| Bill,
There are a number of silicone connectors in my intake, but the problem with this is that the runner length needs to be shorter and all of the pieces are butted together now. So, there is nowhere to shorten it without cutting tubing somewhere.
As Tracy suggested, I will hold off until I do some more tuning as it is likely that at least some of the problem is the mixture is going lean above 6000 rpm. The more I think about it, the more I think he hit the nail on the head. I'll do some tuning this weekend and see what improvement that gives.
Mark On Mon, Nov 1, 2010 at 7:22 PM, Bill Bradburry <bbradburry@bellsouth.net> wrote:
Mark,
Can you cut it and place a hose over the cut
so you can adjust the length till you get it figured out?
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Mark Steitle
Sent: Monday, November 01, 2010
11:02 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: EM2
Numbers
Agree, but I will proceed carefully else I fall into the "cut
it off twice and it is still too short" quandry.
On Mon, Nov 1, 2010 at 8:58 AM, <stevei@carey.asn.au>
wrote:
Hi Mark
The two inches would be backed up by the 26B data.
2" in the 5500 - 6500 rev range made approx. 1000RPM difference to
the peek torque curve.
On 01/11/2010, at 8:13 PM, Mark Steitle wrote:
I saw that one, but it is a bit illusive as to the actual runner
lengths. I think it is referring to the LeMans 26B setup
with variable intakes. It had a section of fixed length, then a
slide section. Depending on where the slide was set, it had a specific
overall length. I think this chart just shows what the slide section is
set at. Not really helpful to us if we don't know the length of the fixed
section.
I found another article titled Fundamentals
of Intake Design on PL's site that shows basically
the same information, but references total runner length. Based on that
chart, it appears that 21.8" would give me peak power around
6200-6500. My current runner length is 24" which by
extrapolation would put the peak power down around 5500 rpm, which is
where it is now. Looks like I need to shorten my intake
runners by 2".
On Mon, Nov 1, 2010 at 4:09 AM, <stevei@carey.asn.au> wrote:
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.
<Lemans-torque-curves3.jpg>
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.
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?
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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