| David,
Mark S. (Colorado) had problems getting a good steady MAP signal with his slide throttle p-port engine. He ended up using the oil injection ports for MAP. Worked out well for him, so I copied his approach. The slide throttle is very close to the housing, so there is just a couple of inches of runner between it and the rotor port.
Mark S. (Austin) On Tue, Nov 2, 2010 at 6:39 PM, <hoursaway1@comcast.net> wrote:
Ed, Mark, manifold absolute pressure should be measured from the intake manifold as close to throttle plate as possible, this is your controlling authority for MAP & we all know with the rotary eng. strong pulses are generated & the t-body is where they are dampened the most, you can check this with a cheap vac. gauge connected near housing & near t-body & monitor the needle at the diff. positions, shaking violently near housing, shimmering slightly at t-body. David R. Cook RV6A Rotary.
----- Original Message ----- From: "Mark Steitle" < msteitle@gmail.com> To: "Rotary motors in aircraft" < flyrotary@lancaironline.net>
Sent: Tuesday, November 2, 2010 11:03:12 AM 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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