O.S. Engines 21VZ-R Turbo II - Manual (Page 5)

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Since the compatibility of glowplug and fuel may have
a marked effect on performance and reliability, it may
be worthwhile to choose the R/C type plug found
most suitable after tests. Recommended O.S. plugs
are P7. Carefully install plug finger-tight, before final
tightening with the correct size plug wrench.
GLOWPLUG
The role of the glowplug
Glowplug life
Particularly in the case of very high performance
engines, glowplugs must be regarded as expendable
items. However, plug life can be extended and engine
performance maintained by careful use, i.e.:
Install a plug suitable for the engine.
Use fuel containing a moderate percentage of
nitromethane unless more is essential for racing
events.
Do not run the engine too lean and do not leave the
battery connected while adjusting the needle.
With a glowplug engine, ignition is initiated by the
application of a 1.5-volt power source. When the
battery is disconnected, the heat retained within the
combustion chamber remains sufficient to keep the
plug filament glowing, thereby continuing to keep the
engine running. Ignition timing is 'automatic' : under
reduced load, allowing higher rpm, the plug becomes
hotter and, appropriately, fires the fuel/air charge
earlier; conversely, at reduced rpm, the plug become
cooler and ignition is retarded.
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Apart from when actually burned out, a plug may
need to be replaced because it no longer delivers its
best performance, such as when:
When to replace the glowplug
Filament surface has roughened and turned white.
Filament coil has become distorted.
Foreign matter has adhered to filament or plug
body has corroded.
Engine tends to cut out when idling.
Starting qualities deteriorate.
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TOOLS, ACCESSORIES, etc.
FUEL
Generally, it is suggested that the user selects a fuel
that is commercially available for model two-stroke
engines and contains 10-30% nitromethane. As a
starting point, we recommend a fuel containing 20%
nitromethane, changing to a fuel containing more nitro if
necessary. When the brand of fuel is changed, or the
nitro content increased, it is advisable to repeat the
running-in procedure referred to in the RUNNING-IN
paragraphs.
The following items are necessary for operating the
engine.
REMINDER!
Model engine fuel is poisonous. Do not
allow it to come into contact with the eyes
or mouth.
Always store it in a clearly
marked container and out of the reach of
children.
Model engine fuel is also highly
flammable. Keep it away from open flame,
excessive heat, sources of sparks, or
anything else which might ignite it. Do not
smoke or allow anyone else to smoke,
near to it.
Please note that with high-nitro fuels, although power
may be increased for competition purposes, glowplug
elements do not last so long and engine life will be
shortened.
BATTERY INTEGRATED GLOWPLUG HEATER
Commercialy available handy glowplug
heater in which the glowplug battery
and battery leads are integrated.
FUEL PUMP
For filling the fuel tank, a simple, poly-
ethylene "squeeze" bottle, with a suit-
able spout, is required.
STARTER BOX
For starting the engine.