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http://www.ultralightnews.ca/ Page 14 of 36
The Ultralight News - your one stop Ultralight News.
The equipment listed in Table 3-1 can be purchased from AATI Pty Ltd.
Table 3-1
Description Part No.
Westach Exhaust gas temperature measuring device (2x, as a set) 029.30
Westach Cylinder head temperature measuring device (2x,as a set) sparkplug 14 mm 029.31
Westach Cylinder head temperature measuring device(2x, complete) sparkplug 10 mm 029.32
Westach Fuel pressure measuring device 029.20
Westach Tachometer 029.14
2.7Cylinder head temperature
To allow for expansion of the piston in an air cooled engine, the tolerance between the piston and the
cylinder wall is essential for expansion and contraction. As the piston and cylinder heat under normal
operating conditions they expand, the piston becomes "larger" while at the same time the cylinder walls
expands. Engine manufactures allow for this "expansion" and "contraction" when they produce the engine.
Normally a Hirth air cooled engine should read between 350F to 410F on a cylinder head temperature gauge
(CHT). When an engine overheats the amount of expansion between these parts is greater than allowed - the
piston becomes too tight in the cylinder and the piston "seizes' creating permanent damage to the piston and
or cylinder wall
Figure 3.1.1 Dual Westach CHT 029.31/029.32
AWestach CHT (Figure 3.1) gauge uses a Type K thermocouple, which requires no power. The
thermocouple produces a small voltage which to work properly requires good continuity to reach the
instrument
The thermocouple, which is available in two different sizes depending on the spark plug used - is mounted
under the spark plug, and replaces the spark plug washer.All of the Hirth two cylinderengines use a
10mm or a 14mm probe.
CHT temperatures in excess of 280°C or 536°F are a result of :
Lack of oil in fuel or NO oil in the fuel.
Poor piston cylinder lubrication, due to poor quality of oil.
The use of a fan belt other than that supplied by Hirth, a loose, or damaged fan belt.
Ablocked fan intake duct, or blocked cylinder head fins. (Insect nesting, mice etc.).
Insufficient cooling due to air intake design.
Pre-ignition or detonation, caused by old fuel, improper octane, ignition timing.
2.8Exhaust gas temperature
Agauge that we recommend on all Hirth two stroke engines is the Westach Exhaust Gas Temperature gauge
(EGT) as in figure 3.2.1. This gauge is a reliable measurement tool that measures the exhaust gases as they
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