Fuel line to and from fuel flow transducer

ArVeeNiner · #1 11-05-2009, 11:24 PM

I have put my fuel flow transducer in line between the mechanical fuel pump and the carb as per page 10 of this document: http://www.jpinstruments.com/700-800_FF_install.PDF

The Dynon instructions state that you need to have 6" of straight line before and after the transducer. In trying to meet this requirement, my distance between the fuel line and the exhaust was unacceptably small. I have been able to move the line to a minimum of 1 1/8" from the exhaust which is still a bit close for comfort. It I totally ignore the 6" of straight hose before and after the transducer and cut my fuel line much shorter than it is, I can increase my distance to over 2" from the heat source.

My question is, just how important is this 6" of straight line requirement to the accuracy of the fuel flow transducer?

Mathew Sharp · #2 11-06-2009, 10:17 AM

As far as I know Dynon distributes both the FloScan 201B as well as EI's FT-60.

The FloScan unit is much more sensitive to the angles/fittings entering and exiting the unit. EI's unit does not care. You can run 90 degree fittings in and out of ours without problems.

JPI does not sell EI's FT-60

Maybe you can get Dynon to trade you for a FT-60?

Good luck!

Matt

Kevin Horton · #3 11-06-2009, 11:03 AM

Is the EI FT-60 compatible with the Grand Rapids EIS-4000?

Mathew Sharp · #4 11-06-2009, 11:12 AM

Sure is!

a FT-60 can be used anywhere that a FloScan 201B is also recommended.

Thanks for the interest!

Matt

Mel · #5 11-06-2009, 01:20 PM

Quote:

Originally Posted by Mathew Sharp

The FloScan unit is much more sensitive to the angles/fittings entering and exiting the unit. EI's unit does not care. You can run 90 degree fittings in and out of ours without problems.

Matt,
I'm about to replace my FloScan with the EI "red cube".
I have heard that your transducer prefers to have fuel "pushed" through rather than "pulled" through. My FloScan have been working great between the selector valve and the boost pump for over 16 years. Can I put the EI unit in the same place?

Brantel · #6 11-06-2009, 01:22 PM

Matt,

Thanks for being on the ball!

Bubblehead · #7 11-06-2009, 04:18 PM

I use a FloScan unit with about 2" straight run in and out and is accurate to better than 1% (.1 gallons off in 10 gallons of flow). That's measured performance after about 80 hours of flying with it. Maybe others have had problems with it but I think some of it is old wives tales.

The unit is mounted directly to a bulkhead fitting so whatever turbulence it gets from that does not effect it.

ArVeeNiner · #8 11-08-2009, 11:30 PM

Well, despite spending a very exciting weekend at my 8 year old daughter's soccer jamboree, I was able to rework my fuel line and now I have a much bigger space between the exhaust and the fuel line. I cut about 4" from the fuel line and rerouted things. The fuel flow transducer is slightly off of horizontal and I only have about 4" of straight line coming out of it and less than that going into it. I think fire safety (or vapor lock avoidance) is more important than dead nuts accuracy of the fuel flow. From what I've read, it seems that I most likely won't lose much in the way of accuracy anyway. Besides, I also have what are advertised as very accurate capacitance fuel senders and of course there is the time tested digital timer for estimating fuel consumption. Here is how it looks now:

From the bare exhaust pipe (no shield) to the bare fuel line (no fire sleeve) the closest I get now is about 1 5/8" and this is to the tailpipe. I reasoned that it's best to maximize the distance from the portion of the pipe at the cylinder. My line is over two inches away from this area.

I bought the $11 heat sheild from Van's. You can see it on the left but now that I've rerouted everything, it doesn't do a heck of a lot. Then, using Van's design as a guide, I made my own out of a piece of galvanized sheet but I made it much longer. I put it at the closest point and you can see it at the lower center of the picture.

Any opinions or suggestions?

By the way, my daughter's team, the Thundercats, came in second to the dreaded Soccer Divas. It was a fun weekend!

ronschreck · #9 11-09-2009, 04:23 AM

Quote:

Originally Posted by ArVeeNiner

I bought the $11 heat sheild from Van's. You can see it on the left but now that I've rerouted everything, it doesn't do a heck of a lot. Then, using Van's design as a guide, I made my own out of a piece of galvanized sheet but I made it much longer. I put it at the closest point and you can see it at the lower center of the picture.

Happy to see others making their own heat shields. You can duplicate the $11 Van's shields for about 50 cents and 10 minutes of labor. Plus you can make them any size to fit your particular application.

Mathew Sharp · #10 11-09-2009, 12:28 PM

Quote:

Originally Posted by Mel

Matt,
I'm about to replace my FloScan with the EI "red cube".
I have heard that your transducer prefers to have fuel "pushed" through rather than "pulled" through. My FloScan have been working great between the selector valve and the boost pump for over 16 years. Can I put the EI unit in the same place?

For the most part "pushed" through rather than "pulled" through is a conventional wisdom thing that may be beyond me in terms of the physics and fluid dynamics.

What I would tell you is that if your FloScan has been working fine in that location there is no reason to think that the EI unit would not work as well.

The simple fact is that for the STC'd installs they require that either unit be after the pumps period.

But on the experimental side I have had many customers report success in the location you describe.

I might try it before I ever recommended moving it.

Good luck!

Matt