Fuel Filters, Wing Tanks

[djmc4344]

I'm right in the middle of changing out all my fuel lines, getting rid of the orginal factory stuff. Is it over kill or a good idea to have fuel filters from the wing tanks to just before the header tank and one filter just before the carb inlet. Opinions and thoughts on this appreciated.

Thanks

[Av8r3400]

My opinion and its only one man's opinion:

I do not like the idea of a filter between the wing and header tanks. The only flow there is via gravity. A small amount of water contamination could block the flow through these filters. Personally, I only like a filter where a pump provides positive flow through it.

[Dave S]

Hi Dan,

I unequivocally second Larry's comments. There should be no filters, for that matter - no partial restrictions of any kind, in the line between the main tanks and the header tank.

I had to experiment with this to settle the issue for myself. During my fuel system testing BEFORE first flight I experimented with a filter on each side. I found that all you had to do to get the fuel flow to stop is get a slug of air into one of the filters - the combination of fuel wetted filter and air sealed against the rather small amount of head pressure (remember the header tank vents back to the right wing tank balancing off most of the potential head pressure). This caused the flow to stop - it could be restarted only by significantly pressurizing the wing tank to overcome the cavitated wet filter. THE FILTERS WERE REMOVED FROM BETWEEN THE HEADER TANK AND WING TANKS before the first flight and the whole assembly replaced with a single one piece hose on each side.

You might think I am overstating the situation a bit - if you saw it happen in front of your face - I don't think you would consider deviating from the design specification.

That's just my opinion - based on experimentation with the setup.

Sincerely,

Dave S
KF7 Trigear

[Dorsal]

I support the last two posts, keep in mind that the tanks only balance with the differential pressure between them, that may only be a few inches of head for significant asymmetric draw. It does not take much (as pointed out above) to cause this to occur.

[Mnflyer]

Count me in with the 3 previous posters I agree 100% no filters on the tank lines.

[djmc4344]

Thanks for the advice guys, I think I'll go with one good filter.


I currently have a clear filter on each down line and one just before the carb. I have been experiencing unequal flow especially from the left tank it seems to draw down much faster than the right take. I think it may have something to do with filters I'm using.

I'm changing the tank hose to header to 3/8 I.D, I have 5/16 aluminum tube to the firewall. Then I will install either 5/16 or 1/4 I.D line from the firewall to the carb. The carb inlet is 1/4" I think.

[DesertFox4]

Sorry guys, my model 4's been operating just fine for 750 hours with filters and valves in the fuel lines between wing tanks and header tank. My previous model 3 , same thing for 1400 plus hours. Several Kitfox in "the Valley" are set up the same way with thousands of trouble free hours.
I do use blue Tygon type fuel lines so I can always see my fuel flow on both tanks and see-through filters. So far so no feeding issues in any attitude possible including limited aerobatics.

[5770phil]

Hi, my name is Phil and I have a Kitfox 3 and installing a 2180 VW. Can you tell how you vented your header tank and to where as I am not sure as I have had a number of people with different ideas. Thanks.

[cap01]

phil , not sure how the III are arranged with the gas tanks but the model IV vents the header tank to the inbd side of the right wing tank .

[5770phil]

Thanks Chuck, how is it plumbed to to right wing tank