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Fuel flow transducer

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speckter(at)comcast.net
Guest

Posted: Tue Feb 06, 2007 9:28 am Post subject: Fuel flow transducer

I have installed my flow-scan transducer in the tunnel like Van's said to.

Now OP says it should go between the fuel servo and the spider.  Anyone have

experience with it in the tunnel?  Any problems?  I really don't want to

replumb it unless I need to.



Gary Specketer

40274

Deems Davis

Joined: 09 Jan 2006
Posts: 925

Posted: Tue Feb 06, 2007 9:50 am Post subject: Fuel flow transducer

Gary, When you say 'the fuel servo' what are you referring to? I've 

installed mine in the tunnel in the appropriate Van's designated 

location. I vaguely recall reading something in the JPI sensor 

installation information about it being installed between some 

components, but their installation documentation (from what I can infer) 

assumes that it's being installed as an add on to an existing certified 

aircraft. where the installation usually needs to happen forward of the 

firewall.  Who (at) OP told you this? They have some new people that may be 

good at their particular tasks but not necessarily (at) building an 

airplane. Off the top of my head I can't for the life of me think of why 

leaving it in its present position shouldn't work. The amount of fuel 

that passes through the transducer is the same if placed there vs. 

further forward.



just my $.02 I'd be interested in learning what you find.



Deems Davis # 406

Finishing - ( A Misnomer ! )

http://deemsrv10.com/

gary wrote:

 	  Quote: 	
		   



 I have installed my flow-scan transducer in the tunnel like Van's said to.

 Now OP says it should go between the fuel servo and the spider.  Anyone have

 experience with it in the tunnel?  Any problems?  I really don't want to

 replumb it unless I need to.

rvbuilder(at)sausen.net
Guest

Posted: Tue Feb 06, 2007 10:10 am Post subject: Fuel flow transducer

It's not uncommon for many of the engine monitor vendors to suggest

the location upstream of the fuel pumps and servo.  It is generally

considered more accurate but installs have shown that Van's location is

just as good.  One of the arguments have always been the heat the

transducer would have to endure in the engine compartment but that has

also been shown to not make a difference.  I plan on installing near the

servo.



Michael

-10 #352 Limbo



--

jesse(at)saintaviation.co
Guest

Posted: Tue Feb 06, 2007 10:25 am Post subject: Fuel flow transducer

Seems to work great in the tunnel in my experience.



Do not archive.



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

www.saintaviation.com

Cell: 352-427-0285

Fax: 815-377-3694

--

speckter(at)comcast.net
Guest

Posted: Tue Feb 06, 2007 12:36 pm Post subject: Fuel flow transducer

OP sent me to JPI who responded to me with "follow the manual".  I asked

again if It would work in the tunnel.  No reply yet.

I did misspeak though.  The manual wants it between the engine fuel pump and

the servo if there are no return lines.

Gary

40274



--

Deems Davis

Joined: 09 Jan 2006
Posts: 925

Posted: Tue Feb 06, 2007 3:20 pm Post subject: Fuel flow transducer

JPI is known for not being particularly responsive to experimental 

aircraft. So you may be a while in getting a response. I suppose that by 

putting it between the engine driven fuel pump and the servo, that you 

are measuring the flow a step closer to the actual detonation, and any 

flow restrictions/problems due to the engine driven pump might be 

registered with the sensor in that location. But if the engine is 

supposed to burn 11 gph at a certain altitude and power setting, I cant' 

see where measuring the flow  on the other side of the engine driven 

fuel pump would make a difference. There's only one line that connects 

them, and if the amount of fuel flowing is different on one side of the 

pump or the other, there's got to be a leak in the fuel delivery system.

Deems Davis # 406

Finishing - ( A Misnomer ! )

http://deemsrv10.com/



Trying to fit the James Cowl



gary wrote:

[quote] 



 OP sent me to JPI who responded to me with "follow the manual".  I asked

 again if It would work in the tunnel.  No reply yet.

 I did misspeak though.  The manual wants it between the engine fuel pump and

 the servo if there are no return lines.

 Gary

 40274



 --

apilot2(at)gmail.com
Guest

Posted: Tue Feb 06, 2007 6:29 pm Post subject: Fuel flow transducer

Deems, the standard mechanical diaphram pump can and will develop a

leak eventually. There is a drain that is supposed to be a tell

tale...if you are on the ground. By having the sensor before that

pump, you would measure the engine consumption plus the leak. That

would argue for placing the sensor before the pumps.

On 2/6/07, Deems Davis <deemsdavis(at)cox.net> wrote:

[quote] 

 JPI is known for not being particularly responsive to experimental

 aircraft. So you may be a while in getting a response. I suppose that by

 putting it between the engine driven fuel pump and the servo, that you

 are measuring the flow a step closer to the actual detonation, and any

 flow restrictions/problems due to the engine driven pump might be

 registered with the sensor in that location. But if the engine is

 supposed to burn 11 gph at a certain altitude and power setting, I cant'

 see where measuring the flow  on the other side of the engine driven

 fuel pump would make a difference. There's only one line that connects

 them, and if the amount of fuel flowing is different on one side of the

 pump or the other, there's got to be a leak in the fuel delivery system.

 Deems Davis # 406

 Finishing - ( A Misnomer ! )

 http://deemsrv10.com/

 Trying to fit the James Cowl

 gary wrote:

 > 

 >

 > OP sent me to JPI who responded to me with "follow the manual".  I asked

 > again if It would work in the tunnel.  No reply yet.

 > I did misspeak though.  The manual wants it between the engine fuel pump and

 > the servo if there are no return lines.

 > Gary

 > 40274

 >

 > --

Deems Davis

Joined: 09 Jan 2006
Posts: 925

Posted: Tue Feb 06, 2007 7:58 pm Post subject: Fuel flow transducer

Just for my edumacation, if the diaphragm was ruptured or leaking would 

that result in more, or less, fuel being 'pulled from the line and 

'pushed' to the engine? My guess is that it would be less. Is there a 

siphon function which would draw some amount of fuel from the fuel pump 

even if the diaphragm was ruptured?



Deems Davis # 406

Finishing - ( A Misnomer ! )

http://deemsrv10.com/

Kelly McMullen wrote:

 	  Quote: 	
		   



 Deems, the standard mechanical diaphram pump can and will develop a

 leak eventually. There is a drain that is supposed to be a tell

 tale...if you are on the ground. By having the sensor before that

 pump, you would measure the engine consumption plus the leak. That

 would argue for placing the sensor before the pumps.

wcurtis(at)nerv10.com
Guest

Posted: Wed Feb 07, 2007 10:12 am Post subject: Fuel flow transducer

This has come up a few time and after doing some research it turns out that the absolute *ideal* location from a true flow perspective is between the fuel servo and the distribution.  The second best location in this regard is between the mechanical fuel pump and the fuel servo.  And then the third best location from a flow perspective, is in the tunnel at the plans location.  If that was the only concern then you would go with the ideal location, however *ideal* only offers a few ml more accuracy and places the transducer in a more harsh environment.  So your accuracy may improve by .05 of a gal per hour but your transducer will be subject to earlier failure due to it being in a harsher environment.  I think the flying RV-10s have show that the tunnel location works well.William  #40237http://wcurtis.nerv10.com/  --> RV10-List message posted by: "gary" I have installed my flow-scan transducer in the tunnel like Van's said to.Now OP says it should go between the fuel servo and the spider. Anyone haveexperience with it in the tunnel? Any problems? I really don't want toreplumb it unless I need to.Gary Specketer40274    [quote][b]

John Ackerman

Joined: 19 Jun 2006
Posts: 130
Location: Prescott, AZ

Posted: Wed Feb 07, 2007 12:38 pm Post subject: Fuel flow transducer

William, why are the downstream locations more "ideal" than those farther upstream? if the system is leak free, the flow is the same. The fluid is incompressible, so pressure has no effect. What's different? Turbulence? Nah... Temperature - don't think so, but maybe? if so, which location is hotter? more variable?



There's an issue of measuring fuel that is recycled to the tanks, but for most of our Lycoming installations (Subies, etc excepted), recycle is zero, except during purge. Is that what the location preference is about?



Someone here pointed out that an upstream transducer will measure leaks as well as fuel consumed by the engine. That raises the question of whether you're more interested in fuel remaining (fuel flow out of the tanks) or fuel consumption by the engine. Hmmm. 



I (and most of us, I'll bet) would really be grateful for any physical explanations adn rationales you've turned up in your researches.



Thanks!



John Ackerman

On Feb 7, 2007, at 11:14 AM, William Curtis wrote:

[quote]This has come up a few time and after doing some research it turns out that the absolute *ideal* location from a true flow perspective is between the fuel servo and the distribution.  The second best location in this regard is between the mechanical fuel pump and the fuel servo.  And then the third best location from a flow perspective, is in the tunnel at the plans location.  If that was the only concern then you would go with the ideal location, however *ideal* only offers a few ml more accuracy and places the transducer in a more harsh environment.  So your accuracy may improve by .05 of a gal per hour but your transducer will be subject to earlier failure due to it being in a harsher environment.  I think the flying RV-10s have show that the tunnel location works well.



William  #40237

http://wcurtis.nerv10.com/



  --> RV10-List message posted by: "gary" 



I have installed my flow-scan transducer in the tunnel like Van's said to.

Now OP says it should go between the fuel servo and the spider. Anyone have

experience with it in the tunnel? Any problems? I really don't want to

replumb it unless I need to.



Gary Specketer

40274

  	  Quote: 	
		  

href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List

href="http://forums.matronics.com">http://forums.matronics.com



	
[b]

mike(at)learningplanet.co
Guest

Posted: Wed Feb 07, 2007 1:55 pm Post subject: Fuel flow transducer

I faced the same dilemma when installing the transducer on the -9A. The problem with the 2-place RVs is that there really is no good place aft of the firewall to install the transducer. There is no tunnel after all. 

What I (and others) have done is to place it forward of the firewall between the gascolator and the carburetor. Obviously this would be a bit different for a fuel injected engine. On my installation I had only about 5" of straight tubing where it enters the transducer, which is less than optimal.



Operationally the transducer is very accurate unless I have the boost pump on. The boost pump must introduce some pulses into the fuel line and the little turbine in the transducer apparently doesn't like it. The result is that when the boost pump is running it reports about 4gph higher than it does normally.



Regards,

Mike Schipper

RV-9A - N63MS - Flying - www.my9a.com

RV-10 - #40576 - Wings - www.rvten.com

On Feb 7, 2007, at 2:37 PM, John Ackerman wrote:

 	  Quote: 	
		  William, why are the downstream locations more "ideal" than those farther upstream? if the system is leak free, the flow is the same. The fluid is incompressible, so pressure has no effect. What's different? Turbulence? Nah... Temperature - don't think so, but maybe? if so, which location is hotter? more variable?



There's an issue of measuring fuel that is recycled to the tanks, but for most of our Lycoming installations (Subies, etc excepted), recycle is zero, except during purge. Is that what the location preference is about?



Someone here pointed out that an upstream transducer will measure leaks as well as fuel consumed by the engine. That raises the question of whether you're more interested in fuel remaining (fuel flow out of the tanks) or fuel consumption by the engine. Hmmm. 



I (and most of us, I'll bet) would really be grateful for any physical explanations adn rationales you've turned up in your researches.



Thanks!



John Ackerman

	


 [quote][b]

wcurtis(at)nerv10.com
Guest

Posted: Wed Feb 07, 2007 5:27 pm Post subject: Fuel flow transducer

John,<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />The short answer to you first question is that the further you go “downstream” the less return or alternate paths where fuel can be returned or be dumped overboard.  That being said, your fourth paragraph hits the nail on the head.  As with many things, *ideal* depends on your perspective.  If you want to know how much fuel has flowed out of the tanks, then the tunnel is the best location.  If you want to know how much fuel is actually being consumed by the engine, then a location AFTER the mechanical fuel pump is best.  So you must decide, what do you want your flow indicator to tell you primarily; how much is flowing out of the tanks or how much is getting to the engine?  Under normal circumstances, the two are almost identical; however under certain circumstances more fuel may be flowing out of the tanks (via the main line) than is flowing to the engine.  This may occur due to leaks, faulty mechanical fuel pump, etc.Williamhttp://wcurtis.nerv10.com/  From: John Ackerman johnag5b(at)cableone.net (johnag5b(at)cableone.net)William, why are the downstream locations more "ideal" than those farther upstream?   if the system is leak free, the flow is the same. The fluid is incompressible, so pressure has no effect. What's different? Turbulence? Nah... Temperature - don't think so, but maybe? if so, which location is hotter? more variable?

 

 There's an issue of measuring fuel that is recycled to the tanks, but for most of our Lycoming installations (Subies, etc excepted), recycle is zero, except during purge. Is that what the location preference is about?

 

  Someone here pointed out that an upstream transducer will measure leaks as well as fuel consumed by the engine. That raises the question of whether you're more interested in fuel remaining (fuel flow out of the tanks) or fuel consumption by the engine. Hmmm. 

 

 I (and most of us, I'll bet) would really be grateful for any physical explanations adn rationales you've turned up in your researches.

 

 Thanks!

 

 John Ackerman

 

   On Feb 7, 2007, at 11:14 AM, William Curtis wrote:

 [quote]This has come up a few time and after doing some research it turns out that the absolute *ideal* location from a true flow perspective is between the fuel servo and the distribution.  The second best location in this regard is between the mechanical fuel pump and the fuel servo.  And then the third best location from a flow perspective, is in the tunnel at the plans location.  If that was the only concern then you would go with the ideal location, however *ideal* only offers a few ml more accuracy and places the transducer in a more harsh environment.  So your accuracy may improve by .05 of a gal per hour but your transducer will be subject to earlier failure due to it being in a harsher environment.  I think the flying RV-10s have show that the tunnel location works well.William  #40237http://wcurtis.nerv10.com/  --> RV10-List message posted by: "gary" I have installed my flow-scan transducer in the tunnel like Van's said to.Now OP says it should go between the fuel servo and the spider. Anyone haveexperience with it in the tunnel? Any problems? I really don't want toreplumb it unless I need to.Gary Specketer40274 	  Quote: 	
		   	
[b]

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