IN THE EARLY days of emissions controls, we ran a droll cartoonshowing
a clean air car sucking in smog and emitting crystal-clear exhaust.
Well, guess what? Honda's ZLEV technology, announced at the 1997 Tokyo
Motor Show, is very much along these lines. The letters stand for Zero-Level
Emissions Vehicle; and, to avoid possible confusion in our
clean-air alphabet soup, here's Honda's definition: A ZLEV's emissions
are the same as those emitted by a state-of-the-art electric utility when
the latter is producing the power to propel an electric vehicle the same
The relevant pollutants are carbon monoxide (CO), the nitrogen
oxides (collectively, NOx) and the non-methane organic gases (NMOG). These
last, by the way, are the hydrocarbons (collectively, HC) that actually
contribute to smog.
To put ZLEV numbers in perspective, they're typically less than 0.10
of Ultra Low Emissions Vehicle standards, hitherto the lowest promulgated
for internal combustion engines. What's more, this is the first time I've
seen a quantification of emissions from "Zero" Emissions Vehicles, or ZEVs,
when the remote emissions of the electric utility are factored in -- as,
of course, they should be.
That is, as I noted a while back, ZEVs would be more logically called
REVs, Remote Emissions Vehicles. On the other hand, our clean-air alphabet
soup recipe is complex enough as it is, so I rather doubt my suggestion
will catch on.
Honda dernonstrated this new technology in a most astounding manner.
I got to drive one of the ZLEV cars at its Tochigi, Japan, R&D facility.
Its operaüon was utterly transparent, with exemplary driveability
and good power. In particular, even on light throttle, 1 sensed no lean-burn
hunting whatsoever. A perfectly normal Honda.
Then the car was brought into the emissions lab, hooked to the analyzer
and run through the final portion of the U.S. Federal Test Procedure.
Its NMOG for instance, were around 0.5 parts per million; sure enough,
equivalent to 0.10 ULEV level. Next, engineers removed the sensor from
the ZLEV's tailpipe and exposed it to the lab's ambient air. The NMOG level
in the lab measured around 1.6 ppm; quite clean, really; about half
of a typical Los Angeles ambient reading -- but also more than three tinies
dirtier than the ZLEV's exhaust.
Literally, ZLEV operation imitates that R&T cartoon in cleansing
ZLEV technology is an iteration of Honda's existing ULEV practice.
A 32-bit Electronic Control Unit gives extremely precise control
of the air/fuel ratio. A series of catalytic converters operate at especially
high efficiency. And Honda's VTEC variable valve timing hardware plays
an important role as well.
lt's a three-stage strategy. First, in cold start, VTEC induces a marked
swirl of the incoming charge to reduce unburned HC. Any HC that is
produced gets absorbed downstream on one layer of an innovative dual-bed
catalyst. Second, during warmup, the converter residing immediately next
to the exhaust manifold quickly reaches its operating temperature. In the
meantime, farther downstream, the HC is "de-absorbed" and treated as the
threeway portion of the dual-bed catalyst heats up. The gases then travel
into an Electrically Heated Catalyst directly downstream of the dual-layer
device. The EHC's operation is optimized for highly efficient treatment
of this remaining HC.
Third, in normal Operation, the advanced 32-bit Electronic Control
Unit offers two benefits in engine management. Emissions are reduced at
the source through a more stable combustion process. And an extremely precise
control of the air/fuel ratio provides "feed gases" that keep the converters
operating in their most efficient range.
It's noteworthy that Honda's ZLEV technology is essentially evolutionary,
not particularly radica1. Also, this is an ordinary car burning gasoline,
not some exotic alternate fuel.
About two years ago, I drove a prototype of Honda's ULEV Accord. It's
now available in selected U.S. markets. Expect a similar lead time for
IMA, an electronic turbo
THE SECOND MAJOR innovation shown by Honda at Tokyo was its IMA, Integrated
Motor Assist. This hybrid powerplant combines a 1.0 litre 3-cylinder VTEC
Gasoline Direct Injection engine, an electric motor/generator linked to
in ultracapacitor, and a continuously variable drive.
It's a parallel hybrid, with each power source contributing to propulsion
on demand; this, as opposed to a series hybrid, where one power source
feeds the other, which, in turn, drives the wheels.
In fact, think of the IMA as a small displacement gasoline engine augmented
by electric supercharging.
An ultracapacitor is a largish
condenser, an electrical device storing its charge between internal plates.
The IMA´s ultracapacitor array is about the volume of a Suitcase
-- decidedly smaller and lighter than any EV battery pack. On the other
hand, it's purely for intermittent use: IMA's fully charged gizmo offers
perhaps 13 seconds of boosted operation.
The IMA's high efficiency comes from several interacting strategies.
Honda's integrated Motor Assist sandwiches a high torque electric
motor between its direct-injection gasoline engine and CVT gearbox.
The result is 70 mpg in Japan city mode testing.
First, under light load, the gasoline engine and CVT operate in regimes
of GDI lean-burn high efficiency. (For details of Gasoline Direct Injection,
see "Technology Update: The Last Internal-Combustion Engine?" December
1997.) VTEC promotes this light-load combustion with high-swirl-inducing
valve timing. Also, the small displacement of the IMA engine translates
into reduced frictional and pumping losses.
Second, gradual demands for power are met essentially by the gasoline
engine alone, its VTEC valve hardware changing over to optimize engine
performance at higher revs.
Third, to invoke immediate power, IMA calls on the ultracapacitor.
Its charge is routed to the electric motor/generator nestled between the
engine and CVT. This DC brushless motor is derived from Honda EV Plus technology.
Also, its controller is programmed to invoke a subtle reverse torque on
the gasoline engine's output, thus reducing torque fluctuation of its configuration.
Fourth, in braking, the motor/generator operates regeneratively, charging
the ultracapacitor for its next boost.
What's more, all this hybrid activity happens essentially transparently
to the driver. I had an opportunity to tool around Tochigi in an IMA powered
Honda Life city car and can report that an "Assist" light on the dash was
the only way I could sense any transition from gasoline power to ultracapacitor
Honda says the basic gasoline engine produces some 70-80 bhp, with
the electric motor contributing another 50. The entire package weighs
about 110lb. more than a conventional 1.5-liter powerplant, this
latter actually yielding somewhat less performance. Also, the IMA's control
strategy is designed to optimise the high rpm power of the VTEC GDI engine
with the high torque available from an electric motor on demand.
An important benefit is IMA fuel efficiency (and hence its reduced
CO2 production). Fuel economy is said to be better than 70 mpg on the Japanese
city mode test. The IMA package is part of Honda's J-VX sports coupe exhibited
at Tokyo (see Ampersand). This hybrid technology is likely to appear on
the roads of Japan within two to three years and here as well in time.
At Honda, the theme was "Small is Smart." And this 2+2 JV-X concept
car looks smart indeed, sort of a CRX for the next millenium. Beneath the
hood of this California styled front driver is a totally new power unit,
a lightweight, clean-burning, direct-injected, VTEC-aided 1.0-litre inline-3
that has an ultrathin motor/generator mounted between it and the continuously
variable transmission. This motor/generator serves as an extra power source
for the JV-X when it's accelerating. Honda says that, thanks to IMA (the
Integrated Motor Assist system), the JV-X accelerates like it has a 1.5-litre
engine rather than a 1.0.
IMA also helps make the JV-X's fuel economy excellent, a heady
70 mpg. Under braking and deceleration, the motor/generator transforms
kinetic energy into electric power. Of note, the electricity is stored
in (and quickly released from) huge capacitors, which weigh 66 lb.