X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-bk0-f52.google.com ([209.85.214.52] verified) by logan.com (CommuniGate Pro SMTP 5.4.5) with ESMTPS id 5598323 for flyrotary@lancaironline.net; Wed, 13 Jun 2012 20:24:42 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.214.52; envelope-from=msteitle@gmail.com Received: by bkcjc3 with SMTP id jc3so890365bkc.25 for ; Wed, 13 Jun 2012 17:24:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=vipIicX04b/IJv14ympTFLba5HXp4GaSTau/1uZX3/Y=; b=j8LrwiysvV1CDxBhQutdyFO54gajrfH690FhmwhNpu8Aak5k/n8fkoES21oWXI7Q/7 rYuZBVg93CxBjG0DarpB0IPBzkX4HApwo48flQz4E81i47d3JGwpVNuNvCQ358JSbWoY 99ISJj8xc9qlTg4++N7q65uwnrkC0QgAUj4TQYH4TOGMCOW4l1IORXIUSF7Zr4fb0jxn 6WzH+0bOn4m7Uj9P7ZA/azaXwcT3NiMHTK009zzmg7xALHgtyuhyA1GZ2KhR0hpBAmcN vCoRbRwsmdUB6IqYTzqMtPyKRd92t+UTeTnTHOhMLxtUv6WTahH/zZ46ETSOXAZ8he/I 4sLQ== MIME-Version: 1.0 Received: by 10.205.116.203 with SMTP id fj11mr14490864bkc.108.1339633445089; Wed, 13 Jun 2012 17:24:05 -0700 (PDT) Received: by 10.204.97.194 with HTTP; Wed, 13 Jun 2012 17:24:05 -0700 (PDT) In-Reply-To: References: Date: Wed, 13 Jun 2012 19:24:05 -0500 Message-ID: Subject: Re: [FlyRotary] Two possible causes was : [FlyRotary] Re: Fuel presure question. From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=14dae947310b9fb0ac04c263b703 --14dae947310b9fb0ac04c263b703 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable David, Ed covered what I was thinking about a possible bad check-valve in one of your pumps. And a bunch of other stuff I hadn't considered. Mark On Wed, Jun 13, 2012 at 6:17 PM, Ed Anderson wro= te: > ** > 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 pum= p > 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 a= re > 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 i= s > 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=92s 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. > > 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 the= re > 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 sid= e > increase. > > Another possible cause might be if both of your pumps are fed off the sam= e > electrical line and there is sufficient resistance that when both pumps a= re > 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 > *Sent:* Wednesday, June 13, 2012 6:43 PM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: Fuel presure question. > > Fuel is gravity routed from tanks to ganged fuel selector out to T-fittin= g > 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 pump= s > 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 fr= om > either pump, but both together pressure drops. David > > ------------------------------ > *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 > --14dae947310b9fb0ac04c263b703 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable David,=A0

Ed covered what I was thinking about a possibl= e bad check-valve in one of your pumps. =A0And a bunch of other stuff I had= n't considered.

Mark=A0

On Wed, Jun 13, 2012 at 6:17 PM, Ed Anderson <eanderson@carolina.= rr.com> wrote:
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.=A0 So if one pump is off and the other on, the on pump does n= ot=20 pump fuel backwards through the off pump.=A0 Since each pump produces the 4= 2=20 psi pressure by itself, one would assume the pumping elements in both pumps= are=20 working properly.=A0 Also assuming the pressure change is NOT due to a=20 malfunctioning pressure sensor.
=A0
Here are some things that you might want to=20 consider:
=A0
1.=A0 That somehow when both pumps are on - one o= f the=20 pumps check valves is not closing properly.=A0 Not a=A0 pump expert so not= =20 certain this could even happen - but the thought occurred to me.
=A0
2.=A0 The effect of Increased fuel flow rate due = to=20 both pumps=A0may be=A0causing a pressure drop through an upstream orifice= =20 (like perhaps your "T").
=A0
3.=A0 Turning on both pumps (assuming on the same= =20 circuit) might cause sufficient voltage drop in the line sufficient to decr= ease=20 the pumping performance of both pumps - pump flow rates are sensitive to vo= ltage=20 variations.
=A0
4.=A0 The pressure return regulator might be=20 malfunctioning and opening due to the higher flow rate - easy to check, jus= t=20 temporarily block off the return.=A0 If the symptom disappears then it=92s = the=20 regulator.
=A0
=A0
Theoretically, if the fuel flow rate through the = T's and=20 pumps=A0 does not change with both pumps on, then the pressure should remai= n=20 the same=A0 - which is what you are expecting, but not seeing.=A0=20
=A0
So since the pressure does change (drops) - what = could=20 cause this (assuming the pressure drop is real and not the result some stra= nge=20 malfunction of your gauge)?
=A0
=A0 One thing that could cause it, is if the fuel= flow=20 rate increases through an upstream orifice=A0in your fuel line (say at the= =20 "T" which=A0feeds your two pumps) =A0then the pressure on the oth= er=20 (downstream) side will drop.=A0 Turn one of the pumps off, the fuel flow ra= te=20 drops, therefore there is less pressure drop across this orifice =A0and you= r=20 fuel pressure on the downstream side of the orifice will again go=20 up.
=A0
Its similar to a resistor in a circuit.=A0 The re= sistor=20 value will remain static - the same, but if you pull more current thought i= t,=20 the voltage drop across it will increase resulting in less voltage on the= =20 downstream side.=A0 Reduce the current flow back to previous rate=A0and=20 the voltage drop across the resistor decreases and therefore voltage on the= =20 downstream side increase.
=A0
Another possible cause might be if both of your p= umps are=20 fed off the same electrical line and there is sufficient resistance that wh= en=20 both pumps are on the voltage drop causes less performance by both=20 pumps.
=A0
Just=A0some WAGs that you might consider, if the= =20 suggestions make by others do not result in identifying the cause.
=A0
Good Luck
=A0
Ed
=A0
Edward L. Anderson
Anderson Electronic Enterpr= ises=20 LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com

Sent: Wednesday, June 13, 2012 6:43 PM
Subject: [FlyRotary] Re: Fuel presure question.

Fuel is gravity=20 routed from tanks to ganged fuel selector out to T-fitting with each pump o= n the=20 sides of the T,=A0 to another T,=A0 into main line out to eng.,=20 pressure=A0sender is mounted directly after the T=A0 where the two pumps=20 come together.=A0=A0 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.=A0=A0=20 David=A0

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 par= allel=20 or series? =A0What 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... =A0Mine goes up about a pound when I switch on the= =20 second pump. =A0What
> 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 4= 2 PSI=20 on EM2, if I switch on the back-up pump with the
>> primary pump t= he=20 pressure drops to 35 PSI, can here both pumps running, if
>> I swi= tch=20 off either pump pressure goes back to 42 PSI. =A0My 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 cha= mber.=20 =A0Thanks, =A0David
>> R. Cook =A0RV6A=20 Rotary.
>

--
Homepage:=20 =A0http://www.flyro= tary.com/
Archive and UnSub: =A0=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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