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raymondj(at)frontiernet.n
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 Posted: Sun Jul 20, 2008 11:20 am Post subject: "primer-line fuel injection" |
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Greetings Bob,
I'm very interested in any other info you have available on this system.
I have decided to put a primer in my engine even thou the carb I will be
using will have an "accelerator" pump. One of my fellow students when I was
getting my PP was able to keep his airplane in the air for approx 15 min. by
pumping the primer until the primary fuel system started working again. I'm
convinced of the value of a primer as a redundant fuel system and yours in
the only design I've seen that could be called a system to make use of it.
Raymond Julian
Kettle River, MN
"Hope for the best,
but prepare for the worst."
---
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nuckolls.bob(at)cox.net
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| Posted: Sun Jul 20, 2008 12:37 pm Post subject: "primer-line fuel injection" |
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At 02:16 PM 7/20/2008 -0500, you wrote:
| Quote: |
Greetings Bob,
I'm very interested in any other info you have available on this
system. I have decided to put a primer in my engine even thou the carb I
will be using will have an "accelerator" pump. One of my fellow students
when I was getting my PP was able to keep his airplane in the air for
approx 15 min. by pumping the primer until the primary fuel system
started working again. I'm convinced of the value of a primer as a
redundant fuel system and yours in the only design I've seen that could
be called a system to make use of it.
|
I think I published the story behind this idea but
it's been some time. It's probably worth repeating.
If you consider the "fuel injection" delivery systems
offered on GA aircraft engines for 70 years or more,
they are little more than precision orifices located outside
each intake valves and pressured up with fuel at some
value set by the mixture control.
The Beech Skipper I learned to fly in had a primer system
pressured up by the electric boost pump and controlled by
a normally closed electric valve that could be opened
by pushing in on the key while cranking the engine. Given
that Pug Piper was doing some work for Beech on the Skipper
after retiring from Piper, it would not surprise me that
this same primer system was first used on some model of
Piper.
Consider also the numbers of dark-n-stormy night stories
we've read over the decades wherein the pilot lives to tell
the tale of bringing an airplane to damage-free arrival
by stroking a primer pump after the primary fuel delivery
system fails . . . for what ever reason.
Okay, combine these three demonstrable experiments with
the notion that one can fit an engine with a 4-port
(or 6 if you have a BIG honker engine) primer system.
Assume further that you put a needle valve in an
electrically pressurized and controlled fuel source
that is adjusted for say 5 GPH of fuel flow (or whatever
suits you best). It should probably be a value in the 60%
range so that you minimize potential for damaging the
engine with a too-lean setting on one cylinder . . . but
enough power to keep you airborne. But if you get really
serious about this, you could plug your primer port fittings
and re-drill them to achieve 1/4 desired fuel flow per
port at the pressure setting of your primer pump.
Now, if you open up the primer system and pull the mixture
to idle cutoff (or the primary fuel supply is cut off
for other reasons), the throttle now becomes your mixture
control. Adjust throttle for maximum smoothness of engine
operation.
Now you have a totally redundant way to deliver much desired
fuel to a starving engine using a collection of ideas
and hardware that have been proven to perform in this task
for decades.
The sketch I showed you was for an all-electric system that
had no valves. Have a dedicated feed from left tank to primer
system. Another dedicated outlet from left tank goes to
a transfer pump that feeds the right tank. A dedicated feed
from the right tank feeds the engine. No valves, minimize
numbers of fittings. No check valves needed other than those
already built into the pumps.
One could craft a variety of fuel management systems.
I proposed one to a builder years ago that we put a low
liquid level sensor in the right tank and use it to
cross feed fuel to maintain the right tank at 1/2
full. Put low liquid level warning sensors on both
tanks when either one drops to say 1/3. When the low
fuel warning on left tank comes on, change automatic
transfer sensing on right tank from 1/2 full to
the low warning level. This will keep the right tank
at the 1/3 level until left tank is empty . . . or
one might choose to hold the left tank totally in
reserve thus keeping the standby fuel delivery system
wet at the tank end.
There are a variety of variations on this theme but
the design goal is to replace mechanical selector
valves with solid state pumps that have very few
moving parts. Further, failure of any one pump does
not put the outcome of the flight at risk because
of the dual, albeit crude second delivery system.
Bob . . .
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raymondj(at)frontiernet.n
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| Posted: Sun Jul 20, 2008 3:32 pm Post subject: "primer-line fuel injection" |
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What can I say? Thanks AGAIN for another valuable bit of education.
Raymond Julian
Kettle River, MN
"Hope for the best,
but prepare for the worst."
do not archive
---
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nuckolls.bob(at)cox.net
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| Posted: Mon Jul 21, 2008 3:51 pm Post subject: "primer-line fuel injection" |
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At 06:28 PM 7/20/2008 -0500, you wrote:
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What can I say? Thanks AGAIN for another valuable bit of education.
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I've only collected some ideas that have been laying
around on the ground for nearly 100 years and considered
how they might be combined into yet another recipe for
success.
Now, if you're considering this combination of ideas as
useful to your design goals, then YOU'RE the chef. It
will be up to you to search, select, ponder the assembly
of and ultimately test the product of your efforts. We
can help but YOU are going to be the guy who ultimately
brings the concept to fruition. If you choose to photograph
the installation . . . and share the problem solved with
making it work, then you become the expert and more
qualified than I to assist others in doing the same or
similar things.
Let us know how we may be of assitance!
Bob . . .
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A.F.Rupp(at)att.net
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| Posted: Tue Jul 22, 2008 6:39 am Post subject: "primer-line fuel injection" |
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In the Old days we used to start P&W R2800's (P-61 Martin 404)on prime and get them running before advancung mixture from idle cut off and they would run good on prime. I think if you had two point prime on a 4 or small 6 with electric boost pump it woul be sufficient.
Al Rupp
601XL - Corvair
| Quote: | At 06:28 PM 7/20/2008 -0500, you wrote:
>
>What can I say? Thanks AGAIN for another valuable bit of education.
I've only collected some ideas that have been laying
around on the ground for nearly 100 years and considered
how they might be combined into yet another recipe for
success.
|
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nuckolls.bob(at)cox.net
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| Posted: Thu Jul 24, 2008 5:58 am Post subject: "primer-line fuel injection" |
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At 02:36 PM 7/22/2008 +0000, you wrote:
| Quote: |
In the Old days we used to start P&W R2800's (P-61 Martin 404)on prime and
get them running before advancung mixture from idle cut off and they would
run good on prime. I think if you had two point prime on a 4 or small 6
with electric boost pump it woul be sufficient.
Al Rupp
601XL - Corvair
|
If one's goal was to get the engine running for
only a few seconds of fuel starved cylinders, a
few injection ports might get us by. In this
case, we're asking an engine to produce a sustained
power level sufficient to fly the airplane . . .
and it might be for an extended period of time
as well.
So I'm pretty sure one would want to install
a primer system that (as close as practical)
delivers equal quantities of fuel to each
cylinder. And unless you take the time to
accurately balance all the ports, there is
risk to one or more cylinders for the effects
of running too lean as compared to "average"
for the engine. So I think it wise to design
for, set up, and test a modest power setting
on the order of 50-60 percent.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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