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Message-ID: <1b4b137c0708240930n11cbcf79qe30468f4c77991b1@mail.gmail.com>
Date: Fri, 24 Aug 2007 12:30:30 -0400
From: "Tracy Crook" <tracy@rotaryaviation.com>
Sender: rwstracy@gmail.com
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Carb
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I think this is the spec on ventury vacuum (V V) at max specified CFM.
Performance carbs (generally 4 barrels) are designed with about 1/2 the
ventury drop as "grocery getter" carb designs.  The less the V V, the better
WOT performance (more MAP) but the harder it is to design due to the smaller
signal.  10" H2O is a pretty small signal for MAX CFM.

BTW, This is unrelated to throat size.

Tracy Crook


On 8/23/07, George Lendich <lendich@optusnet.com.au> wrote:
>
>  Ed, Lynn, Bill or anyone.
> I'm trying to figure out how to extrapolate various air flow figures which
> have different vacuum testing parameters such as those with 10" of water
> verses those with 12" of water and 20.4" of water. I don't know where the
> 20.4" of water comes from, but apparently it does exist.
> I assume there is some calculation which can be applied?
> I'm only concerned with extrapolating from one ( known value like 10") to
> another ( like 12") - for comparison purposes.
> George ( down under)
>

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<div>I think this is the spec on ventury vacuum (V V) at max specified CFM.&nbsp; Performance carbs (generally 4 barrels) are designed with about 1/2 the ventury drop as &quot;grocery getter&quot; carb designs.&nbsp; The less the V V, the better WOT performance (more MAP) but the harder it is to design&nbsp;due to the smaller signal.&nbsp; 10&quot; H2O is a pretty small signal for MAX CFM.
</div>
<div>&nbsp;</div>
<div>BTW, This is unrelated to throat size.</div>
<div>&nbsp;</div>
<div>Tracy Crook<br><br>&nbsp;</div>
<div><span class="gmail_quote">On 8/23/07, <b class="gmail_sendername">George Lendich</b> &lt;<a href="mailto:lendich@optusnet.com.au">lendich@optusnet.com.au</a>&gt; wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<div bgcolor="#ffffff">
<div><font face="Arial" size="2">Ed, Lynn, Bill or anyone.</font></div>
<div><font face="Arial" size="2">I&#39;m trying to figure out how to extrapolate various air flow figures which have different vacuum testing parameters such as those with 10&quot; of water verses those with 12&quot; of water and 
20.4&quot; of water. I don&#39;t know where the 20.4&quot; of water comes from, but apparently it does exist.</font></div>
<div><font face="Arial" size="2">I assume there is some calculation which can be applied?</font></div>
<div><font face="Arial" size="2">I&#39;m only concerned with extrapolating from one ( known value like 10&quot;)&nbsp;to another ( like 12&quot;) - for comparison purposes.</font></div>
<div><font face="Arial" size="2">George ( down under)</font></div></div></blockquote></div><br>

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