Fuel Flow fluctuations

[alcladrv]

I have my Floscan fuel flow transducer mounted just like the picture above. Overall, it seems to be reasonably accurate (within 5% or less).

My beef with the installation is that the fuel flow indication will fluctuate over a 2 to 3 gph range, e.g. 7 to 10 gph after I've leaned it to about 8 to 8.5 gph depending on rpm and altitude. Would a different location give a steadier indication? Anyone with operational experience care to share?

I've got about 230 hrs. on my ECI O-360 carb engine installation with a Sensenich fixed pitch prop on my -7A.

Mike

[Jim Ellis]

Hi Mike,

I have the same engine/prop setup and had the same problem with fluctuating fuel flow readings you describe. My Floscan sensor is mounted like yours in the photo.

After some online research I found info that suggested that the readings could be affected by back pulses from the mechanical fuel pump that caused the rotor in the fuel sensor to stop or even back up causing the sensor to "miss-count".

I first installed a Matronics Pulse Dampener after the sensor but I saw no improvement. I removed the Pulse Dampener and installed an in-line fuel filter after the sensor. That seemed to solve the problem..readings at all fuel flows are now steady. I think just about any large filter would work, but here's one I found that's not too expensive and the ends can be drilled and safety wired if you wish.

I won't promise that it will work or even that the cause of the problem is as I described...but it worked in my case.

[Captain Avgas]

Originally Posted by alcladrv

I have my Floscan fuel flow transducer mounted just like the picture above. Overall, it seems to be reasonably accurate (within 5% or less).

My beef with the installation is that the fuel flow indication will fluctuate over a 2 to 3 gph range, e.g. 7 to 10 gph after I've leaned it to about 8 to 8.5 gph depending on rpm and altitude. Would a different location give a steadier indication? Anyone with operational experience care to share?

I've got about 230 hrs. on my ECI O-360 carb engine installation with a Sensenich fixed pitch prop on my -7A.

Mike

Try reading this thread.
http://www.vansairforce.com/communit...ad.php?t=11698
Incidentally both JPI and Electronics International state that in order to minimise fluctuations and errors the transducer should be located AFTER the mechanical fuel pump..... less chance of vapour lock as well.

Incidentally, is that an aluminium tube fuel line I see....with aluminium fittings...and no fire sleeve. If so, I'd be MUCH more worried about that than I would about fluctuation in transducer read-outs.

[alcladrv]

Thanks for your input, Bob. I'd read the thread you pointed out before I made my post. From the different posts, it seems there really wasn't a consensus on where to install the transducer to get the best performance. That's why I asked for input from those with operational experience.

By the way, thanks for your input, Jim.

This is my first plane, so I'm looking for ways to improve its safety and performance. So far, it's performed well and more than met my needs. Any other operationally-based opinions?

Thanks,

Mike