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Seeking Firewall Layout Advice

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upperdeck

Well Known Member
I'm looking for advice on laying out my firewall on my RV7.

I'm installing the full EFII system with an IO360 and vertical induction.

I need to locate two 680 Earthx batteries, two starter solenoids, and hopefully the EFII fuel pump and filters on the forward side of the firewall. I have the Earthx produced battery enclosures and considered cutting off the front of the battery case and adding hinges to allow the batteries to be removed out the front, or at least diagonally up, forwards, and out.

Any suggestions greatly appreciated!
 
Don't put the pumps forward of the firewall! You want them as near to the tanks as you can get them, and away from the heat of the engine, to minimize the possibility of vapor lock etc. And no 90deg fittings before the pumps...
 
If you Google images for this, there is a pic of one set up, two red battery boxes stacked. I did mine with the pumps and filters on the engine side, (recommended by Robert) lower left, with extra custom heat shields on the pumps and filters. I put one Earth X battery in the stock location, and another 20 AH Li ion back up battery on the inside on baggage floor mounted flat. I did a little different set up than the two relays, two start battery setup, one Earth X battery is all I need to start the engine, if it doesn't, I'm not flying that day. I need a 100% fully operational electrical system with my setup.
 
Upperdeck,

I am laying out my battery location as we speak. I am installing the EFII system as well. I put my fuel pumps in the cabin. Just finished plumbing the Andair valve yesterday. All I have left is the decorative cover over the top of the fuel pumps.

Back to the batteries, I am seeing if I can get enough room for a double stack on the firewall right side. My second option would be to put one on the left and the right. I did speak with EarthX about installing on the firewall side and they have no issue with it. I plan to put a TC in with the batteries to monitor their temperatures.

Check out my website link for the fuel pump installation.
 
rmartingt said:
Don't put the pumps forward of the firewall! You want them as near to the tanks as you can get them, and away from the heat of the engine, to minimize the possibility of vapor lock etc. And no 90deg fittings before the pumps...
Click to expand...

Robert of EFII stated it was acceptable to install his fuel pumps on the engine side of the firewall with heat shielding. I like the idea of no high pressure fuel in the cabin.
 
bret said:
If you Google images for this, there is a pic of one set up, two red battery boxes stacked. I did mine with the pumps and filters on the engine side, (recommended by Robert) lower left, with extra custom heat shields on the pumps and filters. I put one Earth X battery in the stock location, and another 20 AH Li ion back up battery on the inside on baggage floor mounted flat. I did a little different set up than the two relays, two start battery setup, one Earth X battery is all I need to start the engine, if it doesn't, I'm not flying that day. I need a 100% fully operational electrical system with my setup.
Click to expand...

Bret, do you have pictures of your fuel pump install? Greatly appreciated!
 
219PB said:
Upperdeck,

I am laying out my battery location as we speak. I am installing the EFII system as well. I put my fuel pumps in the cabin. Just finished plumbing the Andair valve yesterday. All I have left is the decorative cover over the top of the fuel pumps.

Back to the batteries, I am seeing if I can get enough room for a double stack on the firewall right side. My second option would be to put one on the left and the right. I did speak with EarthX about installing on the firewall side and they have no issue with it. I plan to put a TC in with the batteries to monitor their temperatures.

Check out my website link for the fuel pump installation.
Click to expand...

Paul, I would love to see what your battery solution is.
 
upperdeck said:
Robert of EFII stated it was acceptable to install his fuel pumps on the engine side of the firewall with heat shielding. I like the idea of no high pressure fuel in the cabin.
Click to expand...

That's one way to look at it. Another way is that vapor lock is bad. Vapor lock is easy when fuel is hot & being 'sucked on'. Vapor lock is hard (virtually impossible?) when fuel is at 40+ PSI. And a high pressure leak in the engine compartment will go undetected until the cowl is emitting flame, while a high pressure leak in the cockpit will be detected almost instantly.

Different strokes....
 
rv7charlie said:
That's one way to look at it. Another way is that vapor lock is bad. Vapor lock is easy when fuel is hot & being 'sucked on'. Vapor lock is hard (virtually impossible?) when fuel is at 40+ PSI. And a high pressure leak in the engine compartment will go undetected until the cowl is emitting flame, while a high pressure leak in the cockpit will be detected almost instantly.

Different strokes....
Click to expand...

Is vapor lock mitigated by a fuel return line? That was my impression and the EFII system has one. The EFII system runs at 35 psi too.
 
upperdeck said:
Is vapor lock mitigated by a fuel return line? That was my impression and the EFII system has one. The EFII system runs at 35 psi too.
Click to expand...

My set up is returning 45 GPH after the regulator, the fuel trip around the loop from the cold wing tanks to the engine compartment and back to the tanks is a very short time, 15 seconds? I don't think there will be time for heat soak to warm the fuel for potential vapor lock, I have been told that high altitude with auto fuel may have a larger affect then temp on VL.
 
upperdeck said:
Is vapor lock mitigated by a fuel return line? That was my impression and the EFII system has one. The EFII system runs at 35 psi too.
Click to expand...

Opinions vary. My opinion is that the return line is an artifact of the old automotive technique of doing mechanical fuel pressure regulation at the engine fuel distribution block, to ensure that pressure is stable at the engine.

Virtually all current cars use some form of 'dead end' system, with no return line. Pressure might be sensed at the distribution block, but the pump is in the tank, ensuring the entire line is at high pressure (which minimizes the risk of vapor lock). No heated fuel is returned to the system, and any vapor is immediately purged through the injectors themselves. Lines are kept small enough to flush pockets of vapor.

Fuel boils in the old Bendix style fuel distribution lines because they are effectively open to the atmosphere (unpressurized), and sit on top of the hot engine. Not really a factor with automotive electronic injection.

Fuel can also boil on the inlet side of the engine driven fuel pump, on both Bendix injection systems and carburated systems, because (at least in low wing a/c) there's no 'head' feeding the pump, it's *sucking* (lowering the pressure) of the fuel in the source line, and it's *hot* in that area.

If your injection pumps are forward of the firewall, they can heat soak, and any fuel line feeding the pumps can heat soak, and you still have the pumps sucking on the fuel. So the inlet side would see the same potential for problems as the 'traditional' systems.

Of course, the above is just my opinion, based on my research. Do your homework. :)

Charlie
 
bret said:
My set up is returning 45 GPH after the regulator, the fuel trip around the loop from the cold wing tanks to the engine compartment and back to the tanks is a very short time, 15 seconds? I don't think there will be time for heat soak to warm the fuel for potential vapor lock, I have been told that high altitude with auto fuel may have a larger affect then temp on VL.
Click to expand...

Bret,

I have not set my pressure yet. I just want to clarify, your setup is returning 45 GPH or is it set to 45 psi?
 
upperdeck said:
Bret, do you have pictures of your fuel pump install? Greatly appreciated!
Click to expand...

20160222_043719%201_zpstfwmbonn.jpg


20160503_210902%201_zpss5ztkc1o.jpg


The second pic I made a new thicker, longer heat shield and mounted a bracket so I could secure the fuel line going to the engine, also not shown are the heat shields for the pre and post pump filter heat shields now installed. not shown is the post HP filter that mounts on the pump heat shield. love this setup, fires right up and purrs like a kitten at idle 600 RPM.
 
219PB said:
Bret,

I have not set my pressure yet. I just want to clarify, your setup is returning 45 GPH or is it set to 45 psi?
Click to expand...

Pressure was set returning, engine not running at 35 PSI. My flow test was 45 Gallons per Hour.
 
upperdeck said:
Paul, I would love to see what your battery solution is.
Click to expand...

Upperdeck,

One of the reasons that I put the fuel pumps in the cabin is so that I could free up the firewall for the two batteries. This cleans up the wiring and minimizes the number of large gauge wire firewall penetrations.

The other was that if I developed a fuel leak on the firewall side there was a good chance that a fire would develop due to all of the heat sources.
 
219PB said:
Upperdeck,

One of the reasons that I put the fuel pumps in the cabin is so that I could free up the firewall for the two batteries. This cleans up the wiring and minimizes the number of large gauge wire firewall penetrations.

The other was that if I developed a fuel leak on the firewall side there was a good chance that a fire would develop due to all of the heat sources.
Click to expand...

Don't Ja just love this experimental thing! 32.5 ways to skin a cat. On the large cable through firewall thing, I did some different thinking, no battery cables through FW for me. my secondary backup battery inside is not for starting, only comes online by a heavy switch to run parallel 14 G wires to the three redundant separate fuse block to keep the EFII alive and panel stuff if I don't need to load shed, but the secondary back up battery by itself should run the EFII for 2 hours.........KEY word......should :D
 
fuel pump location

The fuel pump can go on the cabin floor or on the firewall.
If you mount it on the firewall, you want to put it low and not too close the exhaust pipes. The fuel pump comes with a heat shield to block radiant heat from the exhaust system. The pumps are self cooled by the 30+gph of cool fuel that runs through them at all times.
Vapor lock is not an issue with our system since we use a full return fuel scheme just like your car. One way fuel systems like mechanical injection or a carburetor can experience vapor lock and have different fuel system layout considerations.

Robert Paisley
 
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