The Workhorse ZDZ 210 good for 3.3 YAK, and 50% Cub
ZDZ engines have rotary valves*. This is
one of the main reasons for the incredible throttle response of ZDZ RC gas
engines. Most engineering experts agree that the rotary valve has brought
the two-cycle engine its highest degree of efficiency and performance.
Available in 40CC to 420 CC sizes
- All ZDZ engines that use a rotary valve with fixed induction timing
must use a unique starting procedure as compared to their piston
ported or reed valve inducted counterparts.
two cycle gas engines require a mechanism to close off the carburetor
from the crankcase during part of the cycle. A number of methods have
been developed by two cycle engine designers. The most popular, only
because it is inexpensive to make, is the use of a metal reed that
closes the opening to the carburetor when the pressure in the
crankcase increases. This method works well at low engine RPM, but has
problems permitting enough fuel to enter at the higher RPM
ranges. The Rotary Disc Valve is a thin steel disc that is attached to
the crankshaft and by the means of slots cut in the disc alternately
opens and closes the opening to the carburetor. The opening is
designed to produce an even idle, instant throttle response AND a wide
throttle power band. ZDZ® began using reed valves but has
since modified or designed their newer engines to use Rotary Disc
valves. A significant increase in engine performance was thus
achieved. The inline ZDZ® engines and the quad 160 cc
still use reed valves, as there is no practical method to incorporate
a Rotary Disc Valve in these engines.
weight design Simple answer; by design. The ZDZ®
cylinders and crankcases use investment castings designed with
both strength and lightness in mind. The cylinders walls are plated
with Nikasil, a space age concoction of microscopic Silicon Carbide
granules held together by a matrix of Nickel. Silicon
Carbide provides the harness and Nickel the slipperiness.
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