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Date: Tue, 08 Jun 2010 10:41:27 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: high/low pressure pumps question
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Ed Anderson wrote:
>
> Just the opposite, George. Higher fuel pressure raises the temperature =

> (amount of heat) required to turn the fuel into vapor. So higher fuel=20
> pressures tend to lower the likely hood of vapor lock =96 however, if=20
> you raise the fuel temperature high enough, you can probably turn it=20
> into vapor regardless of the pressure. So higher fuel pressure tends=20
> to reduce the likelihood of vapor lock but can not absolutely prevent=20
> it =96 expose your fuel to sufficient heat and you can probably achieve=
=20
> vapor lock at any pressure.
>
> The newer returnless systems monitor the temperature of the fuel as=20
> well as the pressure. I would presume (but don=92t know for certain)=20
> that sensing higher fuel temps would cause the control system to=20
> increase the pressure. It may be that the basic pressure (around 42=20
> psi) is sufficient to control vapor lock under the anticipated=20
> operating temperatures. I would have to figure out what it would take=20
> to heat fuel to its vapor point at 42 psi.
>
According to the link below, if you're vaporizing the fuel at 42psi,=20
you're engine is probably on fire anyway.

http://www.eng-tips.com/viewthread.cfm?qid=3D218716&page=3D4