Mailing List lml@lancaironline.net Message #43878
From: Walter Atkinson <walter@advancedpilot.com>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] FW: Engine efficiency
Date: Fri, 31 Aug 2007 13:28:03 -0400
To: <lml@lancaironline.net>
Fred:

I *think* the number is 15.6, not 16.6.  That would certainly make a lot more sense.

Walter



On Aug 31, 2007, at 6:19 AM, John Barrett wrote:

 

 

From: Fred Moreno [mailto:fredmoreno@optusnet.com.au]
Sent: Thursday, August 30, 2007 6:58 PM
To: John Barrett
Subject: FW: Engine efficiency

 

Hi John:

 

Please forward the note below to LML as it is rejecting my emails again after a brief run of acceptance.

 

Cheers,

 

Fred

___________________________________________________________________

 

 

“The

  Continental engine manual doesn't seem relevant with the high compression.

  On the other hand, I did get data from APS/GAMI on operation LOP. For 10:1

  compression the HP = 16.6 x FF(gph). That is a significant jump from the

  14.9 factor for the stock 8.5:1 compression.”

 

I have difficulty believing 16.6 hr hour per gallon.  Assuming 5.85 pounds per gallon (a GAMI figure)I calculate that this is equivalent to a specific fuel consumption of 0.352 pounds per horsepower hour which is into diesel territory. 

 

I plotted some SFC data published by manufacturers including liquid cooled IOL-200 used on Voyager which had a compression ratio of 11.4.  It suggested that the correct figure for a compression ratio of 10 is closer to 15 hp hr/gallon.    The figure of 14.9 sounds too high for 8.5:1 compression as well.  I would expect it to be about 6% lower efficiency based on charts of efficiency vs compression ratio, or about 14.1 HP hr/gallon at 8.5:1.

 

As usual, carefully collected data collected with calibrated instruments should tell the tale.

 

Fred Moreno

 

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