of in-use hybrid engine data is best represented by the Euro
III steady-state cycle among existing steady-state test cycles.
Although the engine in a hybrid-electric bus configuration, by virtue
of its coupling to the generator, cannot follow the FTP, it is understood
that engines certified for hybrid-electric bus application using
the proposed EURO III criteria would meet truck emissions standards
if decoupled from the generator and subjected to the FTP certification
test. The Euro III is widely recognized by engine manufacturers
and regulators, therefore allowing for an easy and quick implementation
of a special test procedure in the near term to serve as an interim
engine certification procedure for engines in hybrid-electric urban
buses.
In
order to certify any engine for use in a heavy-duty hybrid application,
one of two options could be pursued. The first and most straightforward
is to certify the engine on the FTP to the urban bus standard. FTP
may be an appropriate test cycle for (some) hybrid-electric bus
engines, but a steady-state cycle may be more indicative of engine
operation and consequently should be considered for EPA certification.
Thus the second option, provided the engine application precludes
its being tested on the FTP, is to take advantage of the special
test procedures provision included in 40 CFR 86.090-27.
In
order to use the special test procedure provision, however, it is
generally accepted that the engine should not be able to operate
on the FTP. As noted, engines in hybrid-electric applications closely
mimic steady-state operation, and of the available test cycles,
the one that seems to be the most appropriate is the Euro III 13-Mode
Test Cycle. The NAVC Workgroup recommended its use as an interim
engine certification for series hybrid heavy-duty buses, with a
sunset date of 2004. The complete recommendation was published in
a September, 2000 report entitled "Engine
Certification Recommendations Report."
Chassis
Testing
The Workgroup
is also working on chassis testing for heavy-duty hybrids. The Workgroup
agreed that it would be beneficial to industry and regulators to
have a chassis testing standard developed. To that end, the group
has been working with the Society of Automotive Engineers (SAE)
to develop a recommended practice for heavy duty hybrid chassis
testing. The Workgroup hopes to have a recommended practice issued
in early 2002. For more information on this activity, contact Lisa
Callaghan at 617-482-1770 ext. 14 or by email at lisacal@navc.org.
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