Hello All!
Your friendly neighborhood EI Tech support rep here!
There are really two issues in regards to EI’s specifications on flow transducer placement.
1. Accuracy of the output of the flow transducer.
2. Safety.
Issue one is pretty basic. After manufacturing flow instruments for a good number of years we have seen that flow transducers accuracy is typically better when mounted after the mechanical fuel pumps. They simply seem to prefer to have fuel pushed through them, not pulled through. The truth of it though is that many installation drawings still read as though we were still using the older Floscan 201 and 231 transducers. I have seen installs that mount the transducer between the pumps with claimed success. The Floscan units were much more sensitive in regards to mounting location, angles of fittings in and out, and attitude. Our new design will tolerate a lot more.
The other more serious issue is in regards to safety. We want to make absolutely sure that the fittings on the transducers never are subjected to conflicting vibration planes. The engine will flex in the motor mounts creating conflicting vibration planes between the engine and the airframe. This is why the “flexible line in” and “flexible line out” is called out so often. This is also why we don’t want the transducer rigid mounted, via a fitting, to a carburetor or fuel pump. A contradicting vibration plane will focus the energy directly to the fitting. It is our sincere concern that with the two conflicting vibration planes here could cause the fitting to fatigue and crack. This would be bad…and we have seen it happen….
On the bright side, we don’t care if the thing flows straight up, or if you put 90-degree fittings in and out of the transducer. Just don’t mount it upside down, flowing sharply downhill, or before the pumps.
Please let me know if you have any questions or if we may be of any assistance.
Matt Sharp