Does it make any difference?......
 

Guys,

If you have a fuel tank with 4mm festo fittings and you run about 5mm of 4mm tube before stepping tubing up to 6mm does that help improve flow or not??

Is the fact that you have a 4mm fitting anywhere in the system mean you are restricted full stop? I would imagine it has to help a bit? Maybe a half way step to a full large bore setup?

I have a couple of models in which I am moving up from a 160SX to a 180RX. I've run regular large bore tygon (not the 3/16" stuff just large bore) on both 160 setups with no problems but as the 180 may just start pulling that bit more I wondered if upping from 4mm straight to 6mm would help. If I were going to a 200 then I'd change everything for the large 3/16" bore JMP/Festo fittings but I'm trying to avoid the hassle and cost of all that whilst trying to help a bit.

What do all you fluid mechanic experts say?.........

RE: Does it make any difference?......
 

there is no doubt that it will cause some restriction in the fuel flow, but as it is a fixed value, your pump would adjust for it...I think....

Another consideration, is that it will also be a restriction when you are refueling as well.....

RE: Does it make any difference?......
 

Marc

Why not do some research and let us have the findings.

If you start with a simple tank and 6mm tubing, and make sure the 180 will reach full power. Then try introducing say 1 ft length of thinner tube to the suction side. If you restrict the flow a lot you will see a stream of bubbles from the pump cavitating and the engine will not reach full power. You should find that the length of the thinner pipe will make a difference as well. If you want to do a very simple check you can fit a valve and gradually shut it with the engine at fill power.

You could repeat the exercise on the outflow side of the pump, which you will find is not as critical as the suction side. (I think Wren run 3mm pipe on the outflow of their 160). The air vent will not have a big impact either.

John

RE: Does it make any difference?......
 

Hi guys,

Always an interesting debate. However a rather simple answer - check the size of the nipples on your pump, then fit tubing with the same size......

.....it has worked for me with all my turbines and I have run from 5 to 25 kgs thrust.

Cheers,

JanR

RE: Does it make any difference?......
 

One thing that is forgot about and touched on above, is the barb nipples on the pump, The barbs are designed to be used with 4mm festo tube and also 6mm tygon provided you wire lock it.

The same pump is supplied for the P60 to the P200, so why does the pump on 120+ size turbine, come with the same size barb fitting if you need a bigger pipe on the inlet?
Many people on bigger turbines like to use 6mm festo pipe or larger bore tygon, as it seems to be preferred to allow the pump to suck sufficent fuel, then the pump really should have a barb to suit the larger pipe, not a barb fitting for 4mm pipe.

But again as Jetcat supply a pump for the P200 turbine with small 4mm size barb fittings would that not suggest that 4mm pipe should be used and what they recomend? if not, then obviously you would think, fit bigger fittings on the pumps.

RE: Does it make any difference?......
 

Yes, it does. No restiction is good in the suction side plumbing. IMO for turbines over 100N it should be at least 6mm everywhere. It may work in some conditions but it will come back and bite you at some point.

PaulD