X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from omr-m10.mx.aol.com ([64.12.143.86] verified) by logan.com (CommuniGate Pro SMTP 6.0.5) with ESMTPS id 6398906 for flyrotary@lancaironline.net; Wed, 31 Jul 2013 20:04:06 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.143.86; envelope-from=shipchief@aol.com Received: from mtaout-ma04.r1000.mx.aol.com (mtaout-ma04.r1000.mx.aol.com [172.29.41.4]) by omr-m10.mx.aol.com (Outbound Mail Relay) with ESMTP id E2A02700EE2C1 for ; Wed, 31 Jul 2013 20:03:29 -0400 (EDT) Received: from [10.240.81.35] (78.sub-174-239-197.myvzw.com [174.239.197.78]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by mtaout-ma04.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPSA id D6726E00010B for ; Wed, 31 Jul 2013 20:03:22 -0400 (EDT) Subject: Re: [FlyRotary] Fwd: [FlyRotary] Re: : Misfire References: From: Scott Emery Content-Type: multipart/alternative; boundary=Apple-Mail-4--276275344 X-Mailer: iPhone Mail (8E600) In-Reply-To: Message-Id: Date: Wed, 31 Jul 2013 17:03:12 -0700 To: Rotary motors in aircraft Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (iPhone Mail 8E600) x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1375315408; bh=3XHvotis44hLGEqsdAJQocke/0GdbktNqRlZcsEFoc4=; h=From:To:Subject:Message-Id:Date:Mime-Version:Content-Type; b=HPVlOvb2NhcskWbzaxymYCP5jAljEM92W3xYScueFbznLj8invaUUUHYsrQBN7uNc WwHtC6ptZQa1csmH8KKjD5JekP49gMkffeeqpk3RY23f6dzQke2y6Kx5fIvJunhaiG u2bmoVMro4pN/+Ljcj9HMBOP/FTVn15McZR4xMKQ= x-aol-sid: 3039ac1d290451f9a5c93f8e X-AOL-IP: 174.239.197.78 --Apple-Mail-4--276275344 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii So my engine may have detonated simply because the engine builder opened up t= he upper (trailing) spark plug holes to improve the redundant dual ignition i= dea of an aircraft engine? As rpm and boost increased the compression of the intake charge? The fire co= uld jump the apex seal at the big hole and light the leading edge of the int= ake charge just as the intake ports are closing?! Sent from my iPhone On Jul 30, 2013, at 11:16 AM, Lehanover@aol.com wrote: > In a message dated 7/30/2013 1:36:12 P.M. Eastern Daylight Time, Lehanover= @aol.com writes: > The rotary has three features that make for a poor idle compared to a pist= on engine. > =20 > Heat of compression. > The rise in chamber temperature caused by compressing the fuel/air mixture= . > The rotary has poor heat of compression because of the large surface are o= f the chamber, and much of the chamber surface is cooled. Low heat of compre= ssion allows fuel droplets to condense on the chamber surfaces and the engin= e sees this as a mixture that is too lean to light. > =20 > Compression leakage: > The rotor face has many end gaps through which it leaks compression. > =20 > For example, on NA rotaries I gap the side seal to corner seal at zero. So= long as the combination of two side seals and the joining corner seal pop b= ack up when depressed and released, that is sufficient. The zero gap will be= come a measurable gap shortly after break in. Overly wide end gaps lead to l= eakage of compression, and that leads to lowered heat of compression as abov= e. > =20 > Effective compression ratio: > =20 > At idle and near idle, the amount of air allowed into the engine is minima= l. So the computer limits the injection pulse width accordingly.So the cylin= der filling is minimal, and so heat of compression is minimal. > =20 > So, if the same amount of cylinder filling is used. The rotor with the hig= her compression ratio will generate fewer misses and a smoother idle. Becaus= e for a fixed cylinder filling number, the higher compression rotor produces= the highest heat of compression.=20 > =20 > Higher heat of compression means better fuel vaporization and a more thoro= ugh burn. > =20 > A misfire is an event wherein a dose or part of a dose of mixture was not l= ighted at or near the correct time during the cycle. > A misfire that involves no burned mixture is a noticeable event, in that t= he engine will be out of balance for that cycle. The engine will wiggle in i= ts mount. A misfire that involves a trailing plug will not be noticed at or n= ear idle. A misfire that involves the leading plug can be noticed by the ver= y attentive. > =20 > A popping sound in the headers or exhaust in general with no engine wiggle= is more likely a small air leak in the header, that allows oxygen to mix in= the header with some as yet unburned fuel. The popping is this mixture igni= ting. Very likely to be experienced on long closed throttle descents. > =20 > A misfire at higher throttle settings and full power, will be very noticea= ble, as an unlighted charge between two lighted charges will produce quite a= n imbalance jerk in the engine, and the mixture from the misfire will light i= n the header right outside the engine. So you get a jerk and a loud change i= n engine tone. > This does not damage the engine, but can damage the exhaust system and, or= , ruin a muffler. As has been seen, a damaged muffler can stop an engine or r= educe it's power out put to useless levels. > =20 > Lynn E. Hanover > =20 > =20 > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List= .html --Apple-Mail-4--276275344 Content-Transfer-Encoding: 7bit Content-Type: text/html; charset=utf-8
So my engine may have detonated simply because the engine builder opened up the upper (trailing) spark plug holes to improve the redundant dual ignition idea of an aircraft engine?
As rpm and boost increased the compression of the intake charge? The fire could jump the apex seal at the big hole and light the leading edge of the intake charge just as the intake ports are closing?!

Sent from my iPhone

On Jul 30, 2013, at 11:16 AM, Lehanover@aol.com wrote:

In a message dated 7/30/2013 1:36:12 P.M. Eastern Daylight Time, Lehanover@aol.com writes:
The rotary has three features that make for a poor idle compared to a piston engine.
 
Heat of compression.
The rise in chamber temperature caused by compressing the fuel/air mixture.
The rotary has poor heat of compression because of the large surface are of the chamber, and much of the chamber surface is cooled. Low heat of compression allows fuel droplets to condense on the chamber surfaces and the engine sees this as a mixture that is too lean to light.
 
Compression leakage:
The rotor face has many end gaps through which it leaks compression.
 
For example, on NA rotaries I gap the side seal to corner seal at zero. So long as the combination of two side seals and the joining corner seal pop back up when depressed and released, that is sufficient. The zero gap will become a measurable gap shortly after break in. Overly wide end gaps lead to leakage of compression, and that leads to lowered heat of compression as above.
 
Effective compression ratio:
 
At idle and near idle, the amount of air allowed into the engine is minimal. So the computer limits the injection pulse width accordingly.So the cylinder filling is minimal, and so heat of compression is minimal.
 
So, if the same amount of cylinder filling is used. The rotor with the higher compression ratio will generate fewer misses and a smoother idle. Because for a fixed cylinder filling number, the higher compression rotor produces the highest heat of compression. 
 
Higher heat of compression means better fuel vaporization and a more thorough burn.
 
A misfire is an event wherein a dose or part of a dose of mixture was not lighted at or near the correct time during the cycle.
A misfire that involves no burned mixture is a noticeable event, in that the engine will be out of balance for that cycle. The engine will wiggle in its mount. A misfire that involves a trailing plug will not be noticed at or near idle. A misfire that involves the leading plug can be noticed by the very attentive.
 
A popping sound in the headers or exhaust in general with no engine wiggle is more likely a small air leak in the header, that allows oxygen to mix in the header with some as yet unburned fuel. The popping is this mixture igniting. Very likely to be experienced on long closed throttle descents.
 
A misfire at higher throttle settings and full power, will be very noticeable, as an unlighted charge between two lighted charges will produce quite an imbalance jerk in the engine, and the mixture from the misfire will light in the header right outside the engine. So you get a jerk and a loud change in engine tone.
This does not damage the engine, but can damage the exhaust system and, or, ruin a muffler. As has been seen, a damaged muffler can stop an engine or reduce it's power out put to useless levels.
 
Lynn E. Hanover
 
 
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