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prkaye

Well Known Member
I am placing my Red Cube Fuel Flow sensor between the mechanical fuel pump and the carb. Unfortunately, the geometry is going require an AN822 fitting at the inlet of the Red Cube.
1) Is a 90 degree fitting here OK?
2) Should I use aluminum or steel fittings in the fuel flow sensor?
 
Phil,
I asked Dave Campbell of EI the same question on whether steel or alum fittings should be used and he said either was fine but to steer clear of stainless steel as they had problems getting the SS fittings to seal. As the fuel hose fittings tend to be steel, that's what I'm going to use when the time comes.

As to the use of a 90-deg fitting, I think it wouldn't be an issue.
 
Phil,

I spoke to EI about this too (though my Red Cube is going between my fuel servo and fuel divider).

Here is what I was told:

Brass fittings are the first choice, then steel, then aluminum.

In all cases we assume flex line in and out of the transducer and some sort of thread sealant/lubricant. The length of flex does not need to be 5 inches- it could be less.

You can use 45 and 90 degree fittings in both the in and out ports of the transducer. We would prefer that a 90 not be used in the in port, but our tests show that it is not really a factor in the flow indication. If you have to make a 90 degree turn, maybe a 45 in and 45 out?

Regards,
Steve Hutt
RV-7
West Sussex, UK
 
Thanks guys, that's good to know. I really do have to use 90 degrees on the inlet (and 45 on the outlet) because the only place I left for the transducer means the fuel pump is on the outlet side of the transducer, so the hose has to go over and down to the inlet port on the far side. Vans' VA-129 hoses turn out to be about the right length for both hoses.
 
question on other location(s)

I do not wish to hijack this thread but I have a question concerning the location of mounting these red cube fuel flow transducers. I am not mounting my cube in the engine compartment. I have mounted mine on the cockpit side of the firewall in line after the electric boost pump and before the mechanical fuel pump. Does anyone see this as a problem?
 
Just note that the documentation says the hose coming out of the outlet shoud not go downhill afterwards (to avoid trapped bubbles). I'm not sure if this means it shouldn't go downwards immediately after, or it shouldn't go down at any point after the outlet.
In my case, I mounted mine on hte firewall (engine side), very low so the outlet is at about the same level as the carb inlet.
 
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