is currently>set to redline the prop (2700 RPM) at full power at my
normal cruise>altitude of ~5000 ft. In climb out at 90 mph, I can
achieve 1667 FPM at>~2300-2400 Prop RPM [4080 engine RPM] at my
normal flying weight. 1600 FPM>isn't too bad at 2100 lbs, but if I
had a variable pitch prop, I could>develop full power during climb
and get closer to 2000 FPM.>
I wasn't thinking what this "hand grenade sounded like running at
full>power" when you suggested looking at a higher PSRU ratio. All I
could see>was $$$$$. The engine is very smooth at full power and
emits a pleasant,>masculine supercharger whine.
The 3.8L SC engine is rated at 210 HP in the car. While I have
never had it>on a dyno, I have no doubt that I am achieving something
in that range or>better. I'm very pleased with the performance of
this engine, but I would>be even happier if it had a two speed
transmission.>
Before buying an in-flight adjustable prop, I will change the pitch
on the>Warp drive from 17 to ~12 degrees of pitch at the tips, then
record the>climb performance.
Keep up the good work on the NG. I'm learning a lot lurking in the
bushes.>
John Steere
Thanks for clarifying the numbers John.
Yes on your SC HP. I was referring to the normally aspirated V6
mentioned by Holger. I was not clear on that point. I am looking
forward to the data at 12 degrees of pitch on the Warp drive prop.
1600 FPM is 26.6 FPS straight up with 2100 pounds is 56,000 pound
foot per second or 101 net HP required for climb alone. This is net
HP out of the prop so giving the prop the benefit of the doubt at 80%
efficient that is 127 HP out of the engine. This is just the climb HP
required to lift that weight at that rate so the aerodynamic drag is
not included in this calculation however it is rather low at only 90
MPH.
Calculating the drag... giving things again the benefit of the doubt.
At a flat plate equivalent of three the drag would be 90^2 X .0026 X
3 or 63 pounds of drag. 90 MPH is 132 feet per second so 63 pounds of
drag times 132 FPS is about 8300 pound feet per second or about 15
net HP out of the prop. Out of the engine it is 15 HP dividing by .8
or 19 HP for a total of about 146 HP out of the engine. Probably a
bit more as induced drag from lift is a factor at 90 MPH. 90 MPH is
usually a bit below the bottom of the drag bucket MPH.
I still think you need to get the RPM up to at least 4500 on the
engine somehow. I think you would still be better off cutting down
the diameter of the prop.
What is your top speed so far John?
Paul Lamar