Wendell , I really don't know how much heat the fuel picks up.  Depends on a number of factors. 

 However, a low pressure (4-6 psi) boost pump, increases the pressure in the header tank and suppresses (in my case) any tendency of the fuel to percolate.  I used the one Van recommends for the RV series - a facet fuel pump with 37 deg fitting (vice the 45 for auto installations).   They are used on a number of different aircraft.  Here is some more information about the pump, I would recommend the model   40106 which has up to 6 psi output.

 

http://www.aircraftspruce.com/catalog/eppages/facetpumps.php

 

Before going further, I think its safe to say, that having a system that has the high  pressure EFI pump in the fuel tank and  that returns the heated fuel back to a  main tank which acts as a heat sink is probably the safest approach from a heated fuel stand point.  I personally did not want to run more fuel lines (particularly high pressure ones) through the cockpit area.  If you switch tanks then that would necessitate switching both main line and return line to get the fuel back to the correct tank.  Also the ideal of a replacing a pump inside the tank (if needed) did not appeal. 

 

Tracy Crook uses a system whereby he feeds the engine from one wing tank only and simply transfers fuel from the second wing tank into the feed tank (one big header tank {:>)).  Works fine as attested to by his 17 years of rotary flying.

 

There are other good, reliable and safe approaches, just need to think them all through regarding fuel flow, leaks, vapor lock, etc.

 

 

 Having said that, here is my system:

 

I have two high pressure fuel pumps each with its own feed from the bottom of my tiny header tank (important that the header tank be air tight and as low in the system as you can get it and feed to pumps be as short as possible), each pump has its own high pressure (Stock GM EFI filter with saganaw fittings and O ring) after the filters the line from each is "Y" into a single line to feed first the primary injector and then the secondary before returning to a pressure regulator the output of which dumped back into the header tank.  Each pump has its own power feed and switch.

I use An-6 stainless steel braided lines for all fuel lines and the 4 injectors feed in series off of it - no problems with adequate fuel flow (at least up to 200HP).

 

 

The boost pump is hooked into the line between the wing tank feed and the header tank.  I take off and land with both EFI pumps and the boost pump on.  My standard practice.

 

That's about it.  Yes, copying a successful system is a proven way - but, as I tell folks, unless you have an exact duplicate in all details - you have a different system and it may respond differently than the one you copied. 

 

Ed

 

 

----- Original Message -----

From: Wendell Voto

To: Rotary motors in aircraft

Sent: Monday, August 27, 2007 12:46 AM

Subject: [FlyRotary] Re: need help

 

 

Ed,

Thanks for the reply, now I believe I'll go with a smaller header tank and make it aluminum or maybe go with fiberglass and use a cooler on the return line, save a few pounds in the process. Just how much heat is picked up in the fuel on the return?  The Mazda fuel pump assembly has the return going in a few inches from the pick-up for the pump and I suppose there are no fuel heat related problems on the car.

You talk about a boost pump.  What type and how is it plumbed in to the fuel system? (Maybe you get the idea I like to copy from successful people?)

 

Wendell

Fuel system design is certainly a critical area and a lot of thought needs to be given it.

 

I went against the concept of large header tanks and have one that holds approx  32 oz or one pint.  I have it mounted on the engine side of FW (would change that) and at the lowest point.  After my pressure regulator, my return fuel dumps into this tiny header tank. 

 

Many of today's EFI automobiles now use a "returnless" fuel system by controlling the fuel pressure as needed to prevent vapor lock.  I view my tiny header as sort of an in-between a header than and no header tank {:>).

 

I do have blast tubes of cooling air going to it and I did have fuel percolation on the ground before putting the tubes in.  However, the boost pump (6 psi) immediately squished any that occurred.  Having been flying with it in the sunny South for almost 10 years.

 

My rational was that IF your larger header tanks does get filled with hot fuel, its going to take a long time to burn that hot fuel off and get new cooler fuel.  My pint gets replenished at flight power settings so quickly that heat is not an issue.  A long idle on a hot day could cause some percolation, but since I always take off with boost pump on, its never been an issue.

 

Be oh-so-careful in design of your fuel system - needless to say, but will anyhow.

 

Ed

----- Original Message -----

From: Wendell Voto

To: Rotary motors in aircraft

Sent: Saturday, August 25, 2007 9:59 PM

Subject: [FlyRotary] Re: need help

 

Thanks Ed and Charlie,

You both got the same answer, I think the 1.8 gal. estimate came from my first mock-up and it was 14 in. instead of 15. In some of my calculations  I did get 2.0 +something as an answer.  Now how much sump tank volume is really needed?  I think Perry Mick uses one slightly over a gallon.  If one gallon is sufficient, then I can save 6 pounds of usually unused fuel.

 

I regret hearing about George Graham, I was hoping to meet him, he sent a drawing of his cooling set-up and was always ready to help.

 

Wendell

 

You can look at your tank as composed of two boxes (actually one and 1/2 boxes).  1st box is  3.75" x 6" x 15" = 337.5 cubic inches.

 

A second box is 3.75 " x (11-6)" x 15" = 281.25 Cubic inches but you really only have 1/2 of this box,   so triangular section volume  = 1/2 (rectangular section) volume  = 281.25 * 1/2 = 140.625 cubic inches

 

So total volume = volume of 1st box (337.5 )+ 1/2 volume of second box (140.625) = 478.125 cubic inches or 2.07 US Gallons

 

Ed

----- Original Message -----

From: Wendell Voto

To: Rotary motors in aircraft

Sent: Saturday, August 25, 2007 1:19 PM

Subject: [FlyRotary] Re: need help

 

 

Thanks for the responses to my requests.

 I wasn't to go John Slade's route and try to put in an air conditioner and the lines need to take 250 to 300 psi.  The larger return line should only see about 175 psi on a hot tarmac (engine off) and the feed line will see up to 275 psi (assuming a inefficient condenser) on a hot day.

Finding a place for the condenser is the main problem as I see it.

 

I'll look up Mazdatrix for the exhaust studs.  I hoped someone knew the exact size so they could be purchased locally.

 

Here is a math problem for you brain types (all rotary head but me) -how much fuel will a tank hold that is 3.75 in. tall, 15 in. long, 11 in.deep on the bottom, top is 6 in. deep then slopes to zero at the front? I think it is about 1.8 gal.

___6in._

|                \  

|_________\

       11in.

 

Wendell

 

In a message dated 8/23/2007 8:29:10 PM Pacific Standard Time, jwvoto@itlnet.net writes:

Hey guys,

I still need help in obtaining the nuts for the exhaust studs on the 13b. Also, does anyone have working phi ratings for 3003-0 aluminum tubing.  Can it withstand 250psi

Wendell

What wall thickness Wendell? .010 thick NO! 1 inch (wall) yes. Give us an idea of what you are using it for.

Bill Jepson

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