"Steere, John" wrote:
As I recall it was the Ford Thunderbird SC 3.9L V6 engine with the
supercharger. Dyno readings can sometimes be misleading depending on
who is running it. Was that the HP number Dave Blanton was claiming
or was that done on an independent shop dyno. There was a lot of
controversy about that as Blanton did not use the same measure of HP
as the rest of the world did (and still does).
My 1994 Mercury (Ford) Cougar over head cam 4.9L V8 is only rated at
200 HP. My guess is a stock Ford push rod 3.9L V6 is about 160 HP.
Here are a couple of pictures of the engine. Firewall forward weight
is over 500 pounds.
Paul Lamar
Paul;
The pictured engine is in my BD-4. Our discussion at Oshkosh sprang
>from my wish that I had an in-flight adjustable pitch prop. My
pitch 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
Having owned & flown a Lyc 180hp/cs prop 'stock wing' BD-4, I can tell
you that his climb rate is much better than I would have expected
hauling that kind of weight if he has the stock wings (not longer
span). I flew mine to OSH a couple of years ago with a neighbor in his
C-182. He was at gross weight & I was at my gross of around 1900 lbs.
We would break ground at around the same spot, I could rather easily
outclimb him and pass him on climbout (100mph vs 120mph climb speed. I
could outrun him below about 6k feet & he could outrun me up higher.
Neither of us had wheel pants & our cruise was around 150-155 statute
mph. I don't think I saw more than 1300 fpm when fully loaded. If John
is doing 1600 fpm at 2100 lbs with a fp prop pitched for cruise, he's
beating a 180 Lyc. My plane was rather dirty, but at 100mph climb
speeds that wouldn't make a lot of difference.
Charlie England
What are the two spans? What is the cord?
Paul Lamar
Paul;
My span is ~29 ft, a 22 inch extension on each side. The BD-4 chord is 48".
John Steere
Wing area is 116 square feet
Dynamic pressure at 90 MPH is 21 psf
Lift is 2100 pounds at 90 MPH.
Lift coefficient is 1.16 at 2100 pounds.
Lift coef. squared Cl^2 is 1.35
Wing aspect ratio is 7.25
Drag coefficient due to lift is 1.35 / (7.25 X 3.1415)
or 1.35/23 or .059
Drag due to lift alone is 143 pounds.
Net HP 143 times 132 feet per second or 18,876/550 or 34 net HP.
Engine HP is 42.5 with assumed prop eff. of 80%.
Total HP is now up to 146 + 42 or 188 HP at 4000 RPM.
Check my numbers. Always :)
These numbers are based on the reported climb rate. Lets check top speed.
Induced drag due to lift fades into the background as the Cl (the lift
coeff.) goes way down and we can go strictly on flat plate equivalent.
186 MPH is 272 FPS
Dynamic pressure at 186 MPH is 90 PSF
Flat plate equivalent area drag number is assumed to be 3
Drag is 270 at 186 MPH.
Pound feet per second is 270 X 272 FPS or 73,400
One HP is 550 pound feet per second.
Net HP out of the prop is 73,400/550 133 net.
Prop eff. is assumed to be 80%.
Engine HP is 166 HP
Check my numbers. Always :)
Looks like I underestimated the equivalent flat plate area. Probably closer to 3.4.
That error will hardly affect the HP required to climb however.
Lots of HP there John at only 4000 RPM with your super charged engine.
The Warp Drive prop is working pretty good too. You should bring it to
Sun & Fun next year and enter it in the Sun 100 race.
BTW did you modify that outlet duct on the intercooler?
Charlie, what was the top speed of your Lyc 180 HP BD4?
Paul Lamar
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