The current spark ignition (SI) Duke engine offers the potential to operate on all
of the alternate fuels generally considered suitable for a conventional SI engine
with little or no development. "Bio-fuels" are alternative fuels derived from
vegetable feedstock that can be formulated to provide a basis or blending
component for many of the alternate SI and Compression Ignition (CI or "Diesel
Cycle") fuels, the most common being bio-diesel (for CI) and bio-ethanol (for
SI).



The Noise, Vibration and Harshness of an engine are not only important from
an engineering perspective but impact on the entire system of which the engine
is just a part. The Duke Engine offers outstanding positive NVH benefits.

Mechanical forces from rotating and reciprocating systems in the axial
arrangement of the Duke engine are very different from any conventional
engine. The sinusoidal reciprocating force from each cylinder combined with the
inertial forces from the nutating body sum up to leave a simple first order
balance couple, which can be fully resolved using basic fixed masses on the Z
crankshaft. The Nutating reciprocator leads to very low angles of con rod
articulation (<3Deg deviation from cylinder axis) resulting in near sinusoidal
reciprocating motion, meaning there are negligible secondary or higher order
vibration forces generated within the reciprocating system. This is in starr
contrast to conventional engines where unresolved second order vibrations can
dominate the mechanical vibration levels, as in the case of a conventional in
line 4-cylinder engine. Many conventional 4-cylinder engines are fitted with twin
balancer shaft systems driven at twice engine speed to enable such engines to
meet market acceptance levels.

It is reasonable to say that the mechanical balance of the Duke Engine is near
perfect, without the added complexity of additional balance shafts etc.