X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from qw-out-2122.google.com ([74.125.92.27] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3747388 for flyrotary@lancaironline.net; Tue, 07 Jul 2009 00:09:25 -0400 Received-SPF: pass receiver=logan.com; client-ip=74.125.92.27; envelope-from=fluffysheap@gmail.com Received: by qw-out-2122.google.com with SMTP id 3so1675302qwe.25 for ; Mon, 06 Jul 2009 21:08:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=pNboBhaxoPSbMKKlyik+HOdw7ah0bnCvOFGKD5J+2jQ=; b=QtoIitql/Tv5ozzyaYS2kx8ngoesEAOEx4T6vVxfjMDaDYRYXAWhKgMqg+b8ekipZW UbcjdFSFEHnX/DPX5YT0LH6zzjyJ4LZzrpDucGT4UweMJvdq5vaBZKG61NLYUJF6zP58 r8LvXFETnI2c01a632a4DBELDO22B8AQgoVdk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=Gnk8YAmkoqDrHlE4adFGdpUw2czg5Wx4yU9YO5Bkjibqk6Seg7Z2f21+T7089lvAVE x3nmsyU9Xkh7viOHVnhk4NUuGYKcrheJDHRzjyVbsOwMGROfMo+pvw7rkxAFa8EDe8Ph EQ6XXk/jBJeGDH53sbz6VmhyqYa8sv+byV3tQ= MIME-Version: 1.0 Received: by 10.224.45.141 with SMTP id e13mr5993098qaf.218.1246939727731; Mon, 06 Jul 2009 21:08:47 -0700 (PDT) In-Reply-To: References: Date: Mon, 6 Jul 2009 21:08:47 -0700 Message-ID: Subject: Re: [FlyRotary] Re: Muffler From: William Wilson To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=0015175caa2a871b7b046e15c7f8 --0015175caa2a871b7b046e15c7f8 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable 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 normall= y 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 On Mon, Jul 6, 2009 at 7:17 PM, Steven Boese wrote: > I never found the broken muffler part in the outlet of the muffler where > it might have caused increased back pressure even though it was possible = for > it to end up in that location by standing the muffler on its end. The > symptoms after repairing the muffler were the same as before the repair w= as > made so at this point, I don=92t think the broken part was a factor in th= e > performance issue. Looking back at the data log, the #2 rotor EGT droppe= d > by about 250 degrees during the power deficit. Back pressure would > probably affect both rotors in a similar fashion so that would also point= to > SAG as the culprit. > > > > In response to your and Bobby=92s questions, at the onset of SAG, there w= ere > a total of 15 hours on the plugs, 106 gal total of fuel burned, 53 gal of > that was 100LL. > > > > Ed is most likely right that operating at the increased manifold pressure > available at low altitude made the SAG show up while it didn=92t at lower > manifold pressures that I normally see. > > > > The relatively small amount of time and fuel that the plugs had seen when > SAG occurred may also be due to the low power levels and correspondingly > lower combustion temperatures permitting more rapid lead deposition on th= e > plugs. It looks like I should routinely change plugs every 10 hours or > so. I did have extra plugs along on the Texas trip and it would have bee= n > easy to have installed them at the rotorfest. > > > > The nature of SAG is puzzling. The symptoms of decreased EGT, decreased > power output, and increased heat transfer to the oil and coolant are all > consistent with descriptions of pre-ignition more than that of spark plug > misfire. In piston engines, pre-ignition can rapidly lead to destruction= , > but the rotary engine may be more tolerant of it. Maybe it isn=92t a mat= ter > of no ignition due to the spark plug not firing, but a matter of the fire > not going out between sparks. The lead in 100LL increases the octane > rating by slowing the combustion rate and thereby decreasing the tendency > for detonation. Maybe there is enough gas phase lead in the vicinity of > the spark plug with lead deposited on it that the combustion rate is slow= ed > enough to persist from one cycle to the next while the normal combustion > rate occurs in the rest of the chamber. This could result in a process > similar to pre-ignition. This theory probably has as much probability of > being right as the one I had concerning the apex seals clicking. > > > > Maybe I can accumulate a pile of SAGGING spark plugs as big as Ed=92s. T= hat > would be verifiable at least. > > > > Steve Boese > > > > > > > > -----Original Message----- > *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] *O= n > Behalf Of *Todd Bartrim > *Sent:* Monday, July 06, 2009 6:23 PM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: Muffler > > > > Hi Steve; > So you now assume that your power loss is directly attributable to SA= G > and not to the partially blocked muffler? Is this correct? > I'm curious as I also use a homemade muffler (SpinTech copy) and hav= e > wondered what the result would be if any of the internal came loose. I > wonder if your increased backpressure contributed to the onset of SAG? An= d > do you only burn 100LL, occasionally, or never? > > > > > Todd > C-FSTB > RV9 Turbo13B > > > --0015175caa2a871b7b046e15c7f8 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable While the rotary design is a little more resistant to the onset of preignit= ion, once it happens, the rotary is damaged just as easily as a piston engi= ne or even more so.=A0 Drag racers suffering preignition have dismantled th= eir motors and found rotors dented in from excess chamber pressure.=A0 It i= s possible that you have been having mild preignition not enough to damage = the engine, I suppose.=A0 Do you suppose you have been running really exces= sively rich?=A0 That would also contribute to plug fouling, low power and l= ow EGT.=A0 If you have fuel injection, a fuel map problem showing up only a= t high manifold pressures (higher than you normally attain in your usual op= erating regime) maybe?=A0 You should get WAY more than 10 hours on spark pl= ugs even running 100LL.

If combustion were still taking place as you speculate then it would ig= nite the incoming mixture during the intake cycle and cause a backfire.=A0 = 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<= /a>

On Mon, Jul 6, 2009 at 7:17 PM, Steve= n Boese <sboese@uwy= o.edu> wrote:

I never found the broken muffler p= art in the outlet of the muffler where it might have caused increased back pressur= e even though it was possible for it to end up in that location by standing t= he muffler on its end.=A0 The symptoms after repairing the muffler were the same as before the repair was made so = at this point, I don=92t think the broken part was a factor in the performance issue.=A0 Looking back at the data log, the #2 rotor EGT dropped by about 250 degrees during the power deficit= . =A0Back pressure would probably affect both rotors in a similar fashion so that would also point to SAG as the culprit.=

=A0

In response to your and Bobby=92s questions, at the onset of SAG, there were a total of 15 hours on the plugs= , 106 gal total of fuel burned, 53 gal of that was 100LL.

=A0

Ed is most likely right that opera= ting at the increased manifold pressure available at low altitude made the SAG show= up while it didn=92t at lower manifold pressures that I normally see.

=A0

The relatively small amount of tim= e and fuel that the plugs had seen when SAG occurred may also be due to the low p= ower levels and correspondingly lower combustion temperatures permitting more ra= pid lead deposition on the plugs.=A0 It looks like I should routinely change plugs every 10 hours or so. =A0<= /span>I did have extra plugs along on the Texas trip and it would have been easy to have installed them at the roto= rfest.

=A0

The nature of SAG is puzzling.=A0 The symptoms of decreased EGT, decreased power output, and increased heat transfer to the oil and coolant are all consistent with descriptions of pre-ignition more than that of spark plug misfire.=A0 In piston engines, pre-ignition can rapidly lead to destruction, but the rotary engine may be more tolerant= of it.=A0 Maybe it isn=92t a matter of no ignition due to the spark plug not firing, but a matter of the fire n= ot going out between sparks.=A0 The lead in 100LL increases the octane rating by slowing the combustion rate and the= reby decreasing the tendency for detonation.=A0 Maybe there is enough gas phase lead in the vicinity of the spark pl= ug with lead deposited on it that the combustion rate is slowed enough to pers= ist from one cycle to the next while the normal combustion rate occurs in the r= est of the chamber. This could result in a process similar to pre-ignition.=A0 This theory probably has as much probability of being right as the one I had concerning the apex seals click= ing.

=A0

Maybe I can accumulate a pile of S= AGGING spark plugs as big as Ed=92s.=A0 That would be verifiable at least.=A0 =A0=A0=A0<= /span>

=A0

Steve Boese =A0=

=A0

=A0 =A0

=A0

-----Origina= l Message-----
From: Rotary motors in air= craft [mailto:fl= yrotary@lancaironline.net] On Behalf Of Todd Bartrim
Sent: Monday, July 06, 200= 9 6:23 PM
To: Rotary motors in aircr= aft
Subject: [FlyRotary]= Re: Muffler

= =A0

= Hi Steve;
=A0=A0=A0 So you now assume that your power loss is directly attributable to SAG and not to the partially blocked muffler? Is this corre= ct?
=A0=A0=A0=A0 I'm curious as I also use a homemade muffler (SpinTech copy) and have wondered what the result would be if any of the internal cam= e loose. I wonder if your increased backpressure contributed to the onset of = SAG? And do you only burn 100LL, occasionally, or never?


= =A0

Todd
C-FSTB
RV9 Turbo13B

= =A0


--0015175caa2a871b7b046e15c7f8--