X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 29 May 2007 17:13:08 -0400 Message-ID: X-Original-Return-Path: Received: from web36605.mail.mud.yahoo.com ([209.191.85.22] verified) by logan.com (CommuniGate Pro SMTP 5.1.9) with SMTP id 2073511 for lml@lancaironline.net; Tue, 29 May 2007 16:57:45 -0400 Received-SPF: none receiver=logan.com; client-ip=209.191.85.22; envelope-from=wfhannahan@yahoo.com Received: (qmail 97985 invoked by uid 60001); 29 May 2007 20:57:06 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:Date:From:Subject:To:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-ID; b=fwTPe16X7+5KUlNGjWuZNKWyLF3Y/oE5QXvM/6J6mtxOtyD9LLcdl/hDdeNumzbNKlIP6OWKfaDNzzF8fCReAkHfvwJb+OEu/i4hyjnv1AOUBIj8Xo84THna5lmQfkdEuOSCw5kRgdDvIB6/kjV1CO0jAIKZ63Ly0hbox2AdUqE=; X-YMail-OSG: W8dT4ecVM1kF7jEMTUsAWsDxLXW8mCEhi_U3i.BcoCHbQMm9Q.UVP3pAnbwH7h45LKwG7EYiHciY1nhqaCKxsAv0JAHNVwvxPe2g6XVKv6ouuY5LjhQ9nP8lZrF3TA-- Received: from [71.208.29.60] by web36605.mail.mud.yahoo.com via HTTP; Tue, 29 May 2007 13:57:06 PDT X-Original-Date: Tue, 29 May 2007 13:57:06 -0700 (PDT) From: Bill Hannahan Subject: TSIO 550 LOP X-Original-To: MAIL LANCAIR MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1743492778-1180472226=:97284" Content-Transfer-Encoding: 8bit X-Original-Message-ID: <271765.97284.qm@web36605.mail.mud.yahoo.com> --0-1743492778-1180472226=:97284 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit TRUE < This results in more expansion = lower EGT.> NOT TRUE Imagine the timing advanced to 60 deg before top dead center. This allows more time for fuel and air to burn before tdc resulting in higher cylinder temperature and pressure and a higher rate of heat transfer into the cylinder and head. If the engine is operating at high MP the fuel air mixture may detonate, spiking temperature, pressure and heat transfer rates even higher. After TDC the combustion products expand over the full CR and cool by Boyle’s law. The fuel releases a fixed amount of energy, and since more of it flows into the cylinder head there is less energy in the exhaust gas. Under normal operating conditions fuel continues to burn after TDC, so pressure and temp do not drop as fast as Boyle's law predicts. More advance means less fuel available to burn after TDC. --------------------------------- Yahoo! oneSearch: Finally, mobile search that gives answers, not web links. --0-1743492778-1180472226=:97284 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: 8bit
 
<RPM:
Higher RPM move the EFFECTIVE timing closer to TDC.>
 
TRUE
 
 < This results in more expansion = lower EGT.>
 
NOT TRUE
 
Imagine the timing advanced to 60 deg before top dead center. This allows more time for fuel and air to burn before tdc resulting in higher cylinder temperature and pressure and a higher rate of heat transfer into the cylinder and head.
 
If the engine is operating at high MP the fuel air mixture may detonate, spiking temperature, pressure and heat transfer rates even higher.
 
After TDC the combustion products expand over the full CR and cool by Boyle’s law. The fuel releases a fixed amount of energy, and since more of it flows into the cylinder head there is less energy in the exhaust gas.
 
Under normal operating conditions fuel continues to burn after TDC, so pressure and temp do not drop as fast as Boyle's law predicts. More advance means less fuel available to burn after TDC.
 
 
 
 

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