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Fuel Flow Transducer Location

BSRV6

I'm New Here
I have an Rv-6 and was loking for a good places to mount my Red Cube Fuel Flow Transducer. Where are some places people have mounted them? I was thinking either the firewall or engine mount. Thanks for the help!
 
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RV-14

Here's how Van's did it on the RV-14. Click on the image to go to the source which allows you to look at it from many angles - takes a minute or two to load, so be patient.

 
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Crabed and a 0-320 lycoming.

In carbureted engines, the flow transducer should be between the mechanical pump and the carb. The exact location will be dictated by your particular setup/exhaust routing.
 
Mine is a FloScan in the cockpit, midway between fuel selector and boost pump. Yes, I know not the optimal location, but simple and easy, out of the heat of the engine compartment, and mine is always accurate to within a couple tenths of a gallon at each fill-up. Many are located in the same place without issue. A filter is reccommended upstream of it, however, as it has a small orifice.

Chris
 
vapor lock?

For those with their fuel flow transducer upstream of the fuel pump, are you not concerned about vapor lock?
 
There are literally 1000's of locations and opinions of where to mount the flow transducers. Typically for carbed engines, between the mechanical pump and the carb is the most optimum location. Injected engines, between the servo and the flow divider. Our opinion is based on data from AirFlow Performance. Don and I have talked about these locations and our theories for them. Don has the flow bench data from his testing.

Firewall locations, although they work for some builders, is not the optimum location.

Tom
 
Others have mounted one in each wing root, and have flow for each tank independently. With the right fuel gauge, your fuel level measured by the flow out of each tank can be more accurate than either floats or capacitive senders.
 
For those with their fuel flow transducer upstream of the fuel pump, are you not concerned about vapor lock?

No - it is under pressure there. It is under suction before the mechanical pump.

Edit - Oops, dyslexic I suppose, upstream (ahead in the flow path) from the mechanical pump will degrade the temperature tolerance and/or vapor pressure tolerance of the fuel system. Mine is between the mechanical pump and the injected fuel distributor. Sorry Michael, thanks for the save.
 
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EI's installation manual for the FP-5 meter clearly specifies to install the Red Cube between the engine driven pump and carburetor. I am having mine mounted on the firewall, but piped between the engine driven pump and carburetor...per EI's drawing.

My anecdotal understanding is that the suction flow and discharge flow vs time characteristics for the engine driven pump may not be identical. There may be some built-in volumetric capacitance inside the pump. But I have not seen this characteristic documented anywhere. I will just stick with EI's installation specs.
 
No - it is under pressure there. It is under suction before the mechanical pump.

For the sake of clarity, "upstream" is by most definitions "before" the mechanical pump.

Anything before the mechanical pump is "upstream" and therefore on the suction side. Given the recent threads by DanH and others looking at the incredibly small internal passages of these devices, any suction side mounting should be considered a really bad idea.

Yes, there are thousands flying with them on the suction side - that does not change the fact that its a bad idea. After all, there are still people in this day and age that take up smoking cigarettes too. Just because people do something does not make it smart.
 
For the sake of clarity, "upstream" is by most definitions "before" the mechanical pump.

Anything before the mechanical pump is "upstream" and therefore on the suction side. Given the recent threads by DanH and others looking at the incredibly small internal passages of these devices, any suction side mounting should be considered a really bad idea.

Yes, there are thousands flying with them on the suction side - that does not change the fact that its a bad idea. After all, there are still people in this day and age that take up smoking cigarettes too. Just because people do something does not make it smart.

While I agree the flow sensor is best located between the throttle body and the spider, I offer that this is not a ?do or die? issue.

As there are many RV-10s flying with the flow sensor in the tunnel per the Van?s plans (mine included) we have data available on flow accuracy in this location. For my plane, the fuel total has always been within 0.2 gallons on fill up.

My first plane had it just before the spider and it worked fine. Still deciding where to put it on the new RV-8 project. As I know accuracy is good in various locations, I?m now biasing the decision more toward best place for heat, vobration and mechanical aspects of the mount.

Carl
 
Accuracy is not the issue. The consideration that makes a suction side installation undesirable is the incredible restriction that it creates. We go to great lengths (or should) to minimize suction side restriction by minimizing the use of 90 degree fittings, buy high flow filters, reduce the length of tube, etc... To then throw this device with a pinhole through the middle of it right in the whole mess defeats all of that prior design elegance.

The harder the fuel pump has to draw on this restriction, the lower the system pressure is. The lower the pressure is, the easier that vaporization occurs. Throw some warm temps and/or a low vapor pressure fuel and suddenly you have idle problems and/or vapor lock.

As many will attest it does work, but sometimes it does not.
 
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ultrasonic fuel flow sensors

We just need to knock one digit off the price of these ultrasonic fuel flow sensors and then it won't matter much where we put them. I'm sure they'd be even happier inside the cockpit.

http://www.reventec.com/product-category/flow-sensors/

Flowsonic-Elite-Ultrasonic-Fuel-Flow-Sensor-300x300.jpg
 
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