nuts & bolts
shop talk
Automatic Engine Dryer Project
New and improved since 2007
DAVID BARKER, EAA 587700
Since the first do-it-yourself engine dryer kit story appeared in the April 2007 issue of EAA Sport Aviation, several hundred EAA members have built
one for themselves. This simple unit is an inexpensive
way to help get your engine to its rated time between
overhauls. However, several limitations of the original
design have become apparent, particularly in humid parts
of the world. Some users have experienced short service
intervals because of the need to re-dry the silica gel. These
round trips to the kitchen oven can be a nuisance.
The following design automates the entire process,
featuring “plug in and forget” operation. The original
design has been updated to include electronic humidity
sensing of the moisture content in the silica gel. When
the moisture content reaches a preset threshold, the
engine air circulation pump is shut off. At this point, a
purge valve for the silica gel desiccant reservoir opens
to the ambient environment, and an internal heat lamp
turns on to warm the silica gel to about 200°F. This
drives the moisture out of the silica gel. Upon detecting
Automatic purge engine dryer and pump
