X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.123] verified) by logan.com (CommuniGate Pro SMTP 5.3.3) with ESMTP id 4155086 for flyrotary@lancaironline.net; Sat, 06 Mar 2010 23:19:03 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.123; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.0 c=1 a=nO8yt6oiackA:10 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=QdXCYpuVAAAA:8 a=7g1VtSJxAAAA:8 a=ekHE3smAAAAA:20 a=UretUmmEAAAA:8 a=Ia-xEzejAAAA:8 a=kviXuzpPAAAA:8 a=nUuTZ29dAAAA:8 a=Uk3mjJlrXhuVcEzzEpYA:9 a=vkFOEpex3uCL1y7J_X8A:7 a=q1l6OgRTd1GvTFZ62p_fGZbf1R0A:4 a=wPNLvfGTeEIA:10 a=1vhyWl4Y8LcA:10 a=EzXvWhQp4_cA:10 a=iVkDmfvjeKcA:10 a=4vB-4DCPJfMA:10 a=nucvw1h3S1bt4iRp:21 a=DVIZ4QUfmzEujlrD:21 a=SSmOFEACAAAA:8 a=Fh761I7YvXf2AW3ClPUA:9 a=CYJACpUo4eywcYGfXsMA:7 a=6MEFoHxcBW1gV59peZPO6CiFODgA:4 a=yqwDrFoCYa3GODcT:21 a=aL1aTE52LenD4Yb5:21 X-Cloudmark-Score: 0 X-Originating-IP: 75.191.186.236 Received: from [75.191.186.236] ([75.191.186.236:3176] helo=computername) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id EF/A9-23425-319239B4; Sun, 07 Mar 2010 04:18:28 +0000 From: "Ed Anderson" Message-ID: To: "'Rotary motors in aircraft'" Subject: Performance 68x72 prop. [FlyRotary] Re: TB size, Travel and Power Date: Sat, 6 Mar 2010 23:18:37 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0003_01CABD83.598B7E80" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 Thread-Index: Acq9pDG53cMURCszSoqLELgcmlzOwAACKXmA In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_0003_01CABD83.598B7E80 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Actually, Mike, I do have a 68x72 Performance prop that I used for my = 2.17 gear box. Don=92t know if that=92s sufficiently different from yours to = make a difference or not. Let me know if interested =96 for the paltry sum of shipping costs, just might be able to get it to you {:>). Don=92t know = if the blade profile will fit your spinner cut our or not =96 that=92s about = the only problem I could see. =20 Ed =20 Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm =20 _____ =20 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills Sent: Saturday, March 06, 2010 10:13 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: TB size, Travel and Power =20 Tracy, =20 Yes I have confirmed that I get full ambient pressure at 2/3 (roughly) throttle near sea level. And yes I still have the POS vacuum gauge. I = know it needs replaced - just havent had the opportunity yet. =20 My point in bringing this up yet again was to emphasize the point Ed = made a couple of posts back - that this whole thing is a complex problem with a = lot of variables. And to not dive in and start whacking on the prop until certain that is where the problem is. In my case I'm not sure it is. = Full ambient MP at the TB doesn=92t indicate how well the intake is flowing = and it is entirely possible to have full MP but a very poor performing = manifold. Guys in racing make lots of $ porting and flow testing manifolds. =20 I need to make some changes to the intake anyway for other reasons so = I'm going to focus on that first. And once that's done, if I'm still giving = up some RPMs then I'll take a look at the prop. Unless of course I can do = it the easy way as Al suggested and borrow a prop. On that note, are there = any of you RV guys that have upgraded from the 2.17 gear ratio to the 2.85 = that have a "wrong way" prop you'd be willing to lend for a test? =20 Meanwhile I havent been able to fly for the past 3 weeks due to this = crappy weather. Why's it always have to rain on the weekends? Its not supposed = to rain in SoCal at all. =20 Mike Wills =20 From: Tracy Crook=20 Sent: Saturday, March 06, 2010 7:06 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: TB size, Travel and Power =20 Mike, you are measuring the MP exactly where you should, You can't do it properly anywhere else, at least not with a simple instrument. =20 But are you at last confirming that you DO have full ambient MP at 2/3 throttle setting? That IS an important question if you want to know = the right answer to your question. BTW, ditch the vacuum gauge (if that's what you are using) and get a proper MP gauge. =20 Tracy On Fri, Mar 5, 2010 at 9:30 PM, Mike Wills wrote: Ed, =20 I hear what your saying (and I get it). Here's the thing, and I admit I = may have a misunderstanding here. Your explanation applies if you are = measuring manifold pressure essentially at the rotor face. If you measure MP = closer to the TB as I do unfortunately, it is possible to see ambient at full = throttle but have restrictions in the intake tract that would result in less than ambient at the rotor face. Conversely (and again theory - I'm open to = being shown wrong here), a properly designed DIE manifold would show ambient = MP measured at the TB and greater than ambient measured at the rotor face. =20 I accept that by trimming the prop I can lighten the load and gain some = HP (though some here seem to think that HP will increase linearly with RPM = to infinity and I don=92t buy that either). But as you alluded to in your previous, there's some potential for mistake in trimming any prop until = you are quite sure that you are not HP limited by something other than load. = And I'm not sure yet. Just a feeling based on the fact that I'm using a cut = down RX-7 TB that=92s maxed out about 1/3 short of fully open. And honestly I = still havent dug any deeper because the airplane is flying well and has good performance. But sooner or later I'm going to want to get more than the 5700RPM I'm currently getting - I want all the performance that=92s = there. =20 Mike Wills =20 From: Ed Anderson=20 Sent: Friday, March 05, 2010 6:36 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] TB size, Travel and Power =20 I am apparently not doing a very good job making the point about the relationship between throttle body size, throttle travel and engine = power clear. So here is another try at it - using extreme examples and no = math. Let=92s assume your volumetric efficiency is 100% (no losses). =20 IF you put a =BD =94 dia TB on you engine. You could have it wide open = and your engine (under normal prop load) probably wouldn=92t turn 4000 rpm. That = is because even wide open, the =BD=94 dia TB restricts airflow sufficiently = - that the manifold air density never approaches the ambient air density. = Since we know that the engine power is directly proportional to the density of = air in the combustion chamber =96 and this density is limited in this case to = less than ambient, you engine is not going to produce much power, certainly = not full power. So this bit of information tells us =93Bigger Lithium = Crystals, Scotty!!=94 =96 i.e try a larger throttle body.=20 =20 Now if you keep enlarging the diameter of the TB you would find that at fully open -your engine would be producing more power than it was, but perhaps still not the maximum power it is capable of. This is because = the air density in the manifold has increase due to the less restrictive = flow, but is still below ambient. This is due to the better, but still restrictive effect of the TB size on the air flow. Now if you continued enlarging the TB size, you would reach a point where with the TB just reaching fully open - your manifold air density is exactly ambient and = your engine is producing all the power it is going to. =20 Now if you enlarge the TB even further, you will simply find that you = can cause the manifold pressure (air density) to reach ambient without = opening the TB fully. Its simply large enough that all the air the engine can = use (ambient air density point) is met at partial throttle opening. In = fact , you can certainly continue to advance the throttle thereby opening the throttle plate even more =96 but, you are not going to increase the air density in the manifold and therefore you will not produce any = additional power for that additional throttle travel. =20 Bigger Throttle body=92s result in more power only up to the point the = airflow they permit causes manifold air density to reach ambient. Beyond that point, the only thing they do is provide frustration =96 by having all = that throttle travel remaining which does nothing to produce more power {:>). =20 Now if you can somehow lighten the load on your engine, then engine can turn faster providing more =93suction=94 on the manifold volume reducing = the air density below ambient, now opening your =93oversize=94 TB a bit more = will produce more power because you are increasing the airflow again to the = point where the equilibrium point between ambient air density in the manifold = and rpm is again reached. Lighten the load further and you can again = increase engine power by opening your TB more. Etc, etc. =20 =20 Ah, ain=92t this hobby wonderful {:>)=20 =20 =20 Ed =20 Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm =20 =20 __________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------=_NextPart_000_0003_01CABD83.598B7E80 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Actually, Mike, I do have a 68x72 Performance prop that I used for my 2.17 gear box.=A0 Don’t know = if that’s sufficiently different from yours to make a difference or not.=A0 Let me = know if interested – for the paltry sum of shipping costs, just might be = able to get it to you {:>).=A0 Don’t know if the blade profile will fit your = spinner cut our or not – that’s about the only problem I could = see.

 

Ed

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills
Sent: Saturday, March 06, = 2010 10:13 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = TB size, Travel and Power

 

Tracy,

 

Yes I have confirmed that I get full ambient = pressure at 2/3 (roughly) throttle near sea level. And yes I still have the POS = vacuum gauge. I know it needs replaced - just havent had the opportunity = yet.

 

My point in bringing this up yet again was to = emphasize the point Ed made a couple of posts back - that this whole thing is a = complex problem with a lot of variables. And to not dive in and start whacking = on the prop until certain that is where the problem is. In my case I'm not sure = it is. Full ambient MP at the TB doesn’t indicate how well the intake is = flowing and it is entirely possible to have full MP but a very poor performing = manifold. Guys in racing make lots of $ porting and flow testing = manifolds.

 

I need to make some changes to the intake anyway = for other reasons so I'm going to focus on that first. And once that's done, = if I'm still giving up some RPMs then I'll take a look at the prop. Unless of = course I can do it the easy way as Al suggested and borrow a prop. On that = note, are there any of you RV guys that have upgraded from the 2.17 gear ratio = to the 2.85 that have a "wrong way" prop you'd be willing to lend for = a test?

 

Meanwhile I havent been able to fly for the past 3 = weeks due to this crappy weather. Why's it always have to rain on the = weekends? Its not supposed to rain in SoCal at all.

 

Mike Wills

 

From: Tracy Crook

Sent: Saturday, March 06, 2010 7:06 AM

Subject: [FlyRotary] Re: TB size, Travel and Power

 

Mike,

   you are measuring the MP exactly where you should,   You can't do it properly anywhere else, at least not = with a simple instrument.

 

But are you at last confirming that you DO have full ambient MP = at 2/3 throttle setting?   That IS an important question if you want = to know the right answer to your question.    BTW, ditch the = vacuum gauge (if that's what you are using) and get a proper MP = gauge.

 

Tracy

On Fri, Mar 5, 2010 at 9:30 PM, Mike Wills <rv-4mike@cox.net> = wrote:

Ed,

 

 I hear what your saying (and I get = it). Here's the thing, and I admit I may have a misunderstanding here. Your explanation applies if you are measuring manifold pressure = essentially at the rotor face. If you measure MP closer to the TB as I do = unfortunately, it is possible to see ambient at full throttle but have restrictions in = the intake tract that would result in less than ambient at the rotor face. Conversely (and again theory - I'm open to being shown wrong here), a = properly designed DIE manifold would show ambient MP measured at the TB and = greater than ambient measured at the rotor face.

 

I accept that by trimming the prop I can lighten = the load and gain some HP (though some here seem to think that HP will increase = linearly with RPM to infinity and I don’t buy that either). But as you = alluded to in your previous, there's some potential for mistake in trimming any = prop until you are quite sure that you are not HP limited by something other = than load. And I'm not sure yet. Just a feeling based on the fact that I'm = using a cut down RX-7 TB that’s maxed out about 1/3 short of fully open. = And honestly I still havent dug any deeper because the airplane is flying well and has good performance. But sooner or later I'm going to want to get = more than the 5700RPM I'm currently getting - I want all the performance = that’s there.

 

Mike Wills

 

From: Ed Anderson

Sent: Friday, March 05, 2010 6:36 PM

Subject: [FlyRotary] TB size, Travel and Power

 

I am apparently not doing a very good job making the point about the = relationship between throttle body size, throttle travel and engine power = clear.  So here is another try at it - using extreme examples and no math.  = Let’s assume your volumetric efficiency is 100% (no = losses).

 

IF you put a =BD ” dia TB on you engine.  You could have it wide open and = your engine (under normal prop load) probably wouldn’t turn 4000 rpm.  = That is because even wide open, the =BD” dia TB restricts airflow sufficiently - = that the manifold air density never approaches the ambient air density.  = Since we know that the engine power is directly proportional to the density of = air in the combustion chamber – and this density is limited in this case = to less than ambient, you engine is not going to produce much power, certainly not = full power.  So this bit of information tells us “Bigger Lithium = Crystals, Scotty!!” – i.e  try a larger throttle body. =

 

Now if you keep enlarging the diameter of the TB you would find that at fully open = -your engine would be producing more power than it was, but perhaps still not = the maximum power it is capable of.  This is because the air density in = the manifold has increase due to the less restrictive flow, but is still = below ambient.  This is due to the better, but still restrictive effect = of the TB size on the air flow.  Now if you continued enlarging the TB = size, you would reach a point where with the TB just reaching fully open - your = manifold air density is exactly ambient and your engine is producing all the = power it is going to.

 

Now if you enlarge the TB even further, you will simply find that you can cause the manifold pressure (air density) to reach ambient without opening the TB fully.  Its simply large enough that all the air the engine can use (ambient air density point)  is met at partial throttle = opening.  In fact , you can certainly continue to advance the throttle thereby = opening the throttle plate even more – but, you are not going to increase the = air density in the manifold and therefore you will not produce any additional power = for that additional throttle travel.

 

Bigger Throttle body’s result in more power only up to the point the = airflow they permit causes manifold air density to reach ambient.  Beyond that = point, the only thing they do is provide frustration – by having all that = throttle travel remaining which does nothing to produce more power = {:>).

 

Now if you can somehow  lighten the load on your engine, then engine can turn = faster providing more “suction” on the manifold volume reducing the = air density below ambient, now opening your “oversize” TB a bit more will = produce more power because you are increasing the airflow again to the point where the = equilibrium point between ambient air density in the manifold and rpm is again reached.  Lighten the load further and you can again increase = engine power by opening your TB more. Etc, etc.

 

 

Ah, ain’t this hobby wonderful {:>)

 

 

Ed<= /p>

 

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com<= /p>

http://www.andersonee.com

http://www.dmack.net/mazda/index.html<= o:p>

http://www.flyrotary.com/<= /p>

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm=

 




__________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

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