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chaztuna(at)adelphia.net
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 Posted: Wed Apr 19, 2006 5:20 pm Post subject: Fuel Flow Transducer-Injected |
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Paul
This has been discussed on the Yahoo RV8 List several times before.
JPI has an Acrobat file installation manual. In it, they recommend
installing the transducer between the servo and the fuel distributor.
It gets installed in the middle of a flex hose, so it isn't subjected
to all the vibration of the engine. Check out the document on the web
link below. Look at page 8
http://www.jpinstruments.com/700-800_FF_install.PDF
Charlie Kuss
| Quote: |
First question, where's a good place to put this in
the stream of fuel? I'm not too savvy on injected
engines.
While talking with Electronics International today, I
was told that since there is a return of unused fuel,
I'll need TWO transducers and a little box that
computes the unused fuel. This adds about $300 to the
price of my fuel flow, and am wondering if it's worth
it now. Thoughts?
Paul Besing
RV-4
N73DD
Arizona (For Now)
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Bob Barrow
Joined: 11 Jan 2006
Posts: 29
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| Posted: Wed Apr 19, 2006 6:06 pm Post subject: Fuel Flow Transducer-Injected |
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I can understand that any restriction upstream of the engine fuel pump might
tend to increase the possibility of vapour lock. However you would think
that the AFP electric fuel boost pump itself would cause some sort of
restriction....surely the filter would. And then there's the people who also
use gascolators...or additional filters in the wing roots etc. Wouldn't all
of these things create some degree of resistance to flow. Why is the fuel
flow transducer being singled out...does it present an exceptional
resistance to flow. Have there been any reported cases of vapour lock
associated with locating the transducer upstream of the engine fuel
pump....or is this just more "worry bucket" stuff.
Does anybody have any pix of their fuel transducer mounted between the servo
and the divider (and off the engine as has been recommended). Have the
people who have done this had universally good metering results...despite
the fact that they "may" not have the prerequisite 5" of straight line
before and after the transducer and may not have it mounted vertically as
recommended by the manufacturer.
Decisions, decisions...phew.
New year, new job there's more than 100,00 jobs at SEEK
http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Eseek%2Ecom%2Eau&_t=752315885&_r=Jan05_tagline&_m=EXT
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Bob Collins
Joined: 11 Mar 2006
Posts: 470
Location: St. Paul, Minnesota
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| Posted: Thu Apr 20, 2006 4:23 am Post subject: Fuel Flow Transducer-Injected |
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| Quote: |
I can understand that any restriction upstream of the engine
fuel pump might
tend to increase the possibility of vapour lock. However you
would think
that the AFP electric fuel boost pump itself would cause some sort of
restriction....surely the filter would.
|
I believe there's an automatic bypass on the AFP in the event of a blockage
in the filter.
On question though, the terms people are using here remind me of when I'm in
a pattern and somebody says "NXXXX, on the GPS approach to Runway XYZ. Of
course, that does absolutely no good to anybody who doesn't know the GPS
approach." So when you give these places of where the thing should e
installed, for those of us who haven't yet really tackled this task, could
you provide a little more information regarding its exactly location in
relation to the fuselage and firewall? It'd be a big help.
Thanks
Bob Collins
RV Builder's Hotline
http://home.comcast.net/~rvnewsletter/
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_________________
Bob Collins
St. Paul, Minn.
Letters from Flyover Country
http://rvnewsletter.blogspot.com/ |
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dwight(at)openweave.org
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| Posted: Thu Apr 20, 2006 6:44 am Post subject: Fuel Flow Transducer-Injected |
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Again ... I'm just passing on information I learned from others, and have
not performed this installation myself. But this is how I intend to do it.
The place that I have been instructed to install my flowscan is between the
throttlebody and the flow divider. In fact, the suggestion is to install it
very near the flow divider on the line that runs between the cylinders. There
will be a straight run out from the throttle body up to the Flowscan, then
out of the Flowscan will be a short straight run and then from the transducer
a line runs to the purge valve, and with the purge valve plumbed into the
flow divider inlet. The whole transducer assembly should be wrapped in
firesleeve to protect it from heat.
The impression I have been left with is that this makes for a simple install
with good results. It measures only that fuel that metered out of the servo,
is not affected (therefore) by pressure changes from turning on/off the boost
pump, and does not create a restriction on the suction side of the engine
driven pump. It -does- mean that when you purge the line at start up and shut
down a small amount of fuel will be counted as "consumed" even though it is
returned to the supply lines .. but that is going to be only a small amount
of fuel compared to the total consumed during a flight, and thus results in
only a small percentage error. And .. most importantly .. that error will be
on the conservative side meaning you will have -slightly- more fuel than your
equipment thinks it has rather than less. That is the "right kind" of error
to have, if you are going to have any error. 
If someone has better information ... please feel free to correct any mistakes
I might have made. But this is my memory of what was shared at the Airflow
class.
-- Dwight
On Thu Apr 20 08:19:55 2006, Bob Collins wrote :
| Quote: | I believe there's an automatic bypass on the AFP in the event of a blockage
in the filter.
On question though, the terms people are using here remind me of when I'm in
a pattern and somebody says "NXXXX, on the GPS approach to Runway XYZ. Of
course, that does absolutely no good to anybody who doesn't know the GPS
approach." So when you give these places of where the thing should e
installed, for those of us who haven't yet really tackled this task, could
you provide a little more information regarding its exactly location in
relation to the fuselage and firewall? It'd be a big help.
Thanks
|
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chaztuna(at)adelphia.net
Guest
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| Posted: Thu Apr 20, 2006 9:40 am Post subject: Fuel Flow Transducer-Injected |
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Bob,
Check out JPI's installation instructions. They use the same
FlowScan transducer. Check out pages 8-10 on the web document below
http://www.jpinstruments.com/700-800_FF_install.PDF
FYI, folks use gascolators on carbureted engines. They are a
relatively low pressure system (5 psi) versus 25 psi for the Bendix
and AFP fuel injection systems. That's an apples to oranges
comparison. Yes, installing the fuel filter before the aux fuel pump
will create a slight restriction. However, these filters use a SS
mesh screen, not a paper element like cars do, so the restriction is
slight. The transducer is small and contains a close tolerance
trubine. There is a greater possibility of cavitation (air bubbles)
if this is installed before either of the pumps.
I spoke to an engineer at FlowScan, he said that the 5" rule is not
critical, so long as you aren't installing a 90 degree fitting at
either end of the transducer. As you have noted, others have
installed the transducer behind the firewall with success. If it's
installed behind the firewall but after the electric aux pump, any
cavitation issues can be resolved by engaging the electric pump. The
transducer then goes from being on the suction side of the system, to
the pressure side.
The engineer I spoke with stated that the orientation issue is to
prevent debris from jamming the transducer.
Charlie Kuss
| Quote: |
I can understand that any restriction upstream of the engine fuel pump might
tend to increase the possibility of vapour lock. However you would think
that the AFP electric fuel boost pump itself would cause some sort of
restriction....surely the filter would. And then there's the people who also
use gascolators...or additional filters in the wing roots etc. Wouldn't all
of these things create some degree of resistance to flow. Why is the fuel
flow transducer being singled out...does it present an exceptional
resistance to flow. Have there been any reported cases of vapour lock
associated with locating the transducer upstream of the engine fuel
pump....or is this just more "worry bucket" stuff.
Does anybody have any pix of their fuel transducer mounted between the servo
and the divider (and off the engine as has been recommended). Have the
people who have done this had universally good metering results...despite
the fact that they "may" not have the prerequisite 5" of straight line
before and after the transducer and may not have it mounted vertically as
recommended by the manufacturer.
Decisions, decisions...phew.
New year, new job there's more than 100,00 jobs at SEEK
http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Eseek%2Ecom%2Eau&_t=752315885&_r=Jan05_tagline&_m=EXT
|
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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