OK see here for an explanation of my non-standard engine selection.

The bottom line is that I am getting a BIGGER, HEAVIER, MORE-EFFICIENTengine.

With airplane jet engines, you can get them SMALL and INNEFICIENT (F-18 Hornet) or BIG and EFFICIENT (Boeing 787).

This is because if you have more, bigger, compressor stages, you will get better efficiency... but at the cost of a higher weight, of course.

For this airplane, we will be using the PT6A-42, which is a bigger, heavier, stronger, more-efficient engine than the PT6-135 that the standard kit calls for.

This engine will offer more power than the standard -135 if run hard, and also offer more efficiency (lower fuel-flow!) if operated at a power output equal to the power output of the -135! This is accomplished with the dual-stage compressor of the -42, as opposed to the single-stage compressor of the -135.

Now, we DO have the issue of weight-gain... but weight! I mean wait! We can also get an ultra light-weight composite prop from Germany that is much lighter than the metal prop that comes standard on this plane from Hartzell. So, the light-weight prop will offset much of the weight gain from the second compressor! The result is a similar weight, but with a lot more power, available to a much higher altitude, and perhaps a little less fuel flow as well, if we operate at the same SPEED as a -135 airplane.

OK here are the tables I researched, showing the speed and fuel flow and 'goodness' for each engine, where 'goodness' is speed * range / fuel:

135, fl-240:

292 hp, 27.2 gph. hp per gph = 10.7. 265 kt 974 nm with 100 gallons to burn in cruise, if goodness is speed * range / fuel, then goodness=2581
334 hp, 30.3 gph. hp per gph = 11.0. 280 kt 924 nm with 100 gallons to burn in cruise, if goodness is speed * range / fuel, then goodness=2587
375 hp, 33.4 gph. hp per gph = 11.2. 291 kt 871 nm with 100 gallons to burn in cruise, if goodness is speed * range / fuel, then goodness=2535
435 hp, 38.8 gph. hp per gph = 11.2. 305 kt 786 nm with 100 gallons to burn in cruise, if goodness is speed * range / fuel, then goodness=2397
451 hp, 39.3 gph. hp per gph = 11.5. 309 kt 786 nm with 100 gallons to burn in cruise, if goodness is speed * range / fuel, then goodness=2429


-42, fl-240:

335 hp, 30.0 gph. hp per gph = 11.2. 280 kt 933 nm with 100 gallons to burn in cruise, if goodness is speed * range / fuel, then goodness=2612
453 hp, 37.0 gph. hp per gph = 12.2. 310 kt 838 nm with 100 gallons to burn in cruise, if goodness is speed * range / fuel, then goodness=2597
564 hp, 45.6 gph. hp per gph = 12.4. 333 kt 730 nm with 100 gallons to burn in cruise, if goodness is speed * range / fuel, then goodness=2430
578 hp, 47.5 gph. hp per gph = 12.2. 336 kt 707 nm with 100 gallons to burn in cruise, if goodness is speed * range / fuel, then goodness=2375

As you can see, at 452 hp, the bigger engine actually burns a bit LESS fuel (!) thanks, apparently, to the extra compressor.

And, if you push the bigger engine to it's limit at 24,000 ft, you just may see 336 kt, which is 386 mph.

Now, let me say right now, I don't think my balls are not big enough to go that fast.

BUT, I will save some fuel running at the SAME speed as the smaller engine, and I MAY decide to use some of that power reserve to go faster, at some point, if desired.