> > Then they wonder why the engine is not generating the
claimed for
HP.
> >
> > I explained this to some guy on the OSH line with a Ford V6
complaining
> about
> > lack of power with a 1.7 psru. I suggested a higher ratio
and he
got this
> > pained expression on his face. He was thinking what his hand
grenade
> sounded
> > like running at full power (full prop load) at 4000 RPM.
Holger Stephan wrote:
The Javelin conversion Ford V6 I bought a while ago was dyno'ed to
put out around 180HP at 4300 RPM. If that is not enough I'd say the
guy got himself the wrong engine.
Holger
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
Paul;
The last time I checked the top was ~186 MPH. I agree with 4500 engine RPM
as a target. That is the peak of the HP curve recorded on another SC in a
four wheel vehicle.
John
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