From: marv@lancair.net
Subject: Re: Engine Dyno
To: <lml@lancaironline.net>
Date: Fri, 02 Mar 2007 15:29:03 -0500
Message-ID: <web-1879136@logan.com>
In-Reply-To: <7B15876C7CF8F84CA9386211A9DD224901524A@bpaserver.BPAENGINES.local>
References: <7B15876C7CF8F84CA9386211A9DD224901524A@bpaserver.BPAENGINES.local>
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Posted for "Monty Barrett Sr" <MONTY@BPAENGINES.COM>:

  RE: Archived message #40455-
  
  
  Quoting out of context--------
  
  
  ----one engine builder makes a lot of money rebuilding magnetos.  Not true.
  A person rebuilding magnetos and trying to make money on it will go broke.
  He has to do
  
  other profitable procedures to stay in business.  One of those procedures is
NOT to use products that have unknown characteristics, have little or no
technical support,
  
  and give you problems on a large percentage basis.  Translation:  almost ½
the EI systems we have attempted to operate in test cell have failed within a
few minutes of startup.
  
  
  I agree, that under CERTAIN conditions there is an advantage to an ignition
system that has a CONTROLLED advance curve that can position the ignition
event at the PROPER time with a less than full power operation.   The key
words in the previous sentence are CONTROLLED and PROPER.  No EI system on the
market at the present time meets those 2 requirements to my knowledge.  BMEP
produces the power but it does NOT address PEAK CYLINDER PRESSURES and at what
  
  Crank angle they occur.  There is a finite limit to maximum allowable peak
cylinder pressure.  There are 3 ways to control the peak pressure:
  
  1.	retard the ignition event
  2.	a proper change in the combustible mixture
  3.	decrease the manifold pressure
  
  
  It should be evident that the only parameter the pilot CANNOT CONTROL in
flight is #1.  The #2 method has to be accurately done and is not understood
by very many people.
  
  
  A preset advance curve designed for a compression ratio of 8.5:1 is not
proper for a compression ratio of 10.5:1 in the same engine and operating
conditions.  An advance curve that considers manifold pressure only is
seriously flawed.  Consider this:  What is the MAP immediately after startup ?
  Ans:  relatively low.  What does the ignition do with low MAP ?  Ans:
Advances.  What is the result of advance ignition at idling and taxi speeds?
  Ans:  A larger area is exposed to the heat of combustion which does nothing
but increase the CHT.  This happens while you're on the ground.  Exactly what
you want, right ?
  
  
  Until the above criteria are addressed by the EI manufactures in a proper 
and
documented method, BPE Inc. will not recommend, sell or install EI.
  
  
  Monty Barrett
  
  BPE Inc.