Definition
of Cylinder deactivation
With
alternatives to petrol engine being announced ever so often, we could be
forgiven for thinking that the old favorite, the petrol engine, is on its last
legs. But nothing could be further from the truth and the possibilities for
developing the petrol engine are endless.
One
of the most crucial jobs on the agenda is to find ways of reducing fuel
consumptions, cutting emissions of the green house gas, co2, and also the toxic
emissions which threaten air quality. One such fast emerging technology is
cylinder deactivation.
CYLINDER
DEACTIVATION
2.1
CONSIDERING DAIMLER CHRYSLER
By
considering Daimler Chrysler's new 300cc car's powered by a revival of one of
the greatest muscle car engine of all time, the V8 Hemi. This third generation
grand master of funk has a capacity of 5.7litres snorts out 340 bhp with 54kgm
torque and like all Hemis since the early 1950's has a pushrod valve train
rather than a over head cam setup. But even though this Hemi can match its
forebears on power 'its thirst for fuel has been cut by 10 to 20%. It is done
by Chrysler's new multi displacement system (mds).
When
using a lot of power, such as during acceleration, the hemi fires on all eight
cylinders as usual. But around town or when cruising -even at motor way speeds
or under gentle acceleration-the engine switches to frugal four cylinder mode.
Multi displacement system (mds) is activated at part throttle between 1000 rpm and 3000 rpm, when a hydraulically actuated catch in the special valve lifters trips to prevent the valves from opening. Hot gases are trapped in four of the eight cylinders, compressing and expanding like giant air springs as the engine turns over and keeping the cylinder warm. But as long as the valves remain closed, only four cylinders consume fuel instead of eight.
Multi displacement system (mds) is activated at part throttle between 1000 rpm and 3000 rpm, when a hydraulically actuated catch in the special valve lifters trips to prevent the valves from opening. Hot gases are trapped in four of the eight cylinders, compressing and expanding like giant air springs as the engine turns over and keeping the cylinder warm. But as long as the valves remain closed, only four cylinders consume fuel instead of eight.
Engine
efficiency is also improved because the four dormant cylinders are no longer
working hard at sucking air into the engine, something that consumes a
substantial amount of power. Although the average fuel saving is 10% ,under
certain conditions it is a huge 20%.The transition from eight cylinders to four
cylinders happens in just 40 mille seconds under the control of sophisticated
engine management software which controls not just the multidisplacement system
but also a drive-by-wire throttle.
CONSIDERING
HONDA
IN
Japan the 3.0 liter I-VTEC (intelligent VTEC) V6 of the Honda inspire can also
deactivate tree of its first cylinders refinement being guaranteed by active
hydraulic engine mounts to cancel out any vibration and active noise control
with in the cabin to neutralize any unwanted booming. Honda's CIVIC IMA hybrid
also make use of V TEC to deactivate three cylinders on the over run-again to
reduce the pumping losses and cut fuel consumption
CONSIDERING GENERAL MOTORS
The
actual idea of cylinder deactivation is not new. General Motors tried it in
1981 with the V-8-6-4 engine but through lack of sophisticated electronics
drivability was awful. Now GM is returning to the idea again and is to soon
launch Displacement on Demand (DOD} on itsVortecV 8's improving consumption by
between 6 and 8%.
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