tffy a écrit :
This is for a hypothetical ultralight design, so just looking for
suggestions here of where to look at... hopefully a 4-stroke, purchase
price doesn't matter much, certification status doesn't matter either.
Long time before overhaul matters A LOT... so, the longer the better.
Is there anything out there in the 80-hp range? How about a motorcycle
engine conversion - how long can those go before needing to be
overhauled?

Thanks!


Hi,

In the 80 hp 4-stroke range, you'll find only the Jabiru 2200 and the
Rotax 912. Only those engines do have demonstrated in-flight reliability
and substantial TBOs.
Others engines CAN be installed, but be prepared to spend LOTS of time
sorting out cooling and installation problems.
It takes many test-cell and flight-test hours to make a reliable engine
out of a prototype.
And many many engine overhauls to ensure an acceptable TBO.
Besides, most road vehicle or boat engines are heavy. Remembers road
engines are designed to run at relatively low engine power settings,
with the occasional short burst at full power.

On the other hand, aero engines spend their operational life running at
60-75 % power.

My two cents,
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr