X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.4.5) with ESMTP id 5598233 for flyrotary@lancaironline.net; Wed, 13 Jun 2012 19:18:09 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=2.0 cv=U/AQ/JXu c=1 sm=0 a=g3L/TDsr+eNLfIieSKfGkw==:17 a=AHkS0RJitIMA:10 a=NcIODMwr8F0A:10 a=05ChyHeVI94A:10 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=r1ClD_H3AAAA:8 a=C_IRinGWAAAA:8 a=pGLkceISAAAA:8 a=Ia-xEzejAAAA:8 a=7g1VtSJxAAAA:8 a=oCcaPWc0AAAA:8 a=_y3vZxEqYiw_kphS-LcA:9 a=QEXdDO2ut3YA:10 a=Qa1je4BO31QA:10 a=si9q_4b84H0A:10 a=MSl-tDqOz04A:10 a=EzXvWhQp4_cA:10 a=dIBGocxz_zbC0Y9JQIoA:9 a=_W_S_7VecoQA:10 a=g3L/TDsr+eNLfIieSKfGkw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.170.10 Received: from [174.110.170.10] ([174.110.170.10:50749] helo=EdPC) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 35/AC-07841-D8F19DF4; Wed, 13 Jun 2012 23:17:33 +0000 Message-ID: <7EFC92271AC241D4B182F11F2E937A82@EdPC> From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Two possible causes was : [FlyRotary] Re: Fuel presure question. Date: Wed, 13 Jun 2012 19:17:33 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00DB_01CD4999.2F82FD30" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_00DB_01CD4999.2F82FD30 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable David, don't know whether you have considered this - as you are aware = the two pumps are able to work in parallel because the pumps have check = valves. So if one pump is off and the other on, the on pump does not = pump fuel backwards through the off pump. Since each pump produces the = 42 psi pressure by itself, one would assume the pumping elements in both = pumps are working properly. Also assuming the pressure change is NOT = due to a malfunctioning pressure sensor. Here are some things that you might want to consider: 1. That somehow when both pumps are on - one of the pumps check valves = is not closing properly. Not a pump expert so not certain this could = even happen - but the thought occurred to me. 2. The effect of Increased fuel flow rate due to both pumps may be = causing a pressure drop through an upstream orifice (like perhaps your = "T"). 3. Turning on both pumps (assuming on the same circuit) might cause = sufficient voltage drop in the line sufficient to decrease the pumping = performance of both pumps - pump flow rates are sensitive to voltage = variations. 4. The pressure return regulator might be malfunctioning and opening = due to the higher flow rate - easy to check, just temporarily block off = the return. If the symptom disappears then it=E2=80=99s the regulator. Theoretically, if the fuel flow rate through the T's and pumps does not = change with both pumps on, then the pressure should remain the same - = which is what you are expecting, but not seeing. =20 So since the pressure does change (drops) - what could cause this = (assuming the pressure drop is real and not the result some strange = malfunction of your gauge)? One thing that could cause it, is if the fuel flow rate increases = through an upstream orifice in your fuel line (say at the "T" which = feeds your two pumps) then the pressure on the other (downstream) side = will drop. Turn one of the pumps off, the fuel flow rate drops, = therefore there is less pressure drop across this orifice and your fuel = pressure on the downstream side of the orifice will again go up. Its similar to a resistor in a circuit. The resistor value will remain = static - the same, but if you pull more current thought it, the voltage = drop across it will increase resulting in less voltage on the downstream = side. Reduce the current flow back to previous rate and the voltage = drop across the resistor decreases and therefore voltage on the = downstream side increase. Another possible cause might be if both of your pumps are fed off the = same electrical line and there is sufficient resistance that when both = pumps are on the voltage drop causes less performance by both pumps. Just some WAGs that you might consider, if the suggestions make by = others do not result in identifying the cause. Good Luck Ed Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com From: hoursaway1@comcast.net=20 Sent: Wednesday, June 13, 2012 6:43 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: Fuel presure question. Fuel is gravity routed from tanks to ganged fuel selector out to = T-fitting with each pump on the sides of the T, to another T, into = main line out to eng., pressure sender is mounted directly after the T = where the two pumps come together. All this is in front of the wing = spar near the floor in an RV6A. This would make the pumps in parallel & = the pressure is the same from either pump, but both together pressure = drops. David=20 -------------------------------------------------------------------------= ------- From: "Mark Steitle" msteitle@gmail.com To: "Rotary motors in aircraft" Sent: Wednesday, June 13, 2012 8:36:19 AM Subject: [FlyRotary] Re: Fuel presure question. David, How are your pumps plumbed... in parallel or series? What kind of pressure do you get when running the backup pump only? Mark On 6/13/12, Tracy wrote: > Hmmmm... Mine goes up about a pound when I switch on the second pump. = What > happens when you turn both off? > > Tracy > > Sent from my iPad > > On Jun 12, 2012, at 7:11 PM, hoursaway1@comcast.net wrote: > >> Question about fuel pressure indications, at fast idle 2200 RPM, fuel >> pressure is 42 PSI on EM2, if I switch on the back-up pump with the >> primary pump the pressure drops to 35 PSI, can here both pumps = running, if >> I switch off either pump pressure goes back to 42 PSI. My system is = 13B, >> stock red injectors all four, pressure regulator is stock Mazda on = the end >> of fuel rail with vacume connection from dynamic chamber. Thanks, = David >> R. Cook RV6A Rotary. > -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2180 / Virus Database: 2433/5068 - Release Date: = 06/13/12 ------=_NextPart_000_00DB_01CD4999.2F82FD30 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
David, don't know whether you have considered = this - as=20 you are aware the two pumps are able to work in parallel because the = pumps have=20 check valves.  So if one pump is off and the other on, the on pump = does not=20 pump fuel backwards through the off pump.  Since each pump produces = the 42=20 psi pressure by itself, one would assume the pumping elements in both = pumps are=20 working properly.  Also assuming the pressure change is NOT due to = a=20 malfunctioning pressure sensor.
 
Here are some things that you might want to=20 consider:
 
1.  That somehow when both pumps are on - = one of the=20 pumps check valves is not closing properly.  Not a  pump = expert so not=20 certain this could even happen - but the thought occurred to = me.
 
2.  The effect of Increased fuel flow rate = due to=20 both pumps may be causing a pressure drop through an upstream = orifice=20 (like perhaps your "T").
 
3.  Turning on both pumps (assuming on the = same=20 circuit) might cause sufficient voltage drop in the line sufficient to = decrease=20 the pumping performance of both pumps - pump flow rates are sensitive to = voltage=20 variations.
 
4.  The pressure return regulator might be=20 malfunctioning and opening due to the higher flow rate - easy to check, = just=20 temporarily block off the return.  If the symptom disappears then = it=E2=80=99s the=20 regulator.
 
 
Theoretically, if the fuel flow rate through the = T's and=20 pumps  does not change with both pumps on, then the pressure should = remain=20 the same  - which is what you are expecting, but not seeing. =20
 
So since the pressure does change (drops) - what = could=20 cause this (assuming the pressure drop is real and not the result some = strange=20 malfunction of your gauge)?
 
  One thing that could cause it, is if the = fuel flow=20 rate increases through an upstream orifice in your fuel line (say = at the=20 "T" which feeds your two pumps)  then the pressure on the = other=20 (downstream) side will drop.  Turn one of the pumps off, the fuel = flow rate=20 drops, therefore there is less pressure drop across this orifice =  and your=20 fuel pressure on the downstream side of the orifice will again go=20 up.
 
Its similar to a resistor in a circuit.  = The resistor=20 value will remain static - the same, but if you pull more current = thought it,=20 the voltage drop across it will increase resulting in less voltage on = the=20 downstream side.  Reduce the current flow back to previous = rate and=20 the voltage drop across the resistor decreases and therefore voltage on = the=20 downstream side increase.
 
Another possible cause might be if both of your = pumps are=20 fed off the same electrical line and there is sufficient resistance that = when=20 both pumps are on the voltage drop causes less performance by both=20 pumps.
 
Just some WAGs that you might consider, if = the=20 suggestions make by others do not result in identifying the = cause.
 
Good Luck
 
Ed
 
Edward L. Anderson
Anderson Electronic = Enterprises=20 LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com

From: hoursaway1@comcast.net
Sent: Wednesday, June 13, 2012 6:43 PM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: Fuel presure = question.

Fuel = is gravity=20 routed from tanks to ganged fuel selector out to T-fitting with each = pump on the=20 sides of the T,  to another T,  into main line out to eng.,=20 pressure sender is mounted directly after the T  where the two = pumps=20 come together.   All this is in front of the wing spar near = the floor=20 in an RV6A. This would make the pumps in parallel & the pressure is = the same=20 from either pump, but both together pressure drops.  =20 David 

From: "Mark Steitle" msteitle@gmail.com
To: = "Rotary=20 motors in aircraft" <flyrotary@lancaironline.net>
Sent:=20 Wednesday, June 13, 2012 8:36:19 AM
Subject: [FlyRotary] = Re: Fuel=20 presure question.

David,

How are your pumps plumbed... in = parallel=20 or series?  What kind of
pressure do you get when running the = backup=20 pump only?

Mark

On 6/13/12, Tracy = <rwstracy@gmail.com>=20 wrote:
> Hmmmm...  Mine goes up about a pound when I switch = on the=20 second pump.  What
> happens when you turn both = off?
>
>=20 Tracy
>
> Sent from my iPad
>
> On Jun 12, 2012, = at 7:11=20 PM, hoursaway1@comcast.net wrote:
>
>> Question about = fuel=20 pressure indications, at fast idle 2200 RPM, fuel
>> pressure = is 42 PSI=20 on EM2, if I switch on the back-up pump with the
>> primary = pump the=20 pressure drops to 35 PSI, can here both pumps running, if
>> I = switch=20 off either pump pressure goes back to 42 PSI.  My system is=20 13B,
>> stock red injectors all four, pressure regulator is = stock Mazda=20 on the end
>> of fuel rail with vacume connection from dynamic = chamber.=20  Thanks,  David
>> R. Cook  RV6A=20 Rotary.
>

--
Homepage:=20  http://www.flyrotary.com/
Archive and UnSub:  =20 http://mail.lancaironline.net:81/lists/flyrotary/List.html

No virus found in this=20 message.
Checked by AVG - www.avg.com
Version: 2012.0.2180 / = Virus=20 Database: 2433/5068 - Release Date: 06/13/12

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