X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from ms-smtp-01.southeast.rr.com ([24.25.9.100] verified) by logan.com (CommuniGate Pro SMTP 5.1.9) with ESMTP id 2080074 for flyrotary@lancaironline.net; Sat, 02 Jun 2007 07:37:25 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-103-061.carolina.res.rr.com [24.74.103.61]) by ms-smtp-01.southeast.rr.com (8.13.6/8.13.6) with SMTP id l52BaUUb025522 for ; Sat, 2 Jun 2007 07:36:31 -0400 (EDT) Message-ID: <001701c7a50a$4b46b6d0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Lynn's Tuning Summation was: [FlyRotary] Re: PP Ve??? was Re: Intake CFM air flow Date: Sat, 2 Jun 2007 07:36:42 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0014_01C7A4E8.C3ED8680" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0014_01C7A4E8.C3ED8680 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Great tuning summation! Lynn. While not a racer, my experience in experimenting with intake manifolds = on the rotary for aircraft use tracks with your comments. I initially = tried big, short tubes with my first intake and while it would have = probably given great HP at 8000+ rpm, the prop load prevented the engine = from ever getting to the magic land. When I went to smaller diameter = and longer tubes for the intake - performance at 6400 and below improved = considerably. About the only thing I might add a different perspective to is the rpm = regime for the HP tuning goal. Since I personally can't stand to see = the $$ flow at high cruise power settings , I seldom ever hit top HP in = flight for longer than a few minutes (just to see how it does). Most of the time I throttle back to 7.5-8.5 gph for economic cruise. = On the other hand, my personal priority is to accelerate rapidly on take = off and get a good initial climb rate to get my butt over and as high = above the trees as I can as quickly as I can. My (tongue in cheek) = viewpoint is that I don't care if you can hit 400 mph, if you don't = clear the trees, it doesn't matter {:>). So for my priorities, I concentrated on trying to achieve best power at = take off rpm - around 6000 rpm. The longer length and smaller diameter = tubes give the engine lots of oomph in that rpm regime. Clearly if you = wanted an all-out air racer you would more likely choose shorter bigger = tubes. =20 Thanks again for the great summation. Ed In a message dated 6/1/2007 8:20:04 P.M. Eastern Daylight Time, = daval@iprimus.com.au writes: Hi Lynn, since the Pport has a 'near lack of reversions' which are the source = of=20 "organ pipe" tuning theory; would you say that Pport engine is a lot = less sensitive to "tuned length" than a side port engine? Or does the Pport overlap between exhaust and inlet also cause a=20 pulsation which enhances 'organ pipe' tuned length. I think this is what I wanted to ask :) As you can in see in pictures of the Le mans engine, great care was = taken to have the correct length of inlet tract for each RPM. The engine = was not used even close to its maximum RPM or HP. And it had 700 HP. = Having poor performance in the tuned area is not no performance, and = they went to great lengths to get as much as was possible.=20 Larger diameter tubes gets a poor peak tuned effect but flows better = from less drag. A smaller diameter tube gives a more profound tuned = effect but flows less outside of the tuned RPM because of drag. And = they had big tubes. But the Pport flows like a turbine and power is = limited by the strength of the pieces. The multi piece crank may have = been the limiting factor. They could have made a few changes and had 800 = HP with good reliability. But they wanted perfect reliability. The = Lemans cars are forced to have broad power bands because there is a low = RPM 1st gear corner and a 230 MPH straight, so they went for the wider = power band that all competitors must have.=20 In a fixed length situation, you can only tune for one RPM, and that = must be for cruise and still have enough mid range to get the prop and = plane into the cruise speed range. Up on the cam, or on the pipe. It is = not impossible to have a killer motor that will not pull hard enough to = get a dyno reading without going up to RPM (Minimum used for racing) = with no load on the dyno, because the lightest load cannot be pulled by = the engine. It might even be that you cruise at or near peak torque and = never get to peak HP. The other choice would be to cruise just above = peak HP.=20 I gear the car to pass through peak power well before the end of the = longest straight. So we are above best power RPM for much of the = distance. The driver could not get around that one. Once the drag is = equal to the available power the car goes no faster in any case.=20 It is the first car to its top speed that beats you to the other end, = and seldom the car with the highest top speed. Notice that dragsters = that are going for a top speed records use a taller gear than the normal = get there first gear (lower). =20 The highest HP is not the answer unless there is a variable prop = system to keep the engine near its best power. Not fun if it takes = constant attention on clime out to keep things going the right = direction. The other end of the scale is a broad power band that allows = clime with no thought of engine RPM and on a fixed pitch prop.=20 It is possible to stall a prop with a bit of extra power while sitting = still or while the plane is moving slowly in a takeoff attempt. Most = people never get to feel that one because at lower RPM there is not = enough power being produced. But the prop blade stalls the same as a = wing stalls. Angle of attack is the answer. The speed of the air passing = through the prop disc alters the effective angle of attack, on any prop = fixed or adjustable pitch. Of course it is more likely on a high pitched = fixed pitch prop. It is also counterintuitive to pull off a bit of = throttle to stop the stall on a take off roll.=20 So the tuning is not for the max HP but a broad band of power, mostly = to the south or lower than the maximum HP. A bit lower HP at the bottom = of the range is fine, and helps avoid the slipping prop (like spinning = the wheels) and as the speed comes up and more power can be absorbed by = the prop the RPM brings on more power.=20 So, straight tubes over curved tubes. Worse if fuel is injected before = the curve or with a carb at the very end. Longer tubes give a broader = band than shorter tubes. Smaller diameter tubes give a better effect = over a smaller range. A peaky cam effect. Long tubes work better at = lower RPM. Short tubes work better at higher RPM. Probably a tapered = tube of medium length would be fantastic, but difficult to manufacture. = No inter connection of the inlet tracts is used on Pport engines.=20 A smaller higher velocity port gives a wider band than a huge slower = flowing port.=20 A bigger port moves the peak power up the RPM band and is peaky. A = smaller port works over a wider range, and is less sensitive to tuned = length. I had a factory Pport housing and it had small "D" shaped ports = with the flat part on the bottom. So it opened quickly and closed = slowly. Later aftermarket Pports (Modified factory) had huge rectangular = ports you could stick your hands in. Those made the power between 9,000 = and 10,700. =20 Lynn E. Hanover -------------------------------------------------------------------------= ----- See what's free at AOL.com. ------=_NextPart_000_0014_01C7A4E8.C3ED8680 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 Great tuning summation!  Lynn.
 
While not a racer, my experience in experimenting with intake = manifolds on=20 the rotary for aircraft use tracks with your comments.  I initially = tried=20 big, short tubes with my first intake and while it would have probably = given=20 great HP at 8000+ rpm, the prop load prevented the engine from ever = getting to=20 the magic land.  When I went to smaller diameter and longer tubes = for the=20 intake - performance at 6400 and below improved considerably.
 
About the only thing I might add a different perspective to is the = rpm=20 regime for the HP tuning goal.  Since I personally can't stand = to see=20 the $$ flow at high cruise power settings , I seldom ever hit top HP in = flight=20 for longer than a few minutes (just to see how it does).
 
  Most of the time I throttle back to 7.5-8.5 gph = for economic=20 cruise.  On the other hand, my personal priority is to accelerate = rapidly=20 on take off and get a good initial climb rate to get my butt over and as = high=20 above the trees as I can as quickly as I can.  My  (tongue in = cheek)=20 viewpoint is that I don't care if you can hit 400 mph, if you don't = clear the=20 trees, it doesn't matter {:>).
 
So for my priorities, I concentrated on trying to achieve best = power at=20 take off rpm - around 6000 rpm.  The longer length and smaller = diameter=20 tubes give the engine lots of oomph in that rpm regime.  Clearly if = you=20 wanted an all-out air racer you would more likely choose shorter bigger=20 tubes. 
 
 
Thanks again for the great summation.
 
Ed

In a message dated 6/1/2007 8:20:04 P.M. Eastern Daylight Time, = daval@iprimus.com.au = writes:
Hi=20 Lynn,
since the Pport has a 'near lack of reversions' which are = the=20 source of
"organ pipe" tuning theory; would you say that Pport = engine is=20 a lot
less sensitive to "tuned length" than a side port=20 engine?

Or does the Pport overlap between exhaust and inlet = also=20 cause a
pulsation which enhances 'organ pipe' tuned = length.

I=20 think this is what I wanted to ask :)
As you can in see in pictures of the Le mans engine, great care = was taken=20 to have the correct length of inlet tract for each RPM. The engine was = not=20 used even close to its maximum RPM or HP. And it had 700 HP.  = Having poor=20 performance in the tuned area is not  no performance, and they = went to=20 great lengths to get as much as was possible.
 
Larger diameter tubes gets a poor peak tuned effect but flows = better from=20 less drag. A smaller diameter tube gives a more profound tuned effect = but=20 flows less outside of the tuned RPM because of drag.  And they = had big=20 tubes. But the Pport flows like a turbine and power is limited by the = strength=20 of the pieces. The multi piece crank may have been the limiting = factor. They=20 could have made a few changes and had 800 HP with good reliability. = But they=20 wanted perfect reliability. The Lemans cars are forced to have = broad=20 power bands because there is a low RPM 1st gear corner and a 230 MPH = straight,=20 so they went for the wider power band that all competitors = must=20 have.
 
In a fixed length situation, you can only tune for one RPM, and = that must=20 be for cruise and still have enough mid range to get the prop and = plane into=20 the cruise speed range. Up on the cam, or on the pipe. It is not = impossible to=20 have a killer motor that will not pull hard enough to get a dyno = reading=20 without going up to RPM (Minimum used for racing) with no load on the = dyno,=20 because the lightest load cannot be pulled by the engine. It might = even be=20 that you cruise at or near peak torque and never get to peak HP. =  The=20 other choice would be to cruise just above peak HP.
 
I gear the car to pass through peak power well before the end of = the=20 longest straight.  So we are above best power RPM for much = of the=20 distance. The driver could not get around that one. Once the drag is = equal to=20 the available power the car goes no faster in any case.
 
It is the first car to its top speed that beats you to the other = end, and=20 seldom the car with the highest top speed. Notice that dragsters that = are=20 going for a top speed records use a taller gear than the normal get = there=20 first gear (lower).  
 
The highest HP is not the answer unless there is a variable prop = system=20 to keep the engine near its best power. Not fun if it takes constant = attention=20 on clime out to keep things going the right direction. The other end = of the=20 scale is a broad power band that allows clime with no thought of = engine RPM=20 and on a fixed pitch prop.
 
It is possible to stall a prop with a bit of extra power while = sitting=20 still or while the plane is moving slowly in a takeoff = attempt. Most=20 people never get to feel that one because at lower RPM there is not = enough=20 power being produced. But the prop blade stalls the same as a wing = stalls.=20 Angle of attack is the answer. The speed of the air passing through = the prop=20 disc alters the effective angle of attack, on any prop fixed or = adjustable=20 pitch. Of course it is more likely on a high pitched fixed pitch prop. = It is=20 also counterintuitive to pull off a bit of throttle to stop the stall = on a=20 take off roll. 
 
So the tuning is not for the max HP but a broad band of power, = mostly to=20 the south or lower than the maximum HP. A bit lower HP at the = bottom of=20 the range is fine, and helps avoid the slipping prop (like spinning = the=20 wheels) and as the speed comes up and more power can be absorbed by = the prop=20 the RPM brings on more power.
 
So, straight tubes over curved tubes. Worse if fuel is injected = before=20 the curve or with a carb at the very end. Longer tubes give a broader = band=20 than shorter tubes. Smaller diameter tubes give a better effect = over a=20 smaller range. A peaky cam effect. Long tubes work better at lower = RPM. Short=20 tubes work better at higher RPM. Probably a tapered tube of medium = length=20 would be fantastic, but difficult to manufacture. No inter connection = of the=20 inlet tracts is used on Pport engines.
A smaller higher velocity port gives a wider band than a huge = slower=20 flowing port.
 
A bigger port moves the peak power up the RPM band and is peaky. = A=20 smaller port works over a wider range, and is less sensitive to tuned = length.=20 I had a factory Pport housing and it had small "D" shaped ports with = the flat=20 part on the bottom. So it opened quickly and closed slowly. Later = aftermarket Pports (Modified factory) had huge rectangular ports you = could=20 stick your hands in. Those made the power between 9,000 and 10,700.=20  
 
Lynn E. Hanover
 



See what's free at AOL.com.=20
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