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EFI fuel line routing...

rmartingt

Well Known Member
I posted about this in my build thread but in hindsight I don't expect it's going to get a whole lot of traffic there, so I'll repost this portion here.

As I'm using EFI my fuel lines just need to go to the top of the engine; they don't need to run down to the intake first. I'd like to keep the lines away from the exit air and exhaust pipes, so I was thinking I could run them up on the back side of the firewall first and have the supply line exit on one side and the return on the other; hoses could follow the engine mount up to the back of the engine and then to the distribution manifold.

I had a whole bunch of 1/4 3003 tubing laying around with no specific use for it, so I decided to mock up a line (visible below) and use it as a template. The final line would probably be stainless 3/8. I think I can keep it tight enough to the firewall that the rudder pedals won't hit it even at full deflection and fully forward mounting. Return lines would basically mirror this on the left side.

The routing in the picture behind the firewall shows about what I'm thinking, though I think I'd have the exit come an inch or two further outboard (where the small sharpie circle is upper right; the one below the angle extrusion is where the brake reservoir penetration is per b/p) to avoid the brake reservoir if I decide to stick with that location. The bottom picture shows the proposed exit location from that side; a bulkhead. Line supports would be little brackets with P-clamps, screw tab facing aft. Thoughts welcome.

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Some random thoughts in no particular order:

The closer you keep the plumbing to the "typical" RV, the less rework you will have to do down the road.

EFI is essentially unaffected by heat, so moving the exit points up the firewall on that basis doesn't pass the giggle test.

I'm doing a bunch of wiring cleanup in the exact areas you are running your fuel line. Having fuel and electrical in such close proximity (in the cabin) makes my palms sweat just thinking about it.

I think you are familiar with my fuel pump block off plate/fuel hose bracket on my Rocket- I can recommend that as a good clean way to transition to flex lines off the firewall to hard lines (or hose) up the accy case to the top of the engine. With no mags or fuel pump there is plenty of room.
 
Mike is right about that vertical having some heavy wiring routing there. Also, you will likely want a steel bulkhead fitting(s) for the passthrough, and a doubler there too. Eventually, you will be on your back working up in there for something - - mark my words. It would not be good to look up at some fuel fittings and be working on then where you can not escape.

Its easy to present issues, and hard to find solutions. The other installed stuff that is relatively standard can get in the way of a good plan, so you might want to think about all the other stuff and it's routing then get a good work-around for these fuel lines. Coming through the firewall, then vertical can still present come challenges, but likely fewer than up the inside. You will just want to get around the heater box.

You might be able to route some fuel lines out the back of the baffling and tightly down the engine (avoiding the ignition wires) to cross to the FW below the oil filter. It would leave a clean space for the oil changes. The lower right of the engine has a governor, and battery on the FW. Heavy wire, tubing etc, favoring the left.

BTW - "Lines" are assumed to be metal. Stainless can be mounted to the engine and be less prone to fatigue from case vibration.

Sorry, no real answers for you, just thinking out loud.
 
Just sayin"

we typically use the stock hole for supply and a 'mirrored" hole for the return after the regulator. With the SDS system, the fuel block can be mounted on the center of the engine case, so supply and return hoses arent an issue. Ross uses -3 hoses for the injector lines, BUT someone with sufficient skills could do them from rigid stainless--mimic Lycomings.

Michael and Bill make a great point about wiring near where you have the tubes proposed----think separation. The SDS pump and push alot of fuel under higher pressure---not a fun sight, so things need to be better than close enough.

Tom
 
Some random thoughts in no particular order:

The closer you keep the plumbing to the "typical" RV, the less rework you will have to do down the road.
Same story with anything different...

EFI is essentially unaffected by heat, so moving the exit points up the firewall on that basis doesn't pass the giggle test.
My thinking was not about heat affecting EFI under normal function, but more in fire scenarios and just heat degredation of the hoses. But I'm thinking now that maybe my impression of where the exhaust pipes and cooling air run, and where the "standard" fuel lines run, maybe aren't as close together as I'd thought.


I'm doing a bunch of wiring cleanup in the exact areas you are running your fuel line. Having fuel and electrical in such close proximity (in the cabin) makes my palms sweat just thinking about it.
And here I was thinking the wiring would be more towards the center and higher up.

I think you are familiar with my fuel pump block off plate/fuel hose bracket on my Rocket- I can recommend that as a good clean way to transition to flex lines off the firewall to hard lines (or hose) up the accy case to the top of the engine. With no mags or fuel pump there is plenty of room.
Found it over on HBA... if the back of an O-360 is anything similar, yeah, looks like decent room. I'd planned on using the coil mounts that go on the magneto hole covers though, so some slight changes might be in order.

There seems to be a dearth of good pictures of EFI installations from behind/underneath the engine. Seems everyone wants to show off the lines to the injectors and their coil pack/ignition wiring setup.


Mike is right about that vertical having some heavy wiring routing there. Also, you will likely want a steel bulkhead fitting(s) for the passthrough, and a doubler there too. Eventually, you will be on your back working up in there for something - - mark my words. It would not be good to look up at some fuel fittings and be working on then where you can not escape.
Again, good to know about the wiring locations. Bulkhead fittings will be steel, of course; firesleeved braided hose firewall to engine; hose or stainless on the engine.

Its easy to present issues, and hard to find solutions. The other installed stuff that is relatively standard can get in the way of a good plan, so you might want to think about all the other stuff and it's routing then get a good work-around for these fuel lines. Coming through the firewall, then vertical can still present come challenges, but likely fewer than up the inside. You will just want to get around the heater box.
I'm not that familiar with how "the standard stuff" gets installed, really, and I don't have a lot of good examples around to go look at. I also have a hard time visualizing what's not there and fabricating stuff up without drawings to work from. There's a reason I did my fuel selector install (see build thread) in Catia first...

You might be able to route some fuel lines out the back of the baffling and tightly down the engine (avoiding the ignition wires) to cross to the FW below the oil filter. It would leave a clean space for the oil changes. The lower right of the engine has a governor, and battery on the FW. Heavy wire, tubing etc, favoring the left.
Well, two batteries here... but I'll look at it. Right now I like Mike's fuel pump cover bracket.

we typically use the stock hole for supply and a 'mirrored" hole for the return after the regulator. With the SDS system, the fuel block can be mounted on the center of the engine case, so supply and return hoses arent an issue. Ross uses -3 hoses for the injector lines, BUT someone with sufficient skills could do them from rigid stainless--mimic Lycomings.

Michael and Bill make a great point about wiring near where you have the tubes proposed----think separation. The SDS pump and push alot of fuel under higher pressure---not a fun sight, so things need to be better than close enough.

Again, I didn't know lots of wiring usually went through there. I figured the lines could go in first and I'd run the wires as necessary for separation.

Tom, if you fancy a ride down to Pooler one day I'll buy your lunch. We might also be up in Ridgeland sometime in the next couple weeks if you have some examples or know of anyone with one of these setups around here...
 
Concerning heat/fire issues with the conventional hose placement - the hoses are most certainly going to have firesleeve protection, so that takes case of the IR off the pipes which is going to be the primary heat issue. The hoses can certainly live with the modest cowl outflow temps.

As for fire, well, since we both run EFI we need to be prepared to shut the engine down at the first sign of flames. Fire will quickly take out wiring, sensors and other fragile bits anyway, so we shouldn't count on managing a fire with the engine still running. A firesleved hose is one of the least of my worries in a piston engine fire.
 
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