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I use a small manifold to smooth out the induction
pulses, before that the pulses would affect the pressure reading and probably
the computer also.
Rino
----- Original Message -----
Sent: Tuesday, November 02, 2010 12:03
PM
Subject: [FlyRotary] Re: EM2
Numbers
Ed,
I measure the manifold pressure at the unused oil injection ports in the
rotor housings. The EM-2 MAP reads in the upper 20's while at WOT, so I
don't think I have a problem with this. The MCT was as received, which
was set up for Tracy's injectors. I assume they were 460cc, but that's
just a guess. I'm running 60# DEKA IV injectors. Could there
possibly be an impedance mismatch between the two types?
Mark
On Tue, Nov 2, 2010 at 9:09 AM, Ed Anderson <eanderson@carolina.rr.com>
wrote:
Hi Mark,
Injectors are certainly large enough - six
injectors at 60 lb/hr would give you a max flow rate capacity of around 58
gallons/hour - far more than you are reporting fuel burn wise.
I guess what I am wondering is how your manifold
pressure is registering at WOT. The PP as I recall can have a problem
providing reliable/consistent manifold pressure - no good source? So
exactly how is your EC2/3 getting its manifold pressure signal ?
What comes to mind is that if there is a problem getting a good consistent
manifold pressure reading at WOT - could that possibly result in your
injectors injecting less than you would expect.
In other words, if manifold pressure was low relative
to what you would expect at WOT (near ambient) then turning up the manual
mixture control would only provide adjustment against the smaller target
pulse duration for that lower Manifold pressure rather than WOT manifold
pressure.
Ed
Sent: Tuesday, November 02, 2010 8:24 AM
Subject: [FlyRotary] Re: EM2 Numbers
Hi Mark
Are you in a position to confirm your fuel rail pressure?
Fuel injected = Pulse width AND injector size AND fuel pressure.
Cheers
Steve Izett
On 02/11/2010, at 4:42 AM, Mark Steitle wrote:
Tracy,
As I recall the low end numbers are around -50ish. So there is
still room for adjustment. When running WOT, turning the
mixture knob full CW doesn't get the mixture bar to show up on the EM-2
screen. I find this odd as I'm running 60# injectors. I guess
that's why the low end numbers are in the -50 range.
I'll post a question on the Lancair list regarding the most
efficient cruise speed for the Lancair ES airframe.
Mark
On Mon, Nov 1, 2010 at 3:03 PM, Tracy <tracy@rotaryaviation.com> wrote:
"So, if it is going LOP in those addresses, which
it is, it would explain why power drops off as I open the throttle
to WOT."
That's new data to me. Yes, that would
certainly cause a loss of power. Are you able to
compensate by turning up the mixture control? Are the MAP table
values at the low end above minimum value? The right thing to do
depends on these answers. If answer is yes to the 2nd one,
then you should bump up the value in Mode 3.
The most efficient
point on most airframes is the point where the induced drag curve
crosses the parasitic drag curve. On RV's that happens at around
an indicated airspeed of 135 mph. It will probably be higher than
that on a Lancair but I've never seen the curves on that airplane.
Tracy
On Mon, Nov 1, 2010 at 3:34 PM, Mark Steitle
<msteitle@gmail.com> wrote:
Tracy wrote:
Having said that, I think there is still a good possibility
that your drop in power above 6000 is not due to runner
length.
Tracy,
I suspect it could be tuning as I've hit the max
adjustment (+127) on the EC-2 MCT for the addresses in the upper
20" range, so it looks like I need to adjust the injector pulse width
and then start over on the tuning. So, if it is going LOP
in those addresses, which it is, it would explain why power drops
off as I open the throttle to WOT. I'll do more tuning when I
get my updated EC-2 back. (will go out in today's mail)
Where does one find the "most efficient operationg point" for a
particular airframe? Is this the same as LDmax?
Mark
On Mon, Nov 1, 2010 at 1:28 PM, Tracy <tracy@rotaryaviation.com> wrote:
"The lowest fuel burn per HP generated always occurs at the
torque peak as that is where the engine takes in the most amount of
air for each revolution of the engine. The VE is
optimum. In other words it is the most efficient operating
point for the engine."
Mark,
That
is the point of minimum pumping losses in the engine, NOT the most
overall efficient point of operation. It ignores
the many other factors that affect BSFC. If you look at
Mazda's data on BSFC, the best point is usually around 5000
rpm.
It also ignores the most efficient operating
point of your airframe. If you tune the engine for a higher
rpm torque peak you WILL make more HP, you will fly faster but
you will burn a lot more fuel.
Having said that, I think
there is still a good possibility that your drop in power above 6000
is not due to runner length.
Tracy
On Mon, Nov 1, 2010 at 11:54 AM, Mark Steitle
<msteitle@gmail.com> wrote:
Al,
Isn't the formula HP= (torque x rpm)/5252.
I'm more focused on peak Volumetric Efficiency (VE).
According to Fundamentals of Intake System Design,
(ACRE) "The lowest fuel burn per HP generated always occurs
at the torque peak as that is where the engine takes in the most
amount of air for each revolution of the engine. The VE is
optimum. In other words it is the most efficient operating
point for the engine."
So, I will be good tuning for peak torque. Do
you have a dyno chart on your 20B that you will share? I
find it interesting that your intake runners are only 13".
Mark
On Mon, Nov 1, 2010 at 11:10 AM, Al Gietzen
<ALVentures@cox.net> wrote:
Keep
in mind that the graph is peak torque (T)); not peak HP.
The peak HP (which is what you’re after would be at higher
rpm. HP = T x RPM
Al
-----Original
Message-----
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of stevei@carey.asn.au
Sent: Monday, November 01,
2010 1:09 AM
To: Rotary motors in
aircraft
Subject: [FlyRotary] Re:
EM2 Numbers
Hi Mark
I have
attached the Leman intake dimensions from Paul
L.
Hope this
is helpful. Can't remember whether this measurement was to the
rotor face or manifold face.
<image001.gif>
On
01/11/2010, at 8:40 AM, Mark Steitle
wrote:
I
understand the sausage illustration. But if what you
propose were true, then why did Mazda make such a
major effort to design and implement the variable intake on
their LeMans 26B p-port motor? That tells me
that runner length does make a significant difference
on the p-port motor. Also, if tuned runners didn't matter
for peripheral ports, then why do they tune the exhaust runners
on the 13B's? Somewhere I have a chart showing the effect
of runner length, but I'm not sure that the data is
from a p-port motor.
On Sun, Oct
31, 2010 at 7:27 PM, Bill Bradburry <bbradburry@bellsouth.net>
wrote:
Mark,
I don’t
think that will work with the PP. You never actually block
the inlet. You just cut off the end of the flow of air as
the apex flies by and it starts to fill the next chamber.
Think of the flow as a long sausage that is going through a
propeller made of a strand of wire 2 or 3 MM thick and being cut
into sections. It is never blocked. I doubt that
there are any reflections and if there are, they would be very
small and of little benefit to enhance.
I think
that is why the PP is so much stronger than the side
port.
Bill
B
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mark
Steitle
Sent:
Sunday, October 31, 2010 8:01 PM
To: Rotary motors in
aircraft
Subject: [FlyRotary] Re:
EM2 Numbers
Sorry for
the delayed reply, but I had to go to the hangar and measure the
runner length to be sure. It is 24" bellmouth to rotor
face, 2" OD. Exhaust is 2" OD also, running the stock 20b
exhaust splitters.
So, my
power seems to peak around 6000 rpm. What length intake
runner length would it take to bring peak power up to
around 6500 rpm?
On Sat, Oct
30, 2010 at 3:53 PM, George Lendich <lendich@aanet.com.au>
wrote:
That's interesting; can you tell me what is your PP size, runner
length and exhaust header ID size.
Sent: Saturday, October
30, 2010 7:38 PM
Subject: [FlyRotary] Re:
EM2 Numbers
Bill,
With the
current setup, it appears to be around 6000-6100, but I'm still
tuning on the upper addresses of the EC-2. My old engine
did best around 6500-6600 running the same prop. So, I
feel there is something that isn't quite right on the new P-Port
motor... maybe intake runners too short, intake or exhaust too
restrictive, timing off a bit, etc. It definitely makes
more hp than the old motor did in the 5000-6000 range, but I
feel that it should be producing more hp than I'm seeing in the
6000-7000 range.
So, things
are still developing. Yesterday, I reinstalled the old
air-filter box which has a ram-air feature incorporated into the
design. I haven't flown it yet to see if there is any
improvement, but I hope to see at least a little
improvement.
On a side
note, I have determined that there is a 250 rpm discrepancy
between the rpm readout of the EM-2 and that of the M/T prop
controller. I have an optical tach that I will be using to
determine which one is in error.
Stay tuned
(no pun intended),
On Fri, Oct
29, 2010 at 8:30 PM, Bill Bradburry <bbradburry@bellsouth.net>
wrote:
Mark,
It
would seem that if you flattened the pitch of the prop, the
engine rpms would increase, but at some point, you would begin
to lose airspeed and start to slow down because the prop was
just not taking a big enough bite. Conversely, it seems
that if you increased the prop pitch, the engine rpms would
decrease, but the airspeed would increase up to some point and
then after that, an increase in pitch would cause a decrease in
airspeed because you are taking too big a bite and the engine
just can not pull it. Somewhere in there is a “Sweet Spot”
of propeller rpm that gives the highest airspeed. Lets say
that this question assumes that you are at WOT and 8500 feet,
which should give you roughly a 75% power output. Do you
know where that sweet spot is with your
propeller?
Bill
B
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mark
Steitle
Sent: Thursday, October 28,
2010 10:00 PM
To: Rotary motors in
aircraft
Subject: [FlyRotary] EM2
Numbers
Rotarians,
Things have
been a bit quiet on the list lately, so I thought I would post
this picture of my EM-2 taken on a trip from Galveston, TX
(KGLS) to Lockhart, TX (50R) yesterday. I was level at
8500msl when taking the picture. A/C is a Lancair ES
(4-place), engine is a n/a p-ported 20b.
Please
disregard the oil temp as the reading on the EM-2 is measured
after the first cooler and before the second cooler. Oil
temp readings out of the second cooler (measured at the oil
filter pad) track water temps within a few
degrees.
Leaned to
"Economy Cruise" and dial the prop down to 1800 rpm and the
speed drops down about 15 mph and fuel burn drops to 9.1 gph.
You pay dearly for that 15 mph but sometimes it is just
too much fun to slow down.
Mark S.
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