REFLECTOR: Fuel Flow Sensor

Pat Shea xl340hp at yahoo.com
Fri Jul 1 13:21:41 CDT 2005


Kurt,

I'm also running the Airflow Performance boost pump
along w/ their in-line filter. I have located the
shut-off valve, filter, & pump on the engine side of
the firewall. I like your "bleed off" description of
this pump's design so as not to get it confused with
the recirculation systems which are designed to
circulate cool fuel thru much of the fuel system.
Here's a pic showing my "bleed off" return "T" just
downstream of the shutoff valve:

http://www.tvbf.org/gallery/?display=airframe_construction%2Fsump_tank%2Fretract_gear%2FDscf0055.jpg
 

Pat

--- NMFlyer1 at aol.com wrote:

> 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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