Evolution Engines 20GX 20cc - Manual (Page 4)

4 5
Introduction
Congratulations on your purchase one of the exciting new engines in the Evolution ® small
block gas engine series. All of the Evolution brand gas engines are designed from the start to
provide you with excellent performance at a fraction of your previous operating costs. We have
painstakingly designed and tested each engine to ensure a hassle-free experience without
giving away anything in expected performance or durability. This manual, when read and
followed, will guide you through the simple steps to your success. Welcome to the Evolution
family.
Small Block Gas Engine Design
Starting with our already proven glow engines enjoyed by thousands around the world, we
endeavored to take that excitement and experience into the realm of gasoline fuel to provide
you with a complete package; great performance and low cost of operation.
Step 1 Start with a great engine. The Evolution glow engines have provided thousands of users
excellent performance.
Step 2 Design a new carburetor system that will be reliable and provide for hassle-free use by
the owners. This new carburetor, with already proven technology, was modified to fit in
the available space in front of the cylinder and the unique needs of a gasoline fueled
engine. Built onto the front of the carburetor is a fuel-pressure regulator. On the back of
the carburetor is a new crankcase-driven pump. This pump helps maintain constant fuel
pressure as well as draw fuel to the carburetor. A new cat’s eye style fuel metering system
was added to allow for more controllability to the low and mid-range throttle positions.
Step 3 Design the proper muffler system to handle the extra heat and expansion of the burnt gas
mixture when compared to a glow system. We decided to include an inverted wraparound
muffler that would make a more compact and clean installation. We also repurposed the
fuel pressure nipple and utilized this for a smoke inlet for those users who would like to
have smoke on-board their airplane. The new dual exhaust outlets provide a deeper yet
quieter sound.
Step 4 Design operating accessories that enhance the user experience. During our extensive
2 1/2-year testing program we discovered a lot of new techniques and obstacles that are
unique to gasoline fueled small block engines.
• Because the amount of fuel consumed is one third that of a comparable sized
glow engine, the construction and reliability of the fuel delivery system to the
carburetor becomes three times as critical. Microscopic pieces of dirt that
used to safely pass through the larger fuel passages of a glow carburetor will
wreak havoc on a gasoline system.
The same holds true for air bubbles from the tank or any small leak in the fuel
tubing; what would pass harmlessly through a glow carburetor simply is not
tolerated in a gasoline system because the air bubbles are effectively three
times the size they used to be. We have sourced an excellent sintered plastic
clunk that, when used in the tank, stops all air bubbles in the fuel line as
well as filters out any dirt in the fuel system. The included clunk is critical to
ensuring successful and reliable operation.
• We found that high temperatures destroy normal Tygon ® tubing (the go-to
choice for gasoline engines) within minutes. We found that Neoprene tubing
would withstand the temperatures but it tended to degrade quickly in use. We
recommend using FKM or Viton
® tubing in your fuel system plumbing. FKM
tubing is specifically formulated to withstand high temperatures and harsh
petrol-based chemicals, such as gasoline.