Gordon Grant wrote:
The Airmaster is an electric constant speed unit that can also be used manually in flight. Mine is set for 5600RPM for Take Off and Climb and 5200RPM for Cruise. I usually leave it at that, but have found that setting it manually to 4800RPM at 27inches MFP gives sligtly better cooling.
The engine has done 474 hours and has always been run on the Rotax recommended oils (can't remember the exact make but it was the Shell motorcycle oil pror to switching to the Aeroshell Sport Plus). Oil and filter are changed every 6 months or 50 hours and I only use ethanol-free Mogas. The oil tank had no sludge when I cleaned it out.
I forgot to mention that I had already swapped the wires betwen the two temp senders and the high readings moved with the swap. I replaced the oil pipes in case they were collapsing/blocked internally and had my work checked and signed off by an LAA Inspector who said the pipes were routed correctly.
The oil pressure is 4.5 Bar at start and drops to 2.5 at 'normal' temps and then to 2.2 when temp rises to 130C. These figures are slightly lower than previous years - is it at all possible there may be aproblem with the oil pump? I will try flushing the oil cooler.
Hi GG,
I have a brand new Sonex/912ULS/Airmaster CS, in the erly stages of test flying.
I have had cooling issues in general & oil cooling in particular, from the start.
"Fixes "? to date;
Improved air exit by adding a pilot operated electric cowl flap - some effect
Enlarged the air entry directly in front of, largest size, oil cooler that Rotax supply - some effect
Installed anti hose collapse spring on the outside of the oil cooler to pump hose - the only hose with a tight bend - no difference
Created a separate air circuit for oil cooler - big impact
My oil temperatures are now similar to yours - I can usually manage the situation and keep the oil temp at about 110C in cruise. Much depends on OAT (30C @ 4500ft the other day - had to return to airfield, oil cooled rapidly on decent).
I am still not happy with the temps - I live in NSW Australia - it is important to me that my Sonex will be able to operate comfortably (the engine) in 30-40C ambient. The goal is to have Cruise Oil 90-100C & Coolant 90-95C To acheive this will be completely redesigning my cooling system lay out and altering my cowling to suit.
Your Airmaster setting are quite a bit diffrent from mine - at WOT:
TO 5700rpm
Climb 5400 rpm
Cruise 5300 rpm
I have experimented with the manual override and found that reducing power and adjusting to 5200 rpm in cruise usually reduces my oil temperature slowly.
All my oil hoses are covered in fire resistance sleeves, making judgements about hot collapse difficult - I am contemplating removing most/all of the fire sleeves, to better asses the condition of the hot hoses.
