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Looking at installing a larger engine

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Looking at installing a larger engine

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Old 10-10-2018, 03:28 PM
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Steve Collins
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Default Looking at installing a larger engine

I have been considering moving up from a 160N class engine to a 180N in my Fei Bao Dolphin. Will I need to convert my fuel tanks and plumbing to “high flow” fittings and plumbing?

Whether your answer is yes or no, please elaborate as to why or why not.
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Old 10-10-2018, 05:04 PM
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Len Todd
 
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Depends on the brand and the fuel line setup (e.g. Dirk told me that the 4mm line was good for Kingtech up to 200. So I am using standard fittings on the K160 which draws thru two tanks and a UAT. But my Jetcat 140 would not draw enough fuel thru the UAT, main tank and saddles w/o going to large fittings, lines and clunks. The JC had 6 mm line from the pump. The KT has 4mm line from the pump.
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Old 10-10-2018, 07:09 PM
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Looking at the Kingtech 180 as a replacement.

I have been running a Jetcat older Titan (propane start) which is 4mm tubing from the pump to the engine. I currently have a P-160 SX kerostart installed with the same setup but this is a new install that has not been run yet.
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Old 10-10-2018, 07:18 PM
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Originally Posted by Steve Collins View Post
Looking at the Kingtech 180 as a replacement.

I have been running a Jetcat older Titan (propane start) which is 4mm tubing from the pump to the engine. I currently have a P-160 SX kerostart installed with the same setup but this is a new install that has not been run yet.
Been running a k180 with a 6mm line from the tank to the pump (with some restrictions, such as the clunk line which contains a 4mm brass tube for a few cm) and 4mm line from the pump to the engine (with no further restrictions) for 5 years over 3 different models and setups
Never had a flameout or any hint of a problem.
In one plane for a time I even had 3 fuel tanks in series, each one containing a 4mm brass tube clunk line, and a single 4 mm brass tube as a vent. I do not use BVM UATs though, only DIY hard plastic bottles (also made with 4 mm brass tubes).
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Old 10-11-2018, 06:29 AM
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Len Todd
 
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With some of the newer turbines having the fuel pump in the turbine, the optimum fuel line configuration is different. The P-140 has the pump in the turbine and would not spool up to full power w/o high-flow fittings, UAT, clunks and lines. I also went with larger tubing in the tank's stopper. Kind of makes sense seeing how they put a 6mm fitting on the turbine. The hi-flow setup not only allowed full power, but I also added a huge hopper tank in the fuse. The typical hi-flow BVM type UAT's outlet is 8 mm versus the normal UAT''s 6 mm outlet. I used 3/16" tygon to the UAT and 8 mm line out of the UAT. I converted down to 6 mm just before the turbine. These several changes solved the spool up problem and short 6 minute flights. I have the Ultra Flashes' main, two saddles and a large hopper for tanks.

The K-160 has an external pump that makes a conversion from 6mm to 4mm at the pump. So the inlet side was set up with 6 mm lines, hi-flow clunk, larger tubing in the fuel tank stopper, normal UAT, 6 mm fittings to the pump. Then it is 4mm from the pump to the filter to the turbine. I used the T-One's smoke tank in series with the main tank for added fuel. I now can get 10 + minutes flights on the K-160. The hi-flow clunk was only used because that is what I had laying around.

Point being, if the pump is internal, the fuel system setup may need to be different. Also, the smallest passageway in the fuel system is the biggest constraint. Add a second constraint and the effect is even larger. There is a flow differential at every constraint. And lastly, for fluids it is harder to suck/draw than it is to push fluid out the outlet. The harder the system draws fluid, the more likely that future air in-leakage may occur. We are stuck having to draw fuel to the pump thru our tanks. At some point, the restrictions in the inlet side may limit fuel flow as I experienced with the Ultra Flash. So why not minimize the effort it takes to get fuel to the pump?
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