- Aug 8, 2009
No real reason for the 32:1 reference just a common mix ratio that is less fuel / more oil than the otherwise standard manufacturers specification. I was not sure if you had referenced 40:1 or 50:1.Nice to hear! My rough calculation for 20% less fuel would mean 40:1 for the same amount of oil per engine cycle. Out of curiosity, why do you say 32:1?
It would be much better to have an oil injection system so a fuel lean would not also lean the oil.
The limiting factors for two cycle operation are excessive temperatures and inadequate lubrication.
The lubrication issue is best addressed with the oil injection system.
The temperature issue comes from several variables. That is throttle position/manifold pressure, fuel air ratio, and RPM.
You have commented on the first issue and are attempting to counter with the second issue. It is possible to balance these two issues within narrow limits.
The application given has limited ability to control RPM as the load is a fixed pitch propeller. Heat rejection is directly tied to RPM if other variables are constant. If a variable prop could lug the engine to 1/2 the rpm (and half the power) the LOP option would likely work well. Set up for max power at takeoff and at altitude is probably not a good idea without an extensive test program.
I have many hours with a Rotax 582 or Hirth and electric IVO Prop. I prefer to take off WOT and leave the throttle open while bringing the rpm down with the prop pitch. If that were done to 10,000 feet I am certain the mixture lean would be worth while if oil injection were installed.
If power is reduced with throttle or rpm EGTs and CHT can be somewhat increased (safely) by a mixture lean.