Today's Message Index:
----------------------
1. 08:54 AM - 914 fuel restrictor info (Ronald J. Parigoris)
2. 01:30 PM - Re: 914 fuel restrictor info (Fred Fillinger)
3. 02:14 PM - Re: 914 fuel restrictor info (Michael Parkin)
4. 09:57 PM - Re: 914 fuel restrictor info (Fred Fillinger)
Message 1
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| Subject: | 914 fuel restrictor info |
--> Europa-List message posted by: "Ronald J. Parigoris" <rparigor@suffolk.lib.ny.us>
Hey Guys
OK kinda sortta have a better handle on 914 carburation. First off a turbo motor
will run with very little fuel pressure, like gravity feed. It will only run
however at ambient pressure or less. If you boost the motor will quit. The reason
is if you boost the pressure in the venturi, it will blow through main and needle
jets! You need to keep the pressure in the float bowl above that of the boost to
allow Berneulli to suck.
They have a fuel pressure regulator to handle this task. If it fails and fuel
pressure drops, you may be able to continue to make noise if you throttle back
to
ambient pressure or less.
The restrictor provides backpressure and return flow to fueltank. If restrictor
clogs, fuel pressure regulator would still operate, but you may cause cavitation
in the fuel pump/s. Even though the regulator is only allowing the correct
pressure to get to the float bowl, if you had a fuel pressure guage at the pump,
you would see a rise in fuel pressure. Vapor lock could occur with no excess
flow. He said you should have a fuel pressure guage on all 914 installiations.
Phil Lockwood said he dosen't think he has seen a full blockage. Partial usual
makes motor run terrable. He said blockage is rare. On inital assembly not a bad
idea at all to blow out fuel lines, and prior to install of restrictor, to let
fuel pumps run and let a gallon or so of fuel to run through system.
There ya have it. A 914 is not fuel injected, you just need to turbocharge the
float bowl a bit over full boost pressure so the venturi works.
Ron Parigoris
Message 2
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| Subject: | Re: 914 fuel restrictor info |
--> Europa-List message posted by: Fred Fillinger <fillinger@ameritech.net>
> Hey Guys
>
> OK kinda sortta have a better handle on 914 carburation. First off a turbo motor
> will run with very little fuel pressure, like gravity feed. It will only run
> however at ambient pressure or less. If you boost the motor will quit. The reason
> is if you boost the pressure in the venturi, it will blow through main and needle
> jets! You need to keep the pressure in the float bowl above that of the boost
to
> allow Berneulli to suck.
>
> They have a fuel pressure regulator to handle this task. If it fails and fuel
> pressure drops, you may be able to continue to make noise if you throttle back
to
> ambient pressure or less.
>
> The restrictor provides backpressure and return flow to fueltank. If restrictor
> clogs, fuel pressure regulator would still operate, but you may cause cavitation
> in the fuel pump/s. Even though the regulator is only allowing the correct
> pressure to get to the float bowl, if you had a fuel pressure guage at the pump,
> you would see a rise in fuel pressure. Vapor lock could occur with no excess
> flow. He said you should have a fuel pressure guage on all 914 installiations.
>
> Phil Lockwood said he dosen't think he has seen a full blockage. Partial usual
> makes motor run terrable. He said blockage is rare. On inital assembly not a
bad
> idea at all to blow out fuel lines, and prior to install of restrictor, to let
> fuel pumps run and let a gallon or so of fuel to run through system.
>
> There ya have it. A 914 is not fuel injected, you just need to turbocharge the
> float bowl a bit over full boost pressure so the venturi works.
>
> Ron Parigoris
If I understand the poorly translated Deutsch: The 914's carbs have
garden-variety float bowls, whose airspace is vented to the airbox. The
airbox will see as high as 38.4" MP, down to something less than
ambient. The regulator maintains fuel pressure relative to airbox
pressure, at 2.2-5.1 psi, 3.6 nominal, above airbox.
There must be no restrictor in the return line, and back pressure in the
return plumbing (which will include tank pressure head and fuel vent
pressure in flight) cannot exceed 1.5 psi to prevent overriding the
float valves and flooding. If the return line is blocked, regulation
totally ceases and the carbs will more assuredly flood -- around 20 psi
or so.
Regards,
Fred F.
Message 3
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| Subject: | Re: 914 fuel restrictor info |
--> Europa-List message posted by: "Michael Parkin" <Mikenjulie.Parkin@btopenworld.com>
Hi Guys,
As they say 'Allo Allo'. "Please listen I shall say this only once - there
is NO restrictor in the return fuel line on a Europa/Rotax 914 installation"
regards,
Mike
----- Original Message -----
From: "Ronald J. Parigoris" <rparigor@suffolk.lib.ny.us>
Subject: Europa-List: 914 fuel restrictor info
> --> Europa-List message posted by: "Ronald J. Parigoris"
<rparigor@suffolk.lib.ny.us>
>
> Hey Guys
>
> OK kinda sortta have a better handle on 914 carburation. First off a turbo
motor
> will run with very little fuel pressure, like gravity feed. It will only
run
> however at ambient pressure or less. If you boost the motor will quit. The
reason
> is if you boost the pressure in the venturi, it will blow through main and
needle
> jets! You need to keep the pressure in the float bowl above that of the
boost to
> allow Berneulli to suck.
>
> They have a fuel pressure regulator to handle this task. If it fails and
fuel
> pressure drops, you may be able to continue to make noise if you throttle
back to
> ambient pressure or less.
>
> The restrictor provides backpressure and return flow to fueltank. If
restrictor
> clogs, fuel pressure regulator would still operate, but you may cause
cavitation
> in the fuel pump/s. Even though the regulator is only allowing the correct
> pressure to get to the float bowl, if you had a fuel pressure guage at the
pump,
> you would see a rise in fuel pressure. Vapor lock could occur with no
excess
> flow. He said you should have a fuel pressure guage on all 914
installiations.
>
> Phil Lockwood said he dosen't think he has seen a full blockage. Partial
usual
> makes motor run terrable. He said blockage is rare. On inital assembly not
a bad
> idea at all to blow out fuel lines, and prior to install of restrictor, to
let
> fuel pumps run and let a gallon or so of fuel to run through system.
>
> There ya have it. A 914 is not fuel injected, you just need to turbocharge
the
> float bowl a bit over full boost pressure so the venturi works.
>
> Ron Parigoris
>
>
Message 4
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| Subject: | Re: 914 fuel restrictor info |
--> Europa-List message posted by: Fred Fillinger <fillinger@ameritech.net>
Michael Parkin wrote:
>
> Hi Guys,
>
> As they say 'Allo Allo'. "Please listen I shall say this only once - there
> is NO restrictor in the return fuel line on a Europa/Rotax 914 installation"
We get that on cable in this small part of the States! The show's a
riot, say-only-once Michelle is cool, and interestingly self-bashes
Brits more than the French. Like "South Park" here with British reserve.
Anyway, due to variability of absolute fuel pressure, I did a circuit on
"breadboard" that differentially measures fuel pressure (rheostat type
sender) verses airbox pressure (electronic sensor, automotive part for
turbo cars). It lights one of a strip of green, yellow, and red LEDs,
with flashing reds and aural alarm. It works great, but most breadboard
kludge ideas do initially. :-)
Before I commit to printed circuit board and deal with temp
stabilization issues in final components, how does a simple fuel
pressure gauge behave on the the 914? From the data in Rotax docs, for
most ranges of operation, the reading should be usable. In full boost,
does the needle go a little wild? What happens at high altitudes?
Best,
Fred F.
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