X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from willowsprings.uwyo.edu ([129.72.10.31] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTPS id 3747820 for flyrotary@lancaironline.net; Tue, 07 Jul 2009 10:35:48 -0400 Received-SPF: none receiver=logan.com; client-ip=129.72.10.31; envelope-from=SBoese@uwyo.edu Received: from ponyexpress-ht1.uwyo.edu (ponyexpress-ht1.uwyo.edu [10.84.60.208]) by willowsprings.uwyo.edu (8.14.2/8.14.2) with ESMTP id n67EYtlP009811 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL) for ; Tue, 7 Jul 2009 08:35:01 -0600 (MDT) (envelope-from SBoese@uwyo.edu) Received: from Boesexps (172.26.4.5) by uwmail.uwyo.edu (10.84.60.198) with Microsoft SMTP Server id 8.1.375.2; Tue, 7 Jul 2009 08:34:58 -0600 From: sboese To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Muffler Date: Tue, 7 Jul 2009 08:34:53 -0600 Message-ID: <80511B89AC2341F6B9EF91EC32E3839C@gg.uwyo.edu> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002E_01C9FEDD.CD19D6E0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 ------=_NextPart_000_002E_01C9FEDD.CD19D6E0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable William, =20 Thanks for the link. I suspect I've seen most of that information at = one time or another, but it's nice to see it all in one place. =20 I don't think I've been running excessively rich. In cruise, I set the mixture to get about 60 degrees lean of peak EGT. This results in some decrease in power and the O2 sensors are both off-scale lean. For Take = off and climb and also in preparation for landing I set the mixture for = maximum power which is rich of peak but the engine is not operated under these conditions for long. Even idling, I find that running lean with about = 2-3 bars showing on the O2 meter seems to give the smoothest operation. =20 It's possible that I am running the engine too conservatively and thus = not hot enough to clean the plugs. Maybe I should simply use max power = mixture settings and WOT exclusively for awhile and see what that does. Well, = maybe not exclusively since that would make for some interesting taxiing. The = 103 gallons of fuel used in 15 hours gives an average of 7 gal/hr fuel consumption rate. Most of this time was in XC cruise. Only one 0.9 hr local flight was made during this period. =20 I agree that continuous combustion is not a reasonable theory. Ed's = idea of retarded ignition timing seems more probable whatever the mechanism for = that might be. =20 Steve Boese =20 =20 =20 =20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of William Wilson Sent: Monday, July 06, 2009 10:09 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Muffler =20 While the rotary design is a little more resistant to the onset of preignition, once it happens, the rotary is damaged just as easily as a piston engine or even more so. Drag racers suffering preignition have dismantled their motors and found rotors dented in from excess chamber pressure. It is possible that you have been having mild preignition not enough to damage the engine, I suppose. Do you suppose you have been running really excessively rich? That would also contribute to plug fouling, low power and low EGT. If you have fuel injection, a fuel map problem showing up only at high manifold pressures (higher than you = normally attain in your usual operating regime) maybe? You should get WAY more = than 10 hours on spark plugs even running 100LL. If combustion were still taking place as you speculate then it would = ignite the incoming mixture during the intake cycle and cause a backfire. So I think that is not it. I assume you've seen this but I found it interesting: http://www.wankel.org/74_Ignition/74-22%20Spark%20plug%20life%20.htm =20 =20 ------=_NextPart_000_002E_01C9FEDD.CD19D6E0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

William,

 

Thanks for the link.  I = suspect I’ve seen most of that information at one time or another, but it’s = nice to see it all in one place.

 

I don’t think I’ve been running excessively rich.  In cruise, I set the mixture to get = about 60 degrees lean of peak EGT.  This results in some decrease in power = and the O2 sensors are both off-scale lean.  For Take off and climb and also = in preparation for landing I set the mixture for maximum power which is = rich of peak but the engine is not operated under these conditions for = long.  Even idling, I find that running lean with about 2-3 bars showing on the O2 = meter seems to give the smoothest operation.

 

It’s possible that I am = running the engine too conservatively and thus not hot enough to clean the = plugs.  Maybe I should simply use max power mixture settings and WOT exclusively for = awhile and see what that does.  Well, maybe not exclusively since that = would make for some interesting taxiing.  The 103 gallons of fuel used in 15 = hours gives an average of 7 gal/hr fuel consumption rate.  Most of this = time was in XC cruise.  Only one 0.9 hr local flight was made during this = period.

 

I agree that continuous combustion = is not a reasonable theory.  Ed’s idea of retarded ignition timing = seems more probable whatever the mechanism for that might = be.

 

Steve Boese

   =  

 

 

 

-----Original = Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of William Wilson
Sent: Monday, July 06, = 2009 10:09 PM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: = Muffler

 

While the rotary design is a little more resistant to the onset of = preignition, once it happens, the rotary is damaged just as easily as a piston engine or = even more so.  Drag racers suffering preignition have dismantled their = motors and found rotors dented in from excess chamber pressure.  It is = possible that you have been having mild preignition not enough to damage the = engine, I suppose.  Do you suppose you have been running really excessively rich?  That would also contribute to plug fouling, low power and = low EGT.  If you have fuel injection, a fuel map problem showing up = only at high manifold pressures (higher than you normally attain in your usual operating regime) maybe?  You should get WAY more than 10 hours on = spark plugs even running 100LL.

If combustion were still taking place as you speculate then it would = ignite the incoming mixture during the intake cycle and cause a backfire.  So = I think that is not it.

I assume you've seen this but I found it interesting:
http://www.wankel.org/74_Ignition/74-22%20Spark%20plug%20life%20.htm=

 

 

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