[rv8ch]

gascolator vs. filters

A gascolator IS a water separator AND a filter........Why are you re-inventing the wheel??????

See Wade's response above. It's right on target.

Your diagram is beautiful, but I don't see any check valves........what keeps the pumps from backflowing during one pump operation?????

Thanks! The fuel pumps have built-in check valves.

 

[rv8ch]

fuel filters

That looks good, but I would have put the fuel filters before the fuel selector valve. I guess there are pros and cons to each method.

True. I'm counting on the pickup screen to keep any big chunks out of the fuel selector valve. My thinking is that having two filters after the valve allows more redundancy, since a clogged filter does not render a whole tank unusable.

 

[jonbakerok]

On an RV8 or other taildragger, aren't the wing sumps the low points, so won't any water will collect there? [/IMG]

What if you're parked on a hill?

 

[sadams]

Interesting discussion, but what are the advantages of using a plain filter over a filter/water seperator (gascolator)? Vapor lock problems seem to be more an issue of location of the gascolator than the gascolator itself. Leaking seals in the gascolator are an issue of maintenance, not the gascolator itself. Adding complexity by including multiple filters in the system in my opinion just adds additional points of failure rather than decreasing the risk from that of a gascolator single point of failure. Saying that you have never found significant amounts of water in your system at preflight, so it's not an issue to worry about is the same mentality that some pilots use for rationalizing not doing a good preflight on every flight. i.e. I never find anything, and it just flew fine yesterday, so a preflight is really a waste of time. I'm all for advancing aviation technology and improving safety and efficiency of our aircraft, but using a filter than can clog, swell with water contamination, does not provide any protection from water contamination, is not easy to inspect or service with every pre-flight, etc does not in any way seem like any kind of improvement. It's like saying the round wheel is pre-historic technology and putting triangular tires on your plane just because you can. Anyway, that's just my relatively uninformed opinion.

 

[rv8ch]

Interesting discussion, but what are the advantages of using a plain filter over a filter/water seperator (gascolator)? ...

If the gascolator gets stuck open, it can let in air, or leak fuel.

There are no gascolators that I could find that filter down to 10 micron, which is what the fuel injection systems need on the high pressure side.

For my installation, it was not convenient to have a gascolator installed where it could be both a low point in the system, and plumbed on the low pressure side.

If I were installing a carb, with it's low flow rates, low pressures, and loose filtering requirements, I'd probably install a gascolator. With FI, you need good filtering, it runs at high pressures, and flows a lot of fuel. I could have probably gotten by with only one filter between the pumps and the fuel rail, but I felt better having a large, high flow rate filter between the tanks and the pumps. I also want redundancy through as much of the fuel system as possible. I don't have an engine driven fuel pump, just two electric pumps.

Clearly it's more complex, and that's just one of the negatives of having an auto conversion. I'm not too sure a FI Lycoming has very different requirements, but most people don't install as much stuff as I have.

 

[rv8ch]

sump low point

What if you're parked on a hill?

It would have to be a pretty steep hill to make the wing sump points not be the low point of the fuel system. The angle of a TD is pretty steep.

 

[sadams]

Clearly it's more complex, and that's just one of the negatives of having an auto conversion. I'm not too sure a FI Lycoming has very different requirements, but most people don't install as much stuff as I have.

Thanks for a rundown of the pros of a filter. I only have experience with carburated engines and it looks like FI is a bit trickier, more complex, and not so straitforward in regards to the use of a gascolator.

 

[Norman CYYJ]

In Canada we have no choice. We must install a gascolator or else the aircraft will not pass the inspection. They do work as they are suppose to.

Norman