Stephan's Sonex #1627 Builder's Log

116.40 hours
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The Jabiru 3300 is a 120HP purpose-built aircraft engine officially supported by Sonex.

This appears a solid engine overall and it often a choice by Sonex builders who want the additional power. However, I have reviewed a number of Sonex build logs and have come up with the following observations:


  • High CHT temperatures, even after break in
  • Requirement to frequenty re-torque the heads/bolts 
  • Front Cylinder head must be cut to fit cowling


The bottom line is that this engine runs hot, even when the recommended ducting provided by Sonex is installed. Temperatures are difficult to manage without an adjustment in flight (e.g. running richer or reducing power). Touch-and-gos and ground running on a hot day are generally not possible. 


The high CHT temperatures cause the aluminum to yield causing exhaust gases to blow by the head of the cylinder, further increasing the temperature inside the cowling. The blow by also causes a reduction in compression and therefore performance. 

Last Updated 2013/06/02 10:51:45PM