Facet Cubes vs. Cylinders

[Wrsteinesq]

Other than 'this is the way we've always done it,' is there a good reason why we stay with the Facet cylinder pump (477-060E) rather than the solid state cube pumps Facet offers? I'm thinking specifically about No. 40171. My present cylinder is physically obstructing my throttle cable, and rather than do a work-around, I thought the smaller and cheaper cube might solve the problem. Any thoughts/reactions? Thanks! Warren Stein

[ndutton]

Looks like you're good Warren. Pressure and volume specs for the 40171 are where they should be for our application and most importantly there is this from Facet/Purolator:
Facet®/Purolator® fuel pumps meet Coast Guard Ignition Protection Test Requirements 33CFR183.410 and Fire and Thermo Shock Test Requirements 33CFR183.590
33CFR is USCG requirements

[Wrsteinesq]

Thank you, Neil. I am aware that the cylinders contain a filter and I don't think the cubes do; but I've got the Racor AND I will install a polishing filter, so I can't see what amounts to a third filter as a necessity.

Also, the cube has both a check valve and a positive shut-off valve. Of course we all should and probably almost always DO shut off the petcock when leaving the boat, BUT humans still mess up; and I can't see how having what amounts to an automatic shut-off is anything but good. In the simplicity-vs-safety debate, my inclination is safety, unless someone convinces me that positive shut-off valves and/or check valves are fairly likely to cause problems. Does anybody think that?

[ndutton]

I wouldn't put much stock in the cylinder pump filter. It's about as fine as a BBQ grate. If you have particles big enough for the filter you have much bigger problems.

[Wrsteinesq]

In shopping the cubes, I see that one vendor (Aircraft Spruce) offers both the 40171 and the 40178, while Pegasus only seems to offer the 40178. The only difference seems to be that 40171 specs 12" minimum lift, while the 40178 specs 36" minimum lift.

What is "minimum lift" and which is the better choice for our A4 application (assuming mounting the fuel pump on the usual bracket, not on the bulkhead)? Or it the real 'work-around' for my throttle cable interference problem, to do just that: mount the pump on a bulkhead? If so, what are the optimum considerations? And which model should I choose: 12" minimum lift or 36"? The price difference is negligible.

[ndutton]

Most boat fuel tanks are at the same level as the engine or nearly so therefore lift specs aren't all that important. I have my pump bulkhead mounted as does roadnsky Jerry and no doubt many others without issues. Two things to remember with bulkhead mounted pumps: you'll have to provide a case ground for it to work and it's a USCG requirement to be mounted within 12" of the engine.

[joe_db]

IMHO the newer Facet/Purolator cube pumps are likely as good or better than the old cylinder pumps. They do need a filter of some kind, but we all have them anyway.
This page lists all the versions:
http://www.facet-purolator.com/cube-fuel-pumps.php
40171 Cube 12 3.5 - 2.0 15 PACKARD Ring 1/8 - 27 INT 12" Y Y
2-3.5 PSI is right on for our engines. The positive shut-off is a good safety feature too. I have two fuel pumps, one runs about 2 PSI and one runs about 4 PSI. I can tell absolutely no difference in engine performance between 2 and 4. I wouldn't go much past 4 though, our carbs don't need a lot of fuel pressure.

[Peter]

I note that the maximum operating temp. for the cube pump is 140 F while for the cylinder it is 180 F

Anybody have any idea if this is a concern?

Peter

[joe_db]

I doubt it. My pump is cooler than the ambient air when running, the fuel itself cools it. These pumps get used in all kinds of vehicles that are not necessarily very cool.

[BunnyPlanet169]

Originally Posted by ndutton

Most boat fuel tanks are at the same level as the engine or nearly so therefore lift specs aren't all that important. I have my pump bulkhead mounted as does roadnsky Jerry and no doubt many others without issues. Two things to remember with bulkhead mounted pumps: you'll have to provide a case ground for it to work and it's a USCG requirement to be mounted within 12" of the engine.

Note the cubes are two wire, not case ground.

All other specs and construction look identical with the exception of filter, which as has been mentioned is really coarse at 76 microns. I would guess the cost savings are the lack of filter and disassembly option.

[ndutton]

Originally Posted by BunnyPlanet169

Note the cubes are two wire, not case ground.

Roger that. I understood, perhaps mistakenly, that Warren was considering relocating his existing cylinder pump rather than replacing it with a cube.

[Wrsteinesq]

Neil, I'm sorry if that wasn't clear. I do indeed intend to replace my cylinder pump. My thought was, that replacing it with a cube pump might be as effective, perhaps better, and cheaper to boot. After your comment this morning, I did go ahead and order one of the cube pumps. It was not exactly the model we were discussing, but the model with 36 inch minimum pumping height (or whatever that phrase was). In all other respects it was identical. I could not see where having additional pumping lift was of any detriment. Anyway, I will be moving it to a bulkhead rather than mounting it on the block. That should give me a nice shiny new pump, and get rid of my problem of throttle cable interference.

[ndutton]

No worries Warren, whatever works . . . . and is compliant with safety standards.

[roadnsky]

Originally Posted by Peter

I note that the maximum operating temp. for the cube pump is 140 F while for the cylinder it is 180 F

Anybody have any idea if this is a concern?

I do...

A few years back I discovered my pump ran pretty hot during the summer months specifically while at idle RPM's.
I think I remember the temps averaging around 120-130°
I did all sorts of testing and measuring and we didn't really come up with a proven reason for the higher temp other than my engine room environment in the summer is about 110-120°
(I sail in a desert lake)

I don't have the time at the moment to find the thread but if you search hot and facet I think it'd pop up pretty easily.

I do remember a few others on the forum reporting "high" temps too but unless you sail in a hot environment, I don't believe the lower cube temp is of much concern.