Dynon Fuel flow

Question, building an RV-8 and the dynon fuel flow sensor instructions say you need 6 inches of straight line before and after for accuracy. I have the Airflow Performance fuel injection and the only place I have that legnth is from the mechanical pump to the airflow unit below the cylinders and above the exhaust, not what I would consider ideal. How critical is this?

Fuel flow sensor location

My Flowscan sensor was originally mounted downstream from the mechanical pump, adjacent to the #4 exhaust. This bothered me as it seemed to be a fire hazard. Additionally the engine ran roughly for several minutes after a hot start. Therefore I moved the sensor to the aft baffle bulkhead inside the plenum above cylinder#3. The fuel from the fuel injection servo going to the distribution spider passes through the sensor. The sensor is wrapped in firesleeve insulation material. It was necessary to use 90 degree fitting at both the inlet and the outlet. However, I have found the accuracy to be excellent: typically .2 gallons error in a 30 gallon flight, or 0.67% error. The error is the same as it was in the original location. The post-hot start roughness still exists, but it now clears within thirty seconds. The Flowscan unit seems unaffected by the 90degree fitting.

Metered line

I ran my install with Don at AFB, the fuel line that runs from the fuel control to the purger valve then the spider runs up between the 1 and 3 cylinders. I had to get a new hose but the flow now goes from the fuel control to the flow meter which is suspended with cushion clamps on my engine mount tubes (RV-8A so there a lot of them. Then this connects to the line to the spider. Don really likes the flow meter to be in this line, not before the engine pump or fuel control but many have installed the flow meter on the firewall and other such places. This is what I did.

I passed the AW the other day and hope to fly when the weather gets better maybe next week.

This will be wrapped in fire sleeve as well.

sensor

Mine is mounted on the firewall and has a 45 degree nipple in either end. The accuracy of the flow sensor can be adjusted with a Dynon unit by changing the K factor in the setup mode. It took me about four tries to get it right, but with the 45 degree inlet/outlet nipples, I'm spot on now. My Dynon is a D180. Yours may not be adjustable. Good luck.

Skyview K factor

The K factor for the fuel flow sensor is adjustable in the Skyview.

DYNON Fuel flow answers.

Thanks for the suggetions, it was a big help.

FWIW ...

My Red Cube is located exactly where RVG8tor's (Nemo) floscan is shown in the pic. Works great and is VERY accurate. (Once I got rid of the first red cube with the leaking defective threads!) I was thankful it was in such an accessible location, given the many futile hours I spent removing and resealing inlet and outlet fittings.

Flowscan

Remember that the flowscan transducers are supposed to be mounted horizontally to have long life.The impeller in the 201 pivots on a small jewel and if not mounted horizontally can fail prematurely. marc