Mark Wrathall wrote:

Hi Paul,

I received the following message from Jim LoPresti. He was responding to this article from Fred on wankel.org.

http://www.wankel.org/72_Engine/72-46%20Cooling_Theory.htm

I replied asking him to join this newsgroup to discuss it, but got a reject from his server, which thought my message was spam.

Mark Wrathall

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I enjoyed your web site; especially your story on Cooling Theory



Engine cooling is my favorite subject.



I like to collect published reports and read about cooling on the web

Along with my applied research over the last 18 years.



Engine cooling is not very well understood. I am always amazed at the proliferation

Of old wife?s tales, miss-conceptions, myths and untruths which make it into print and

Are touted as accepted fact.



You say people make inlets too small and exits too big?.

It is my experience that most inlets have significant total pressure losses and are therefore

Required to have much slower flow to recover the same  pressure as one with low losses (Like my inlets).

Inlets are almost ALWAYS way too big. Lance can have small inlets because he gets half of his pumping

From his suction exit (Double the drag penalty)?So Does a Mooney ovation or Cirrus.



As airflow approaches a cowling it slows down and the static pressure rises BUT the total pressure

 remains the same following Bernoilli?s equation?total pressure remains the same.

Inlets feed off of TOTAL pressure; they care not how it is portioned. There is no advantage to

Outside diffusion.



Because of this you don?t need to put inlets in a region of high static pressure, you want them in a

An area of high TOTAL pressure. (like close to the prop)



I am curious about your notion of stream tube expansion ratios?never heard of this figure before

And it does not make any sense to me. I am familiar with Miley?s cooling work; and I?m VERY familiar

 with Roy LoPresti?s cowl design work. I assure you my father never sized an inlet with

 streamtube expansion ratio?s. Its all about slipstream total pressures and local inlet velocities.

Im curious as to how you got that ratio thing from the work of either of these guys.



You size inlet/exit to minimize the combination of pressure drag and momentum losses

 
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