Bobby,
When you say “drive losses”
are you referring to the energy to turn the supercharger? Or are you
referring to the PSRU? If it is the SC, I wonder if anyone knows what it
costs in HP to run the PSRU?
Bill
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bobby J. Hughes
Sent: Tuesday, May 15, 2012 7:38
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Fuel Flow
Bill,
After a closer
review of the Eaton MP90 performance charts I believe my actual super charger
losses are less than I originally thought. 5000 crank rpm is about 8000 rpm for
the super charger.
5000 rpm / 30”
MP at 8000 ft. 150 HP – 10 for temperature rise and 10 for
drive loss nets 130 hp. That’s a BSFC of .40 at 8.6 gph. At 9.1 gph
it would be .43 BSFC. I suspect my fuel flow may be off by .5 gph.
At 6800 engine /
30” MP at 8000ft. Base HP of 215 – 12 for temp rise and 23
for drive losses nets 180 HP. A BSFC of .5 would be 15 gph and .53 would be
15.9 gph. Very close to the 16 gph I see in this configuration.
Bobby
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bobby J. Hughes
Sent: Tuesday, May 15, 2012 1:47
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Fuel Flow
Bill,
Without an
intercooler I don’t operate in the low rpm / high MP setup. I’m MP
limited to about 32” for cruise depending on altitude. I
don’t lean the mixture below 14.3-14.5 in the 32-34” range. I
do run 38-40” for takeoff and initial climb. F/A at 12.5-12.0 with water
injection for extra margin. Takeoff roll at 2450 rpm and then reduced to
2100-2200 for climb. MP drops some with the lower climb rpm but my water
injection stays on above 33”. My peak HP is with F/A around
13.5-13.7.
At 5000 rpm /
30” MP at 8000 ft I estimate a loss of 12HP for air temperature rise and
23 HP for drive losses. With a base HP of 150 -35 = 115 net HP. That
would be 8.6 gph at a BSFC of .45. Is the 23 HP drive loss costing me 2
gph? An IO540 should see a maximum 197 HP at this altitude / 118 HP at 60%
power.
I’ve managed
to shave a little weight off but I’m still around 1590- 1600
pounds.
Bobby
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]
On Behalf Of Bill Bradburry
Sent: Tuesday, May 15, 2012 10:32
AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Fuel Flow
Bobby,
The Renesis has a 10:1 compression
ratio. Are you sure you are not getting detonation at high (30-40)
manifold pressures and low (1700 prop) rpms? These considerations and the
fact that I just don’t have room to squeeze it in are the reasons that I
decided against a turbo. The stock (car) engine has a knock sensor, but
we don’t have any way to monitor it and with the noise and headsets to
cancel it out, I doubt that we would ever hear detonation unless engine parts
were flying past our ears. :>)
I would like a little more power, but for
me, it would be easier to install a 20B than to switch to a turbo. I have
enough room behind the engine that a 20B would set on my existing motor
mount. All I would have to do is make up a mount plate for the 20B that
has the mounting ears in the positions of the 13B ears. I could even use
a little more weight in the front for W&B, so the extra weight would also
probably work well also. My plane is heavier than a RV6/7 by about 500 lbs, so
I could use the HP on takeoff and same for cruise as well.
I briefly touched on this mount plate idea
a year or so ago with the Cozy Girrls, but they didn’t seem to be
interested in making the mount plate although it would be pretty simple to
leave 13B as well as 20B ears on a 20B mount.
The rotary HP is really a factor of the
rpm. When you dial it down in rpm, the HP drops to that level. I am
not certain what effect the turbo would have on this number, but for NA engine,
5K rpm is about 160 HP, 6K=180, 7K=200, etc.
This is pretty close to the same on all
the Dyno graphs that I have seen. Pretty much no matter how “souped
up” the engine is, it still follows that same HP curve. This
becomes a problem for those of us who want to develop 200HP but run at 5K
rpm. That aint gonna happen with the two rotor engine. :>(
Bill
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On Behalf Of Bobby
J. Hughes
Sent: Tuesday, May 15, 2012 10:02
AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Fuel Flow
Charlie,
This configuration
is my sweet spot. Efficiency declines rapidly with faster rpm. I can also
run the same prop rpm at a lower manifold pressure 24-26 “and see almost
the same fuel burn at 150 mph TAS. Increasing the manifold pressure to 30 or a
little higher increases speed but the fuel burn barely increases. At the other
extreme with prop set to 2350-2400, 30 -32” MP I see a top speed of 190
mph but the fuel burn shows 16 gph. Not good. The lyc RV10’s are way more
efficient at this speed. I suspect the super charger drive losses are a big
factor at the high power settings. Possibly up to 2 gph?
It’s possible the fuel flow is not accurate in the high power
configuration. I’m not comfortable running the engine that hard for
very long so calibration verification is not possible. I’ve been
reconsidering a turbo but still not convinced the renesis exhaust ports are up
to the abuse. Although a looser turbo may eliminate the housing damage that has
occurred in the turbo RX8’s. I wonder what intercooled,
38” MP at 1900 rpm would do for speed and fuel burn?
Bobby
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On Behalf Of Charlie
England
Sent: Monday, May 14, 2012 8:57 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Thanks Tracy!
Hi Bobby,
Those are pretty good numbers for a 4seat plane, even a -10, at that fuel flow.
Have you checked it at around 11gph?
Thanks,
Charlie
On 05/14/2012 03:26 PM, Bobby J. Hughes wrote:
Cruise rpm is
typically 1700-1825 prop \ 4850-5200 engine. The low rpm may influence my
EGT’s. In this configuration I see 160-165 MPH TAS at 8-8.5 gph at 6000
foot. It does a little better up high.
Bobby
RV10
Bill,
I see around 1650F
max. At cruise altitude running less than 30”MP I can lean to about
1475F.
Bobby
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Bradburry
Sent: Saturday, May 12, 2012 7:06
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Thanks Tracy!
The EM-2 mixture is working fine now, Tracy. I appreciate
the rapid turnaround.
I wanted to ask you about the EGTs I
should expect from the Renesis. I am getting EGTs in the upper 17s.
I think I expected them to be a couple of hundred lower than that. I
don’t doubt the accuracy because the EGTs report a pretty accurate OAT
when I first arrive at the hangar and before I start the engine.
I did some relearning of the EC-2 during
the flight today between 18 and 29 inches manifold pressure. This was
done at 2K feet. The MAP was lowered considerably and now the mid point
of the graph is pretty close to the knob center, maybe 12:30-1:00
o’clock.
A good explanation of how to lean would be
very helpful for me at this point. Also I am wondering what fuel burn
most are getting at cruise. I am still calibrating this function, but I
would like to know what to expect if I ever get it right.
Bill B