Joe, I have stored my Wren MW 54 indoors, and out in my model shed (non heated in the winter but very dry) with much success. I now have three engines I store the same way.

Here is a letter I received from Mike Murphy of Wren Turbines on how to store the engines for the winter. I hope its OK to post it.. I edited things not pertaining to the storage question I had asked...


"Hello Andrew, Mike Murphy here.

The main issue about storage is of course moisture and this will affect the bearings. Jet A1 and
paraffin both have a fair quantity of water absorbed from the atmosphere and
therefore we need to get this away from the bearings when going into
storage. I would recommend running neat lube oil into the lubrication line
and spin the rotor gently by hand, to ensure it gets well into each bearing
and this will help displace any remaining fuel. Do not take the engine apart
to do this or you will spoil your balance and positioning of the bearings.
Keep the engine stored in a clean dry place and wrapped in your favourite
oily rag! A wipe of grease will ensure no rusting occurs on the case rear.

When next flying season comes around, wash the neat oil out of the bearings
using pressurized fuel into the lube line connection. Hold the engine
vertically, compressor upwards to ensure the fuel runs clean out and spin
the rotor quickly to help clear the excess. When you come to do your first
start, keep the fuel shut off and spin the engine well up on the starter so
if there is a fuel residue it will blow clear. Do one attempt at starting
with the fuel still off to allow any last residue to burn off cleanly with
the gas. After this you should be able to start up as normal with the
bearings lovely and free-running.


Regards

Mike. "