X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao104.cox.net ([68.230.241.42] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3882402 for flyrotary@lancaironline.net; Sun, 11 Oct 2009 12:45:56 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.42; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao104.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20091011164516.RMPM14181.fed1rmmtao104.cox.net@fed1rmimpo03.cox.net> for ; Sun, 11 Oct 2009 12:45:16 -0400 Received: from wills ([68.105.87.66]) by fed1rmimpo03.cox.net with bizsmtp id rUlE1c0081RstZw04UlGid; Sun, 11 Oct 2009 12:45:16 -0400 X-VR-Score: -120.00 X-Authority-Analysis: v=1.0 c=1 a=0iCzXv5dXLIA:10 a=3oc9M9_CAAAA:8 a=kviXuzpPAAAA:8 a=Ia-xEzejAAAA:8 a=N8B9JuSIAAAA:8 a=po2gix3cmvpKoZgZWCEA:9 a=ZCzR2pOZzNiJGj12a94A:7 a=RYiLRPxd8HfcHHh4hANW1JCQoe0A:4 a=U8Ie8EnqySEA:10 a=4vB-4DCPJfMA:10 a=EzXvWhQp4_cA:10 a=pE5wq8uS0gr6O0r3:21 a=muE7RcxC6S0JpHUS:21 a=pGLkceISAAAA:8 a=Rx5NZLHd_x9o_q6wrLAA:9 a=Kcy0xUgyizkLOIpsRg4A:7 a=qiMzlrux0mBi-jPZmUCPgYe70Y0A:4 a=MSl-tDqOz04A:10 X-CM-Score: 0.00 Message-ID: From: "Mike Wills" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: where's the missing power? Date: Sun, 11 Oct 2009 09:45:15 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0030_01CA4A57.89086780" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_0030_01CA4A57.89086780 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Dave, Thanks for the info and offer. I want to take you up on it sometime, = but cant make it this week. Mike ----- Original Message -----=20 From: David Leonard=20 To: Rotary motors in aircraft=20 Sent: Saturday, October 10, 2009 11:48 PM Subject: [FlyRotary] Re: where's the missing power? Mike, The last couple of inches of my throttle don't give me much power = difference either, for what it is worth. I can't believe thay you have = not been up in my plane yet. I have this coming week off if you have = any time... Dave On Sat, Oct 10, 2009 at 11:14 PM, wrote: Mike, There are several reasons that an engine will produce max power at = "less" than full throttle. First, and this can sometimes be hard to = check, be sure that your full throttle position doesn't rotate the = throttle plate past full open. I've seen this several times in butterfly = throttle systems. If you are using a Mazda throttle body it is likely = that the wide open position is controlled with a stop. You shouldn't = have a over rotation problem with that. The second reason, and far more = common, is that the design has more intake than it can use with the = tuning or RPM that the prop limits it to. This isn't really a problem = other than indicating that with development the engine could make more = power. Often with the design constraints placed on us by a close fitting = cowling or restrictive exhaust limit the best airflow to less than the = throttle body can pass. The engine just can't "breathe" well enough to = need a larger opening. The length of the intake or exhaust can be too = long/short and the maximum amount of air that the engine can digest will = be at the 3/4 throttle area or even less. Most engines can be tuned to = best performance at a specific length inlet and the diameter is also = important. Same with the exhaust. If either system is off a significant = amount it can prevent you from making any more power past a given = throttle opening. This won't hurt the engine at all, it just shows you = that some portion of the system can be improved. If your exhaust gas = temperature is correct then the injection is working properly and you = need to check the other systems. Be sure to double check your exhaust = for obstructions or a pipe collapse. We have had too many exhaust = problems lately. To put your self at ease remember this, most modern = diesels have NO throttle plate. The speed of the engine is completely = controlled by the amount of fuel injected. This helps the efficiency at = maximum throttle, but obviously there is more air than the engine can = use at low speeds. A small amount of fuel is injected, compression = ignited ,and all burns up. If all is healthy your engine is drawing all = the air you can use by half throttle. You can probably make improvements = and get more power or lower fuel burn by tuning. Bill Jepson=20 -----Original Message----- From: Mike Wills To: Rotary motors in aircraft Sent: Sat, Oct 10, 2009 8:27 pm Subject: [FlyRotary] where's the missing power? I noticed quite a while ago and have mentioned several times here = that my engine does not have a linear response to throttle. It reaches = its max power before it reaches fully open throttle. I havent worried = too much about this up until now because the airplane has sufficient = power as is, has slightly better performance than my previous 160HP Lyc = powered -6A, and my wood prop is actually a pretty good match for the = current power level. But I would like to understand what's going on here and eventually = address it. I was flying yesterday, my usual boring holes in the sky = directly over the airport. Decided to investigate just a little so = leveled at 5,000 feet at full throttle. Started reducing throttle until = I noticed a slight reduction in RPM and fuel flow. Then looked down at = where the throttle was actually set and was shocked to see it slightly = below half open. I dont have a regular manifold pressure gauge, just an = industrial type vacuum gauge ( I really gotta get an MP gauge). Anyway, = the vacuum gauge was indicating 4" of vacuum. So I suspect I am giving up a substantial amount of HP. I think the = most likely suspect is my throttle body. For a throttle body I copied = Tracy's original design. Started with a stock late 80s Mazda TB and = hacked off the third port and all of the extra stuff. The cowl in this = area is very tight and I am unable to install any sort of air filter or = any sort of bell mouth on the TB. And I'm sure the cowl's close = proximity to the TB influences airflow into it as well. Any comments on this or ways to test it are welcome. Mike Wills RV-4 N144MW --=20 David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net ------=_NextPart_000_0030_01CA4A57.89086780 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Dave,
 
 Thanks for the info and offer. I = want to take=20 you up on it sometime, but cant make it this week.
 
Mike
----- Original Message -----
From:=20 David=20 Leonard
Sent: Saturday, October 10, = 2009 11:48=20 PM
Subject: [FlyRotary] Re: = where's the=20 missing power?

Mike,
 
The last couple of inches of my throttle don't give me much power = difference either, for what it is worth.  I can't believe thay = you have=20 not been up in my plane yet.  I have this coming week off if you = have any=20 time...
 
Dave

On Sat, Oct 10, 2009 at 11:14 PM, <wrjjrs@aol.com> = wrote:
Mike,
There are several reasons that an engine will produce max power = at=20 "less" than full throttle. First, and this can sometimes be hard to = check,=20 be sure that your full throttle position doesn't rotate the throttle = plate=20 past full open. I've seen this several times in butterfly throttle = systems.=20 If you are using a Mazda throttle body it is likely that the wide = open=20 position is controlled with a stop. You shouldn't have a over = rotation=20 problem with that. The second reason, and far more common, is that = the=20 design has more intake than it can use with the tuning or RPM that = the prop=20 limits it to. This isn't really a problem other than indicating that = with=20 development the engine could make more power. Often with the design=20 constraints placed on us by a close fitting cowling or restrictive=20 exhaust limit the best airflow to less than the throttle body = can pass.=20 The engine just can't "breathe" well enough to need a larger=20 opening. The length of the intake or exhaust can be too = long/short and=20 the maximum amount of air that the engine can digest will be at the = 3/4=20 throttle area or even less. Most engines can be tuned to best = performance at=20 a specific length inlet and the diameter is also important. Same = with the=20 exhaust. If either system is off a significant amount it can prevent = you=20 from making any more power past a given throttle opening. This won't = hurt=20 the engine at all, it just shows you that some portion of the system = can be=20 improved. If your exhaust gas temperature is correct then the = injection is=20 working properly and you need to check the other systems. Be sure to = double=20 check your exhaust for obstructions or a pipe collapse. We have had = too many=20 exhaust problems lately. To put your self at ease remember this, = most modern=20 diesels have NO throttle plate. The speed of the engine is = completely=20 controlled by the amount of fuel injected. This helps the efficiency = at=20 maximum throttle, but obviously there is more air than the engine = can use at=20 low speeds. A small amount of fuel is injected, compression ignited = ,and all=20 burns up. If all is healthy your engine is drawing all the air you = can use=20 by half throttle. You can probably make improvements and get more = power or=20 lower fuel burn by tuning.
Bill Jepson=20


-----Original Message-----
From: Mike = Wills <rv-4mike@cox.net>
To:=20 Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Sat, = Oct 10, 2009=20 8:27 pm
Subject: [FlyRotary] where's the missing=20 power?

I noticed quite a while ago and = have mentioned=20 several times here that my engine does not have a linear response to = throttle. It reaches its max power before it reaches fully open = throttle. I=20 havent worried too much about this up until now because the airplane = has=20 sufficient power as is, has slightly better performance than my = previous=20 160HP Lyc powered -6A, and my wood prop is actually a pretty good = match for=20 the current power level.
 
But I would like to understand = what's going on=20 here and eventually address it. I was flying yesterday, my usual = boring=20 holes in the sky directly over the airport. Decided to investigate = just a=20 little so leveled at 5,000 feet at full throttle. Started reducing = throttle=20 until I noticed a slight reduction in RPM and fuel flow. Then looked = down at=20 where the throttle was actually set and was shocked to see it = slightly below=20 half open. I dont have a regular manifold pressure gauge, just an = industrial=20 type vacuum gauge ( I really gotta get an MP gauge). Anyway, the = vacuum=20 gauge was indicating 4" of vacuum.
 
So I suspect I am giving up a = substantial=20 amount of HP. I think the most likely suspect is my throttle body. = For a=20 throttle body I copied Tracy's original design. Started with a = stock=20 late 80s Mazda TB and hacked off the third port and all of the extra = stuff.=20 The cowl in this area is very tight and I am unable to install any = sort of=20 air filter or any sort of bell mouth on the TB. And I'm sure the = cowl's=20 close proximity to the TB influences airflow into it as = well.
 
Any comments on this or ways to = test it are=20 welcome.
 
Mike Wills
RV-4=20 N144MW



--
David Leonard

Turbo Rotary RV-6 = N4VY
http://N4VY.RotaryRoster.nethttp://RotaryRoster.net
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