Gascolator to firewall - fuel line

[DBeaulieu]

Looks like there is no getting around having a couple of 90 degree bends to bring the fuel from gascolator to firewall penetration...at least the way I have mounted the gascolator to the fuel selector valve. Additionally, I seem to have an interference issue with that line running forward and crossing paths with the short line from the aft/fore fuel lines junction that feed the fuel valve. One of those lines will have to be below the other. Any thoughts, suggestions, "don't worry about it" - please comment if so! Thanks...

Dave (from Maine)

aft outlet.jpg

[David Swartzendruber]

I'm eliminating the 90 deg fitting at the back of the gascolator by adding a new exit port out the side of the gascolator. The rear port will be plugged.

[DBeaulieu]

David Swartzendruber I like that idea, would seem to make an easier flow route but not sure what that entails and if you have Bob's gascolator. I assume drilling and tap of a new port, or welding in a new bung?

[David Swartzendruber]

I do have Bob's gascolator. You are right that It involves drilling and tapping a new port. A complication is that there is already a blind threaded 1/4-20 mounting hole in that 3 o'clock position where the new port will be. I had both mounting holes welded up by a professional welder and will put new mounting holes at the 4:30 and 7:30 position.

[Bcone1381]

Plan your firewall penetration using a bulkhead fitting. I'm fuel injected with an engine driven fuel pump, and so I put mine on the lower right corner right of the firewall just outboard of the tunnel. (I suspect a carburator might like a left firewall exit, but I don't know for sure) My goal is alll plumbing beyond my gascolator was below the floor. By placing the bulkhead fitting outboard on the firewall gives more space to negotiate the conflicting fuel lines inbound to your fuel selector.

Sooo...I'm viewing this from just below the floor and below the front seat. I see a line exiting the gascolator using an AN822 90 elbow fitting. It then makes a 90 degree bend so that it then travels away from me towards your bulkhead fitting. I adjust the AN822 90 degree elbow fitting at the gascolator so the forward run misses all other lines and penetrates a fuselage former at the aft end of the tunnel.

Here are some shots of my install. The pink arrows May help you see my description.

Screenshot 2024-07-27 at 12.04.59 PM.png Screenshot 2024-07-27 at 12.04.43 PM.png

[Bcone1381]

One more thing....The text below assumes you are using a Carburetor.

A goal is to keep fuel cool. A common item in a fuel system is a fuel flow sensor, for a carb its common to use a "Gold Cube". There is a benefit to Place the Gold Cube on this line prior to the firewall where its cooler. The temperature of the cube transmits to the fuel, and we want fuel to stay cool.

(Rules of Cube Placement change for FI due to pumps)

[DBeaulieu]

Bcone1381 Hey Brooks, I'll be using the EFII fuel boost pump module mounted on the engine side firewall for my engine (YIO-360). I may want to change the mesh in the gascolator for coarse filtration prior to the pump module. Red cube has to go downstream of the pump last I knew. So I'm thinking a 45 fitting out of the gascolator with a large radius sweeping bend hardline to bulkhead fitting on the firewall penetration similar to your posted pic is certainly a solution. I like what David Swartzendruber has planned for his gascolator, but not sure I want to go through the effort to modifiy with another outlet on the gascolator.

[Pbruce]

I put a 45 degree fitting exiting the back of the gas collator. I’m going carbureted with a gold cube. I think it’s ideally supposed to be suspended inline by a flexible fuel line (braided steel, I guess),a minimum of seven inches before a hard mounting point like a firewall penetration. Not advising anyone else to do this, but it does seem like it will be fairly easy to route the fuel line under the floor to the firewall this way, while observing the guidance to “soft-mount” the gold cube. I anticipate using some kind of flexible straps to hold the transducer and the braided fuel tubing clear of structure or other hardware as needed.

[DBeaulieu]

Pbruce ...I've only used the Red cube but the guidance I recall was for a solid vibration free mount (not on the engine) with an upright, mostly level orientation. Does the Gold cube have similar instructions? Not sure what you mean by "soft-mount" - mainly curious...

[Pbruce]

Yes exactly. I don’t have it with me now, but I recall the instruction was to mount it level with at least seven inches of flexible tubing between the gold cube and the next downstream hard tubing. I saw that and decided to have flexible tubing between the gascollator and the cube as well. I expect to mount the cube in a level stretch of braided hose like an inline filter on my lawnmower. I’ll attach it to structure via flexible stretchy straps of some kind so it doesn’t touch anything else. That’s what I meant by “soft mounting”.

[Battson]

I went through the same worries, in hindsight I would say don't worry about the fact it there are "sumps" in the system.

I have the same kind of plumbing conundrum. In the last decade / 1,100 hours of operation, it's caused exactly zero issues or worries.

You do have to be careful about fuel lines moving as everything "settles" once you start flying, anywhere a fuel line could rub against any other part - including the tunnel or boot cowl - you need protective rubber or plastic covers over the line, ideally with some red RTV for good measure (AKA anti-chaffing compound ).

If you are focused on flow rate, I think the only time it matters is with a constricted system with too many fittings, then a flow rate problem can occur and this has happened a bunch of times for different builders. Typically with an O-540 carb engine, with a lot of extra fittings and trimmings, fuel filter, flow transducer, pump, etc in the line causing pressure losses which reduces flow rate. Otherwise I don't think it's a problem, especially if you stick with Bob's fuel system design per the "Bearhawk Book" or whatever might have replaced that guidance.

If you are going fuel transducer, you can leave out the flexible line if you like. It doesn't seem to cause any issues, I know several aircraft which have them in line with hard-lines only. Sometimes people do have issues with occasional high readings, intermittently, but I don't know of anyone who's found that flexible tubing resolves that issue.