X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-yx0-f180.google.com ([209.85.213.180] verified) by logan.com (CommuniGate Pro SMTP 5.4.4) with ESMTPS id 5411504 for flyrotary@lancaironline.net; Thu, 23 Feb 2012 08:04:29 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.213.180; envelope-from=rwstracy@gmail.com Received: by yenr11 with SMTP id r11so535207yen.25 for ; Thu, 23 Feb 2012 05:03:53 -0800 (PST) Received-SPF: pass (google.com: domain of rwstracy@gmail.com designates 10.101.128.17 as permitted sender) client-ip=10.101.128.17; Authentication-Results: mr.google.com; spf=pass (google.com: domain of rwstracy@gmail.com designates 10.101.128.17 as permitted sender) smtp.mail=rwstracy@gmail.com; dkim=pass header.i=rwstracy@gmail.com Received: from mr.google.com ([10.101.128.17]) by 10.101.128.17 with SMTP id f17mr736934ann.18.1330002233688 (num_hops = 1); Thu, 23 Feb 2012 05:03:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=subject:references:from:content-type:x-mailer:in-reply-to :message-id:date:to:content-transfer-encoding:mime-version; bh=k4ERNHax+ja1G3sXTXBLeVmOWrOLyeRhfgM84a2ddus=; b=pEhzvHPxQZ5NCse7k10bNGfqx6yojvKvJVyAh8ZN8glv+N8dosJ3hc8Xb+JLZwZDZg s1aIOzzPdPqEutuEASNTrffmgo14zeh3/fcWWKw5wZ7Ude14GDccQ5T7ALDTHEd8WUjQ xzSMkX/VRiPKQWEx4ls1r5dES7VeaYSQ/z2nk= Received: by 10.101.128.17 with SMTP id f17mr585062ann.18.1330002233542; Thu, 23 Feb 2012 05:03:53 -0800 (PST) Return-Path: Received: from [192.168.1.4] (172.sub-75-202-200.myvzw.com. [75.202.200.172]) by mx.google.com with ESMTPS id n24sm3492449yhj.13.2012.02.23.05.03.50 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 23 Feb 2012 05:03:52 -0800 (PST) Subject: Re: [FlyRotary] Re: Throttle Back Bobble References: From: Tracy Content-Type: multipart/alternative; boundary=Apple-Mail-11--492280345 X-Mailer: iPad Mail (8F191) In-Reply-To: Message-Id: <79A1DF05-3A86-4CDE-B772-7EA25BEBEDA0@gmail.com> Date: Thu, 23 Feb 2012 08:03:53 -0500 To: Rotary motors in aircraft Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (iPad Mail 8F191) --Apple-Mail-11--492280345 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii What Lynn said. Most newer cars cut the fuel in that condition and it DOES= eliminate the miss because the engine isn't even running. We don't want t= o go there because of the lack of lubrication. =20 But most of us pilots were taught to make all throttle changes smoothly and g= radually anyway. Slamming the throttle closed is considered bad form in an= airplane. We do need to deal with the situation where we are going downhi= ll at the end of a flight and the engine can be windmilling for significant p= eriods of time. We are in a special situation for two reasons. First is t= he lack of apex seal lubrication Lynn mentioned but also the limitation of t= he gear drive. The nylon snubber in the drive is not designed to absorb lon= g term reverse thrust when the engine windmills. I'm always conscious of m= aximizing the energy of altitude and descend with a small amount of power ra= ther than the drag of a windmilling prop. This maximizes fuel economy, keep= s the apex seals happy and keeps the torque going in the right direction in t= he gear drive. The number will be different for different airplanes but for= RVs a descent rate of around 300 fpm at 130 - 140 mph IAS works out well. P= lan ahead and watch the Vnav numbers on your GPS for when it's time to start= down. If you have an autopilot, program it for the appropriate numbers. = We don't fly 747s so throttle control is still up to you. Tracy Sent from my iPad On Feb 22, 2012, at 6:42 PM, Lehanover@aol.com wrote: > Closed throttle at high revs makes a good fuel burn (idle mixture) unlikel= y. The effective compression ratio drops to near zero due to poor cylinder f= illing. > =20 > Fuel molecules are very far apart. The stock Renesis maps up to 44 degree= of advance in this situation. The mixture burns very slowly requiring the a= dded advance (more time to burn). Popping and clicking is still burning mixt= ure lighting charges in the headers (turbo?) from chambers that didn't light= at all. (Misses). > =20 > In racing engines we didn't use the OMP and only premixed synthetic 2 cycl= e oil. So I jetted the idle mix real rich to keep the lube going in high rev= closed throttle moments. > =20 > The sheets of fire out the tail pipe was a crowd pleaser as well as the ex= plosions on gear changes. It didn't count against our 105 Db sound limit. > =20 > Lynn E. Hanover > =20 > In a message dated 2/22/2012 4:37:57 P.M. Eastern Standard Time, cbarber@t= exasattorney.net writes: > I had the same issue. I cut the fuel and added a bunch of advance for hig= h-rev/low-MP operations. Cleaned it right up. --Apple-Mail-11--492280345 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=utf-8
What Lynn said.   Most newer cars c= ut the fuel in that condition and it DOES eliminate the miss because the eng= ine isn't even running.   We don't want to go there because of the lack= of lubrication.   

But most of us pilots= were taught to make all throttle changes smoothly and gradually anyway. &nb= sp; Slamming the throttle closed is considered bad form in an airplane. &nbs= p; We do need to deal with the situation where we are going downhill at the e= nd of a flight and the engine can be windmilling for significant periods of t= ime.   We are in a special situation for two reasons.   First is t= he lack of apex seal lubrication Lynn mentioned but also the limitation of t= he gear drive.  The nylon snubber in the drive is not designed to absor= b long term reverse thrust when the engine windmills.   I'm always cons= cious of maximizing the energy of altitude and descend with a small amount o= f power rather than the drag of a windmilling prop.  This maximizes fue= l economy, keeps the apex seals happy and keeps the torque going in the righ= t direction in the gear drive.  The number will be different for differ= ent airplanes but for RVs a descent rate of around 300 fpm at 130 - 140 mph I= AS works out well.  Plan ahead and watch the Vnav numbers on your GPS f= or when it's time to start down.   If you have an autopilot, program it= for the appropriate numbers.   We don't fly 747s so throttle control i= s still up to you.

Tracy

Sent from my iPad

On Feb 22, 2012, at 6:42 PM, Lehanover@aol.com wrote:

Closed throttle at high revs makes a good fuel burn (idle mixture)=20 unlikely. The effective compression ratio drops to near zero due to poor=20 cylinder filling.
 
 Fuel molecules are very far apart. The stock Renesis maps up to 4= 4=20 degree of advance in this situation. The mixture burns very slowly requiring= the=20 added advance (more time to burn). Popping and clicking is still burning mix= ture=20 lighting charges in the headers (turbo?) from chambers that didn't light at a= ll.=20 (Misses).
 
In racing engines we didn't use the OMP and only premixed synthetic 2 c= ycle=20 oil. So I jetted the idle mix real rich to keep the lube going in high rev=20= closed throttle moments.
 
The sheets of fire out the tail pipe was a crowd pleaser as well as the= =20 explosions on gear changes. It didn't count against our 105 Db  sound=20= limit.
 
Lynn E. Hanover
 
In a message dated 2/22/2012 4:37:57 P.M. Eastern Standard Time,=20 cbarber@texasattorney.net w= rites:
I had=20 the same issue.  I cut the fuel and added a bunch of advance for=20 high-rev/low-MP operations.  Cleaned it right=20 up.
= --Apple-Mail-11--492280345--