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R912UL Initial Engine Test Run

 
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pwmac(at)sisna.com
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PostPosted: Tue Sep 05, 2006 6:27 am    Post subject: R912UL Initial Engine Test Run Reply with quote

True, the engine theoretically should run a hotter due to properties
that conduct heat less the water or 50/50 EG.
Insulating the fuel lines will capture the heat and make vapor lock
worse. All insulation does is slow the heat transfer process - wont
make the lines cooler. Better to figure out how to get some cool air
to them or re route them to a cooler place. A pretty easy thing to
solve, but for a static test there is more heat due to the plane not flying.
Rotax has specifically specified a formulation for the Evans that is
compatible with their coolant flow and pump, so the engine should be
OK. Did you see a 30 deg F rise in oil temp? IMO, A pretty big increase.
Paul
=================

At 10:32 PM 9/4/2006, you wrote:
[quote]

Beware of using the evans coolant in a system (aircraft) not specifically
designed for it. I ended up in a baaaad situation with vapor lock (with
100LL!!! And insulated fuel lines) after switching to evans. Evans, while
not boiling until well over 300F, also does not cool as well. You WILL see
at least 30F increase in normal operating temps with the evans coolant.

-Bruce

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bjohnson(at)satx.rr.com
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PostPosted: Tue Sep 05, 2006 7:12 am    Post subject: R912UL Initial Engine Test Run Reply with quote

[quote] --

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Thom Riddle



Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

PostPosted: Wed Sep 06, 2006 3:14 am    Post subject: R912UL Initial Engine Test Run Reply with quote

Back in the dark ages when I was a drag racer in the very hot summer
days in the south, my cars would sometimes get vapor lock. The solution
for us was to install an electric fuel pump at the tank to make sure
the whole fuel system was pressurized to something above ambient
pressure from the tank to the carburetor instead of below ambient
pressure due to the suction action from the engine mounted mechanical
fuel pump. Rotax has the engine mounted fuel pump which draws by
suction from the tank which is frequently mounted lower than the
engine. Many aircraft have electric fuel pumps as either back-ups or
required due to location of the fuel tanks. If your airplane has an
electric fuel pump located such that it pressurizes virtually the whole
fuel system (except the tank), try turning on this boost pump to
eliminate the vapor lock. The increase in pressure was always enough to
solve the vapor lock problem on our old dragsters and may work for your
airplane.

Thom in Buffalo


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pwmac(at)sisna.com
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PostPosted: Wed Sep 06, 2006 5:43 am    Post subject: R912UL Initial Engine Test Run Reply with quote

Thom,
Good point. Hard to believe there are planes in use that do not have
a backup electric fuel pump mounted low in the system. I am a Kitfox
guy and many of these planes have the electric backup as well as a
fuel return. The standard deal is to operate the electric pump for
prestart, takeoff, & landings. The prestart e-fuel pump operation
allows the fuel bowls to both fill and aids in a less rough start.
The reduction in engine roughness is because the electric pump allows
both carb bowls to fill and thus all 4 cylinders fire at start
instead of one bank lagging due to slower filling of the carb bowls.
The return provision is built into the Kitfox design because they
wanted to provide for fuel injected engines (IO240) which all require
a fuel return. If your plane does not have the extra fitting in the
tank then a mod will to the tank would be required for the return.
Vapor lock on this design have not had any reported vapor lock.
IMO, the return fuel line is overkill for a carb engine. Good design
practice would always indicate for a backup fuel pump.
Regards, Paul
PS, One has to choose the electric pump that meets the Rotax spec for
pressure so as to avoid overpowering the carbs. Most people use a
Facet and it installs in series with the mechanical Rotax pump. It
does not need a bypass for the engine to operate with the electric
pump off. Paul
======================

At 05:14 AM 9/6/2006, you wrote:
Quote:


Back in the dark ages when I was a drag racer in the very hot summer
days in the south, my cars would sometimes get vapor lock. The
solution for us was to install an electric fuel pump at the tank to
make sure the whole fuel system was pressurized to something above
ambient pressure from the tank to the carburetor instead of below
ambient pressure due to the suction action from the engine mounted
mechanical fuel pump. Rotax has the engine mounted fuel pump which
draws by suction from the tank which is frequently mounted lower
than the engine. Many aircraft have electric fuel pumps as either
back-ups or required due to location of the fuel tanks. If your
airplane has an electric fuel pump located such that it pressurizes
virtually the whole fuel system (except the tank), try turning on
this boost pump to eliminate the vapor lock. The increase in
pressure was always enough to solve the vapor lock problem on our
old dragsters and may work for your airplane.

Thom in Buffalo


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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:

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