REFLECTOR: Fuel Flow Sensor

[NMFlyer1 at aol.com]

Al, and all....

I am most concerned about vapor locking as well. Perhaps I did not describe 
the fuel system well enough. 

The fuel does not flow THRU the fuel rail and back in to the system. This is 
an Airflow Performance Fuel Injection unit. The pumps are also from Airflow 
Performance and are rotary-type pumps (Not the solenoid type pumps that can heat 
the fuel all by themselves).
 I am also planning on using Avgas.

When I talked to Airflow Performance Fuel Injection, he specifically asked me 
if I had any fuel lines, pumps, etc., in the engine bay. I said NO. The only 
thing in the bay is the 6" fuel line that runs to the servo, and the injector 
lines themselves. I specifically talked to them about the return line. I 
initially had planned to return it to the sump, and asked them about the return 
flow and pressure. When they finished questioning me and determined that the 
lines were not flowing thru the engine bay, they informed me to just "T" it back 
into the pump inlet line.

I have a friend with an RV-6 that has the same pump and recirculation 
plumbing that I am working on. This is the way the people at Airflow Performance said 
to plumb it. So far, after 3 years of flying it works fine. (although their 
flowmeter is downstream of the pumps).

The pumps in my setup do have to "suck" the fuel through the flowmeter, then 
the screen filter that sits under the gear leg, then through the pumps (that 
are mounted on the bottom of the gear hoop bay, between the firewall and gear 
bulkhead). Then they push the fuel up to the top and to the engine.

The "recirculation line (probably better named a bleed off line) is compl
etely inside the gear bay area. 
The pumps, flowmeter and plumbing are even or below the top of my sump tank.  
 The filter just above that. So, everything in the system except the actual 
engine feed line is well below the "bottom of the main tanks" level.  In 
addition, I do have a screen-type racing filter in each main tank-to sump tank 
supply line. 

I appreciate the concern and information on this issue. Considering the way 
my system is plumbed, and that fuel does not recirculate through the engine 
bay, I had hoped that I  alleviated most of the areas for a vapor lock to take 
place. Of course, one can never be too safe when it comes to this issue, it 
usually shows up at the worst time. 

Keep up the good info and critiques, 

Kurt 
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