X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from m12.lax.untd.com ([64.136.30.75] verified) by logan.com (CommuniGate Pro SMTP 4.3.4) with SMTP id 1003483 for flyrotary@lancaironline.net; Wed, 15 Jun 2005 18:10:46 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.136.30.75; envelope-from=alwick@juno.com Received: from m12.lax.untd.com (localhost [127.0.0.1]) by m12.lax.untd.com with SMTP id AABBMBK2UADQVBA2 for (sender ); Wed, 15 Jun 2005 15:09:22 -0700 (PDT) X-UNTD-OriginStamp: L941HVjjYzDhN3itp//mkK17fJsqGlBfJQvGpFig7MgD6Jv3LEMamA== Received: (from alwick@juno.com) by m12.lax.untd.com (jqueuemail) id KVKPUHSC; Wed, 15 Jun 2005 15:09:18 PDT To: flyrotary@lancaironline.net Date: Wed, 15 Jun 2005 15:08:08 -0700 Subject: Re: [FlyRotary] EFI Bleeder Circuit (Was Engine Not Starting) Message-ID: <20050615.150840.3328.3.alwick@juno.com> X-Mailer: Juno 5.0.33 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary=--__JNP_000_6cc9.7c38.3875 X-Juno-Line-Breaks: 8-6,14-23,25-27,31,36-40,42,45-50,52-58,60-136,137-32767 From: al p wick X-ContentStamp: 29:14:3417789933 X-MAIL-INFO:25c3738b736ac7f36a8b0bea8b1eae5f873a9afaa32a97b7fa3a8aaf8af37a97cb8a5f4747030a23032f2343028f8ffb8a1e5ba34ff30bceeeee6e0feb8e9be7276737fee72f03037efe6fa70ebf3e1b3e833fdada63df9a4afa3acb5b63b75bc34e132aaf5b773b5a87df77af2a771e77abd38e9f7edabe635e63f7df1ac3b3731afa9a6b8ebb37de4f4a5f6b2b8e0ff317ee9eea076be7d7b30feb830a0a2702ae6fefebebbfa74f5bce7b02e3434efb0afb876a3e2f2ebf2ba73f5a5a9bbacfe37333832a X-UNTD-Peer-Info: 127.0.0.1|localhost|m12.lax.untd.com|alwick@juno.com This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ----__JNP_000_6cc9.7c38.3875 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit I threw this together, it includes some assumptions, but I think it's pretty close to reality. I strongly suspect that the Egg fuel bleed system actually drops the outlet pressure enough that the pump is able to move the small bubble of air at the pump inlet. If you have a well designed system, that air is displaced automatically and there is no value to the bleed system. I tested my plane and it definitely self primes. The Egg crash plane would not pump fuel hours after the vapor lock. It was not a self priming fuel design. Back to lurking, this my quota of posts for week. ;-) -al wick Subject: Fuel system validation….self priming pump. Scope: This procedure is utilized to determine if your fuel system is able to self prime. It applies to EFI high pressure fuel systems. General: Self priming fuel systems are lower risk that those that don't. These systems have the ability to resume pumping immediately after a flow interruption. Such as when the pilot runs one tank dry, or if there is vapor lock. All systems that allow the fuel pump inlet to get wet after a flow interruption are self priming. This condition is vital on high pressure fuel systems, as the pumps are unable to displace air due to the high pressure on the outlet side of the pump. Only when the inlet is wet are the pumps able to resume flow. Procedure: Drain all fuel from your tank. Verify your engine fuel pressure is at normal pressure, this is typically 36 psi for EFI systems. Activate fuel pump for a few moments to purge fuel from the fuel inlet. You should hear a rattling sound when inlet is purged of fuel. Use care, running pump dry too long can damage pump. Add fuel to tank. Activate fuel pump for a few moments until normal pressure is achieved. Conclusion: If unable to achieve full pressure in 10 seconds, you have failed the test. Modify your fuel system to self wet the fuel inlet. On Wed, 15 Jun 2005 09:13:12 -0500 "Mark R Steitle" writes: > Jofar, > The real purpose of the bleed circuit is to allow the pump to > reprime > itself. Once that happens, the pump builds up pressure again, and > forces all the remaining air out through the pressure regulator. > With a > 5-gal tank sitting on the floor, my system (running one pump) can > reprime itself in about 10 seconds. Yes, under the right > circumstances, > that could be the longest 10 seconds of my life. This should only > happen if you run a tank dry. But if that happens, the procedure > will > be to switch to the other tank (should have fuel), then turn on the > boost pump. That should reduce the recovery time to something less > than > 10 seconds. > > Mark > > -----Original Message----- > From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] > On > Behalf Of jesse farr > Sent: Wednesday, June 15, 2005 8:47 AM > To: Rotary motors in aircraft > Subject: [FlyRotary] Re: Engine Not Starting > > I don't know nothing (actually pretty much anything) about any of > this > but > that has never stopped me from having and voicing an opinion; so, if > > injectors only fire small percentage of time and fuel & compressed > air > flow > not sufficient at times to clear out in time to get started while > flying > ac, > bleed return definitly sounds like good idea. But, if sufficiently > far > away > from injectors, then even though now have flow established to the > bleed > point, you will still have slow go to purge remaining compressed > air, > vapor > and allow fuel to actually flow from there to injectors and inject. > It > may > just take a few seconds longer but that is still a tight a-- time > of > flying, > starting, praying, cursing own stupidity, etc.. Could I suggest > might be > > better to put bleed point at end of fuel rail so as to pass vapor > all > the > way more quickly ? After all, small orfice and line return to tank > shouldn't > create that much more of a problem. Is there some other problem > there > that I > simply do not know enough to understand ? > jofarr, soddy tn > > >> Homepage: http://www.flyrotary.com/ > >> Archive: http://lancaironline.net/lists/flyrotary/List.html > > -al wick Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5 N9032U 200+ hours on engine/airframe from Portland, Oregon Prop construct, Subaru install, Risk assessment, Glass panel design info: http://www.maddyhome.com/canardpages/pages/alwick/index.html ----__JNP_000_6cc9.7c38.3875 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: quoted-printable

I threw this together, = it=20 includes some assumptions, but I think it's pretty close to reality. I = strongly=20 suspect that the Egg fuel bleed system actually drops the outlet pressure = enough=20 that the pump is able to move the small bubble of air at the pump inlet. If= you=20 have a well designed system, that air is displaced automatically and there = is no=20 value to the bleed system. I tested my plane and it definitely self primes.= The=20 Egg crash plane would not pump fuel hours after the vapor lock. It was not = a=20 self priming fuel design.

Back to lurking, this my= quota of=20 posts for week. ;-)

 

-al wick

 

 

Subject:

Fuel system validation&#= 8230;.self=20 priming pump.

 

Scope:

This procedure is = utilized to=20 determine if your fuel system is able to self prime. It applies to EFI high= =20 pressure fuel systems.

 

General:

Self priming fuel = systems are=20 lower risk that those that don't. These systems have the ability to resume= =20 pumping  immediately after a = flow=20 interruption. Such as when the pilot runs one tank dry, or if there is = vapor=20 lock.

All systems that allow = the fuel=20 pump inlet to get wet after a flow interruption are self priming. This = condition=20 is vital on high pressure fuel systems, as the pumps are unable to displace= air=20 due to the high pressure on the outlet side of the pump. Only when the = inlet is=20 wet are the pumps able to resume flow.

 

Procedure:

 

Drain all fuel from your= =20 tank.

Verify your engine fuel = pressure=20 is at normal pressure, this is typically 36 psi for EFI systems.

Activate fuel pump for a= few=20 moments to purge fuel from the fuel inlet. You should hear a rattling sound= when=20 inlet is purged of fuel. Use care, running pump dry too long can damage=20 pump.

Add fuel to tank.

Activate fuel pump for a= few=20 moments until normal pressure is achieved.

 

Conclusion:

 

If unable to achieve = full=20 pressure in 10 seconds, you have failed the test. Modify your fuel system = to=20 self wet the fuel inlet.

 

 

 

 

 

 

On Wed, 15 Jun 2005 09:13:12 -0500 "Mark R Steitle" <mark.steitle@austin.utexas.= edu>=20 writes:
> Jofar,
> The real purpose of the bleed circuit is to = allow=20 the pump to
> reprime
> itself.  Once that happens, the = pump=20 builds up pressure again, and
> forces all the remaining air out = through=20 the pressure regulator. 
> With a
> 5-gal tank sitting on= the=20 floor, my system (running one pump) can
> reprime itself in about 10= =20 seconds.  Yes, under the right
> circumstances,
> that = could=20 be the longest 10 seconds of my life.  This should only
> happen= if=20 you run a tank dry.  But if that happens, the procedure
>=20 will
> be to switch to the other tank (should have fuel), then turn = on=20 the
> boost pump.  That should reduce the recovery time to = something=20 less
> than
> 10 seconds.
>
> Mark
>
&= gt;=20 -----Original Message-----
> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.= net]=20
> On
> Behalf Of jesse farr
> Sent: Wednesday, June 15, = 2005=20 8:47 AM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] = Re:=20 Engine Not Starting
>
> I don't know nothing (actually pretty = much=20 anything) about any of
> this
> but
> that has never = stopped=20 me from having and voicing an opinion; so, if
>
> injectors = only=20 fire small percentage of time and fuel & compressed
> air
>= ;=20 flow
> not sufficient at times to clear out in time to get started = while=20
> flying
> ac,
> bleed return definitly sounds like = good=20 idea. But, if sufficiently
> far
> away
> from = injectors,=20 then even though now have flow established to the
> bleed
> = point,=20 you will still have slow go to purge remaining compressed
> air,
= >=20 vapor
> and allow fuel to actually flow from there to injectors and= =20 inject.
> It
> may
> just take a few seconds longer but= that=20 is still a tight a-- time
> of
> flying,
> starting,=20 praying, cursing own stupidity, etc.. Could I suggest
> might be
= >=20
> better to put bleed point at end of fuel rail so as to pass vapor= =20
> all
> the
> way more quickly ? After all, small = orfice and=20 line return to tank
> shouldn't
> create that much more of a=20 problem. Is there some other problem
> there
> that I
>= =20 simply do not know enough to understand ?
> jofarr, soddy tn
>= =20
> >>  Homepage:  http://www.flyrotary.com/
>=20 >>  Archive:   http://= lancaironline.net/lists/flyrotary/List.html
>=20
>
 
 
-al wick
Artificial intelligence in cockpit, Cozy IV powered by = stock=20 Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, OregonProp=20 construct, Subaru install, Risk assessment, Glass panel design info:
http:= //www.maddyhome.com/canardpages/pages/alwick/index.html
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