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A new version of the HKS
four-stroke engine used in Light aircraft, PPC’s and Trikes is now being
delivered in the U.S. In
development and testing for nearly two years,
the new 700E has improved cooling performance and has been further
optimized for pusher applications.
Over 20 airframe manufacturers
worldwide now offer the HKS-700E for their aircraft.
The HKS 700E is a 60HP,
horizontally opposed, two cylinder, four-stroke engine.
The 700E uses a combination of high technology and simplicity to
achieve the twin goals of high power output and reliability. The 700E is a
very high quality product. Every
major component was designed for light aircraft use and is made from the
best materials and techniques available.
In power to weight ratio, the
700E matches conventional two-strokes.
The real difference, however, is in the high peak torque (50.6ft.lbs@
5000 RPM)
of the engine and the very flat torque curve.
This allows the 700E to pull better in a climb or hold a higher
prop load (pitch) than the 60 horsepower rating would suggest.
The integral gearbox on the 700E
uses straight cut gears with a spring-washer type torsional coupling ahead
of the large flywheel. The
gearbox is attached to the flywheel case; the gears are lubricated by the
main engine oil system, the same as a Rotax 912 four-stroke.
The gearbox can be run up or down and is changed by rotating the
flywheel case around. The
large flywheel mass and attention to the internal balance of the engine
are the keys to the smooth running and low vibration of the 700E. At a lower RPM you can hear the gears singing, not
clattering. The standard gear
ratio is 2.58 to one. As the Max permissible RPM is 6200, the RPM at the
prop is 2400. With the
optional 3.47 to one gearbox, the prop speed and noise is even lower.
The prop hub bolt pattern
is the popular 75MM pattern; the direction of rotation is the same as a
Rotax two-stroke. HPower has
conducted baseline tests of several popular propellers, including the Ivo-prop,
Power-fin and Sport props. In
tests, the 700E can swing a 74” two blade and a three blade 68” was
typical. The engine was just as smooth with a two blade prop as three.
This also allows the use of a light, wood two-blade for certain
applications.
The induction system of the 700E
has been optimized for a wide torque band. The runner lengths are tuned
for this purpose. The
carburetors are the Bing Constant velocity type, which varies the mixture
with horsepower and provides a modest amount of altitude compensation.
These are the same carburetors used on the Rotax 912 four-stroke.
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The valve train of the 700E is
operated with pushrods off of a single, centrally located camshaft; valve
lash is adjusted automatically with hydraulic lifters.
The crankshaft and connecting rods are forged, and run in split
shell-type bearings. During
overhaul the crank and connecting rods won’t have to be replaced, just
the bearings. The cylinder
bores are Nickel-ceramic coated for wear resistance and thermal
compatibility with the expansion of the piston.
The dual CDI (Capacitive
Discharge Ignition) is a programmed smart type that varies the timing for
ease of starting, smooth idle and detonation resistance. The connectors to the electrical system are large sealed type
and can only attach to the correct component.
The charging system is 15 Amp-180 Watt.
The exhaust systems that are provided in the complete packages are
beautiful. Made from highly
polished stainless steel, they come in four configurations (two manifold
types, two mufflers) and can be modified with optional stock components.
HKS is a big producer of performance exhaust systems for all types
of cars and their expertise clearly shown in the design and fabrication of
the manifolds and the mufflers.
HPower has been testing the 700E
on a Flightstar-IISL testbed since July‘97 and the results have been
impressive. The engine has
been easy to start, very fuel efficient and reliable in operation. The range of the Flightstar-IISL was effectively doubled with
the switch out of the standard 503. The
fuel specifics sent from Japan indicated a fuel burn higher than we
achieved in our testing; the factory spec is based on a constant peak
torque load while dyno testing. This would be the equivalent of a very
high pitch prop and full throttle. Our testing with typical, fixed pitch
propellers showed an average fuel consumption of between 2 and 2.5 gallons
an hour at typical cruise settings.
The installation requirements are
different for a four-stroke engine and HPower is here to help with the
choice of components and the design of mounting system. HPower can supply you as well with the proper accessories
like oil lines and fittings, instruments and service parts.
We have done a lot of research on the various components available
and are planning to be a worldwide leader for HKS 700E specific equipment.
The 700E comes from HKS with
detailed Installation and Operation manuals.
A Parts manual
as well
as an Operations and
Installation
manual are available.
Pricing
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