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http://www.ultralightnews.ca/ Page 16 of 39
The Ultralight Store - your one stop ultralight store.
Once you have verified a spark plug colour and seen where your gauge reads with the proper colour then it is
now more important to watch for a CHANGE in the gauge reading from this "normal reading."
It is important to set your engine up for proper fuel to air mixture, your EGT gauge and probes can aid in
doing this. A lean mixture will run hotter on the EGT. A rich mixture will run cooler on the EGT but will
make increasingly less power. Ideally the highest EGT temps should come in at settings usually 5200 to 5800
rpm.
Reason for EGT temperature changes include:
Air intake leak.
Air fuel mixture too lean
Air fuel mixture too rich
Changes in density altitude
Changes in relative humidity
Changes in air temperature
Pre-ignition or detonation
Fault spark plug or ignition system
Improper prop load
Poor quality or grade of fuel
Improper fuel air ratio, plugged main jet, failed needle jet, or clip
3.3Fuel Pressure
As mentioned previously, it is recommended to maintain a constant fuel pressure under all conditions.
Additional monitoring of fuel pressure by means of a fuel pressure gauge may also be considered. One such
suitable gauge is manufactured by Westach and is available for pressure of 16psi and 80psi.
Figure 3.3.1 Westach fuel pressure gauge 029.20/029.21
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