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Date: Tue, 25 Aug 2009 15:49:09 -0400
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From: Gary Casey <casey.gary@yahoo.com>
Subject: Re: Plenum pressure and Injector performance LOP
In-Reply-To: <list-3823680@logan.com>
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The vent on each injector is there to normalize the pressure drop across th=
e injector and to improve the atomization.=A0 If the engine air inlet is ve=
ry efficient the pressure in the manifold may be close or maybe even higher=
 than the pressure around the injector, reversing the direction of air flow=
 through the vents.=A0 This is the case if the pressure recovery in the eng=
ine inlet is more than the pressure recovery of the cooling air.=A0 Then fu=
el will either be poorly atomized or can actually be blown out the injector=
 through the vents.=A0 Some people have seen fuel stains around the injecto=
r, proof that this is happening.=A0 The poor atomization can cause irregula=
r fuel flow into the engine, creating a rough condition.=A0 Some people hav=
e used the "turbo" shrouds around the injectors to source the bleed air to =
a higher pressure source, presumably the engine air inlet ahead of the filt=
er.=A0 This gives the best possible chance at sufficient atomization.=A0
 Others have run the vents to a "pitot tube" inlet ahead of the engine air =
cooling inlets.=A0 Regardless, the idea is to get the pressure surrounding =
the injectors as high as possible.=A0 Once I was thinking of ducting the va=
cuum pump outlet to the=A0injectors - but didn't, as I wasn't sure about th=
e relative air flow.=A0 Within reason you can't get it too high.=0AGary Cas=
ey=0A=0A=0ANote: Forwarded message is attached.=0AHey guys, I am rememberin=
g a long time ago reading about=0Ahow the air pressure surrounding the inje=
ctor can affect how=0Awell the injector works.=A0 If I'm not mistaken, turb=
ocharged=0Aengines even use some pressure manifold around the injector=0Ato=
 accommodate for the increased Manifold Pressure.=0A=0A....=A0 The cowl is =
known to often have too little exit=0Aarea, so it could be that the pressur=
e differential is=0Aeven too high between the top and bottom half of the=0A=
cowl.=0A=0AAny insight you can give?=0AThanks,=0ATim=0A=0A=0A=0A      
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<html><head><style type=3D"text/css"><!-- DIV {margin:0px;} --></style></he=
ad><body><div style=3D"font-family:times new roman, new york, times, serif;=
font-size:12pt"><DIV>The vent on each injector is there to normalize the pr=
essure drop across the injector and to improve the atomization.&nbsp; If th=
e engine air inlet is very efficient the pressure in the manifold may be cl=
ose or maybe even higher than the pressure around the injector, reversing t=
he direction of air flow through the vents.&nbsp; This is the case if the p=
ressure recovery in the engine inlet is more than the pressure recovery of =
the cooling air.&nbsp; Then fuel will either be poorly atomized or can actu=
ally be blown out the injector through the vents.&nbsp; Some people have se=
en fuel stains around the injector, proof that this is happening.&nbsp; The=
 poor atomization can cause irregular fuel flow into the engine, creating a=
 rough condition.&nbsp; Some people have used the "turbo" shrouds around
 the injectors to source the bleed air to a higher pressure source, presuma=
bly the engine air inlet ahead of the filter.&nbsp; This gives the best pos=
sible chance at sufficient atomization.&nbsp; Others have run the vents to =
a "pitot tube" inlet ahead of the engine air cooling inlets.&nbsp; Regardle=
ss, the idea is to get the pressure surrounding the injectors as high as po=
ssible.&nbsp; Once I was thinking of ducting the vacuum pump outlet to the&=
nbsp;injectors - but didn't, as I wasn't sure about the relative air flow.&=
nbsp; Within reason you can't get it too high.<BR>Gary Casey</DIV>=0A<DIV s=
tyle=3D"FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, ser=
if"><BR>=0A<DIV style=3D"FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new=
 york, times, serif">Note: Forwarded message is attached.<BR>Hey guys, I am=
 remembering a long time ago reading about<BR>how the air pressure surround=
ing the injector can affect how<BR>well the injector works.&nbsp; If I'm no=
t mistaken, turbocharged<BR>engines even use some pressure manifold around =
the injector<BR>to accommodate for the increased Manifold Pressure.<BR><BR>=
.....&nbsp; The cowl is known to often have too little exit<BR>area, so it c=
ould be that the pressure differential is<BR>even too high between the top =
and bottom half of the<BR>cowl.<BR><BR>Any insight you can give?<BR>Thanks,=
<BR>Tim<BR></DIV></DIV></div><br>=0A=0A      </body></html>
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