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R912UL Initial Engine Test Run

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pwmac(at)sisna.com
Guest

Posted: Tue Sep 05, 2006 6:27 am Post subject: R912UL Initial Engine Test Run

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
Guest

Posted: Tue Sep 05, 2006 7:12 am Post subject: R912UL Initial Engine Test Run

[quote] --

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Thom Riddle

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

Posted: Wed Sep 06, 2006 3:14 am Post subject: R912UL Initial Engine Test Run

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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_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

pwmac(at)sisna.com
Guest

Posted: Wed Sep 06, 2006 5:43 am Post subject: R912UL Initial Engine Test Run

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

- The Matronics RotaxEngines-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:

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