mr_matt

My Feedback: (10)

Hi everyone,

What are your guys experience with installs with long fuel pressure lines (say over 24 inches long)? This is the line from the pump to the turbine.

I have previously run one install with the pressure line from the pump to the turbine about 24 inches long. I have done one on a UAV that was over 60 inches long. Both ran fine but neither install was used for that many flights.

I am somewhat worried that a very long tube would introduce some lag to the turbine response that could confuse the ECU and make for bad turbine responce or at worse some sort of oscillation and shutdown. If anything, I would think this long line would dampen response (I think some small turbines like a P-20 even have a minimum length for this line to dampen the pump/turbine response).

Anyway, let me know your experience, the turbine is a JetCat P-200 with a version 6 ECU is that makes any difference.

Regards,

olnico

Hello Matt.
What is sure is that you'd rather have the pressure line than the suction line extended to avoid cavitation.

http://www.ultimate-jets.net/blogs/f...ing-cavitation

Fuel can be considered as non-compressible at the pressures our fuel pumps operate at.
So basically an increase of pump pressure will transmit to the engine port quasi immediately. That is pretty much at the speed of sound in kerosene or 1300 km/s rounded up. For a 3 meter long line ( ie 10 feet ) this is 2 thousands of a second to transmit flow/ pressure increase. Way faster than the V6 ECU computation frequency ( 2 kHz vs 50 Hz ).

However, this is considering a perfect fuel line: ie completely non expandable. In practice, it will all depend on the quality of your fuel lie downstream the pump.
What I can tell you is that I have had perfectly fine results with the black anti static Festo line. It is a lot harder that the regular PU lines but make sure you make large turn radii as it pinches easily!
Also this will help you significantly in sorting out the static electricity shut down that Jetcat ECUs are prone to.

ddennison

My Feedback: (15)

No trouble w my A10. Length was at least 5 feet pump to turbine (Jetcat).

CraigG

My Feedback: (40)

+1

melvin

My Feedback: (3)

Just from a logical view point i would think it would work just fine except for the fact that it would put more load on the pump since it is pumping a longer line of fuel. This would drag down your battery a little faster and wear your pump out a little faster.Just my opinion- not an engineer or anything!!

George

My Feedback: (57)

Matt,

No issues with > 2' runs for me either. Heck, most Euro installs are more than that. Oli's technical explanation puts it into perspective as well.

Bobneal1

My Feedback: (21)

I had a thrust vectoring Eurosport with the pump mounted on a plate out in the nose and the engine in the tail (rhino) and it worked fine.

AndyAndrews

24" is no problem. Any length though should have quality tubing like Dreamworks. I don't use FESTO. The walls are thinner and I've had that stuff blow out before. (true with fuel and air)

George

My Feedback: (57)

I also forgot to mention that on "longer" runs I run 6mm as far as I can then reduce to 4mm just before the engine. I'm not sure if it makes a huge difference that way, but it gives me 'piece of mind' nonetheless.

Zeeb

My Feedback: (41)

While Oli's description covers one aspect of longer lines I'll give you another that comes from being a retired FireFighter; friction loss. Upgrading the line from a 4mm to a 6mm will make a HUGE difference in the friction loss over your stated distances. Think about what happens when you add another length of hose to your existing garden hose, that's friction loss.

George

My Feedback: (57)

Thanks for the info. Zeeb, but from your description, I'm trying to figure out if my 6mm 'upgrade' is better or not. However, I do get the "adding another length of hose to your existing garden hose" example. You said going from 4 to 6 would make a huge difference, is that a HUGE difference towards the good way? I'm assuming yes, but I have been wrong before.

gooseF22

I have used 5 feet of pressure line with no issue.. the larger issue about placement for me is keeping the Suction line to a minimum length and no restrictions.. which is what will cause the pump to heat, bubbles, and drain the battery faster.. I had that issue in my rookie years ago.. I replaced all suction elements with better/larger and ended problem..

Zeeb

My Feedback: (41)

Yes bigger hose is always better and no, that's NOT a pun.... lol

I don't remember the exact numbers but IIRC by increasing the diameter of the hose/line by 50%, you decrease the friction loss by 75%. If you want to know the exact formulas for water which is heavier than the Jet A, Kerosene or diesel, you can check out this link;

http://fireengineeriq.com/Friction%20Loss.htm

It really is quite amazing what even a small increase in the diameter makes. I even found that out many years ago when trying to make my cars faster. Increasing the exhaust pipes from 2" to 2 1/2" makes a big difference and for our current discussion, air behaves much like any fluid.

Okay, I'll quit rambling and go get some more coffee.....

jofunk

I built a 1/4 scale Panther and mounted the K-170 in the absolute rear of the airplane. The fuel and pump are on the CG, about 40" forward. The pump suction line is About 8" long. The only thing in the suction line is a shut off. I am not using a UAT. The pump is pushing through the filter, solenoid, a slack loop, and down 40" of standard sized line. The engine runs fine, and throttle response is fine. FWIW

Joe

mr_matt

My Feedback: (10)

Thanks for the feedback. Oli kind of spelled it out, I was worried that at some point flexibility of the fuel line would cause a delay in the response, but I guess it is no problem.

Thanks again,