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Old Apr 03, 2012, 09:19 AM
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Earl, I don't care what kind of gas China uses. If the engine is being sold in the world market it needs to work everywhere. Accepting this sort of product only leads to more trash product from the supplier. They could care less, the manufacturer has already sold their product to the distributor and has been paid. The people eating this will be the US importer.

Just how hot is your pump getting? It sure sounds like gasoline boiling in the pump, otherwise you'd have bubbles when the pump is cool as well.

These RCEXL ignition are not grounded to the engine. If you pull the plug lead where is the ground connection to the engine case? The metal plug boot jacket is the ground. You only need to insert the plug in the plug boot and it's grounded, No need to touch it to the ungrounded engine.

Greg
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Old Apr 03, 2012, 09:38 AM
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I bought the engine more for curiosity than anything.

Oh OK good point. I don't know what I was thinking about with the ignition unit ground. You are correct. I just see a lot of folks having car or motorcycle problems and the first thing they do is check the spark and then they tell me how strong it is as they can get a two or three inch long spark off of it easy. I then tell then to go and buy a new ignition coil as they damaged it. It is even worse on the engines that use a COP (coil on plug) system, as the coil usually goes bad instantly when you do that.

The pump isn't getting super hot, you can still touch it. But you can feel the heat it absorbed off the back of the engine where it sits behind the engine. It doesn't take a lot of heat for the gasoline to turn into vapor. Car engines use pressure to keep it liquid, such as what they use with fuel injection systems.

I don't think there are any USA importers for NGH engines yet. The big USA importers tend to do things in their own interests, so it may never be sold directly inside the USA. I doubt anyone will be importing a bunch of them into the USA anytime soon though. Likely for some of the reasons you mentioned.

Saito had a lot of problems at first with their gasoline engines too. Carb and fuel pump problems too. Plus overheating as well. The other gasoline engines had teething problems at first too. They were still selling them to people nonetheless. I don't hear about the carb problems as much as I did a few years ago, so maybe they solved the problems or everyone figured out what not to do and what to do.

NGH appears to be the very first engine company to put into production a small gasoline ignition engine so far. Magnum appears to have faltered and I haven't seen anything about their engine since its announcement a couple of years ago. Fox Manufacturing seems to have stalled on something with theirs too.

So I am willing to cut them some slack in having teething problems in this case. There are a lot of technical issues one has to overcome to get it to work.
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Old Apr 03, 2012, 12:14 PM
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Quote:
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I don't think there are any USA importers for NGH engines yet.
http://www.agaperacingandhobby.com/
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Old Apr 03, 2012, 12:23 PM
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There are a lot of technical issues one has to overcome to get it to work.
Yes but what fun! I know, I'm sick
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Old Apr 03, 2012, 01:48 PM
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Doctor_X thanks for the link, I somehow missed that. I got mine from HiMark in China.

GravityKing, yeah if it works pretty good, I'll fly it. But I was thinking more about the engine designer who had to design and engineer it and get it in production so they could make many of them too.

I am still fascinated and puzzled over why one can't just use a carburetor that looks like our glow carbs but setup for gasoline instead. Everyone seems to go to fuel pumps and carbs designed to use fuel pumps on the gasoline engines.
When you look back to the early days, the engines all had a fixed intake venturi and no throttle as they flew free flight then. But the engines seemed to work just fine like that. Apparently there is some undiscussed technical issue that I don't know about as to why one has to have a more complicated carb and fuel pump setup with a gasoline engine instead of the simple carbs we use on glow engines.
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Old Apr 03, 2012, 02:48 PM
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why one has to have a more complicated carb and fuel pump setup with a gasoline engine instead of the simple carbs we use on glow engines.
because the fuel / air ratio is not the same for both fuels.
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Old Apr 03, 2012, 03:36 PM
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It think it is because the tolerable air/fuel ratio for gasoline is 13.2-15.1:1 while the tolerable air/fuel ratio for methanol is 2.8-13.6:1. At least this what my book "Alcohol Can Be A Gas" says.

So a trying to run gasoline in a non-pumped, glow carb (even with more taper to the needles and what not) would be very finicky. Gasoline has a very narrow flammable window it seems.
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Old Apr 03, 2012, 03:48 PM
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Ok, that makes sense. So no wonder everyone winds up with a complicated fuel delivery system and carb to get it all to work. The old free flight gas engines all had a fixed venturi for full throttle only, so one only needed to get it to work for one engine speed then.
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Old Apr 03, 2012, 04:38 PM
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Next question. If the pump needs a bit of space and venting to help remove the bubbles, is there any need to keep to the 8cm maximum length of hose from pump to carb. why is the length so critical?
more experimenting required, will move pump to new location, might have to be below engine on test bed so it is away from the engine cylinder and exhaust.
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Old Apr 03, 2012, 06:00 PM
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I'd be more worried about the pulse line from the crankcase to the fuel pump. If it's soft enough it can flex in and out enough to not have enough pressure differential and lower the fuel pump pressure. An aluminum tube with a piece of fuel line on each end would work better. As far as pump to carb pressure goes, it should be the same even with an 8 in. line. When I used my outboard test tank to run gas engines mounted on the bracket and the fuel line going down into a 5 gallon gas can on the ground, it had no trouble pumping the aproximate 3 ft. up to the carb.
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Old Apr 03, 2012, 07:01 PM
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Shifted pump

Ok so I have taken the pump off the back of the engine and placed it on the mount. A bit rough but it will serve the purpose.
Ran the engine for five minutes and it was certainly up to temp. pump was cool and showed considerably less bubbles. Will run it again when it is in full sun and around midday. Should be quite warm today around 26c, so a good test.
No idea how I am going to fit this into the plane cowling or even assure sufficient air flow for cooling but after the next test I will then make the fuel tube from pump to carb a bit longer, say 15cm and see what happens.
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Old Apr 03, 2012, 07:27 PM
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I'm not familiar with the pump but there can't be any air bubbles in the line. It really messes up the fuel air mixture. Are there any gaskets between the pump sections?? Or are the diaphrams without gaskets.? Hard part is figuring out how the air is getting in. You may be able to blow back through the fittings with a line on them, with you mouth, and the pump under a bowl of water to see where the bubbles are getting in. If they're warped or just a rough surface, you may be able to sand them down with water paper on a glass plate to fix any blemishes. Be interesting to put a pressure gauge on the outlet, and wind it over with a starter to see how much pressure it actually puts out.

Gord.
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Old Apr 03, 2012, 07:36 PM
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Pump to carb line length test

Had a bit of time and as it is still not midday decided to put on a longer piece of fuel line from pump to carb. Engine still runs but rough as there are still bubbles coming through at first it was a lot, then it settled down as system was bled through but when I cranked the motor up more air in the line. Tested all the connections and they are fine, so it looks like it is the pump I must test next. I am wondering if there is hole there?
Noticed Mr Chan is missing with input?
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Old Apr 03, 2012, 09:01 PM
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Oopps my mistake

Pump is fine, gave it a good clean and wash, dried with air and reassembled. Noted that the fuel line out, which is now 23cm long was on a slight angle and suspected that even with it being properly secured it could be leaking air, re-led the line securing with extra cable tie.
That was it, motor running in fine, still the odd bubble but tiny and suspect it is still an air leak on the fitting.
Note extra length of line from pump to carb - no effect.
pump being lower than carb - no effect

very happy with result
Now just have to start figuring out how to fit it in to the cowl
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Old Apr 03, 2012, 10:10 PM
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Originally Posted by flypaper 2 View Post
I'm not familiar with the pump but there can't be any air bubbles in the line. It really messes up the fuel air mixture. Are there any gaskets between the pump sections?? Or are the diaphrams without gaskets.? Hard part is figuring out how the air is getting in. You may be able to blow back through the fittings with a line on them, with you mouth, and the pump under a bowl of water to see where the bubbles are getting in. If they're warped or just a rough surface, you may be able to sand them down with water paper on a glass plate to fix any blemishes. Be interesting to put a pressure gauge on the outlet, and wind it over with a starter to see how much pressure it actually puts out.

Gord.
There are gaskets. Pics of my disassembled pump 2 pages back shows a separate gasket on the flapper side and an integral one on the pressure diaphragm

I first thought my pump was blowing bubbles but not being able to see the fuel into the pump because I used neoprene line from the tank and tygon out of the pump led me astray. I discovered they were coming from the tank and installed a felt covered clunk from a mower shop and solved that issue. I forget who it was way back at the beginning of this topic said several times to use one. Learn the hard way!

I mounted the pump as pictured back some pages to a wood block mounted to the firewall level with the inlet. Mine works fine now.
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