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Old May 14, 2014, 09:02 PM
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I know mine doesn't like full throttle until it nice and hot.

Like earlwb said above set the LSN to idle with the carb set about half open, then adjust the HSN.
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Old May 14, 2014, 09:22 PM
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Thanks, I did forget to mention that the engines tend to be cold blooded and they need to warm up good before you can go full throttle.
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Old May 15, 2014, 12:25 AM
Complete RC Idiot Savant
The Netherlands
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Quote:
Originally Posted by earlwb View Post
Thanks, I did forget to mention that the engines tend to be cold blooded and they need to warm up good before you can go full throttle.
I seem to notice that tendency on every engine that I convert to spark, even though I am still running Methanol...

It is not as bad as you describe it, but noticeably more pronounce compared to the rich mixture associated with glowplug.

Some engines I have to warm up with a restrictor in the exhaust (to get a temporary richer mixture without touching the needles), and most all of them need more throttle (and RPM) to keep running immediately after start if still cold.... this I never really noticed when those same engines were still running glowplugs.

I think, it has to do with the fact that the mixture is leaner on CDI, and therefore the engine temperature (and possibly the heat transfer towards the carb) does have a relatively larger effect on the evaporation rate of the fuel: you need of course a total air:fuel ratio, but you need under all circumstances to have sufficient of that fuel evaporated to get an igniteable mixture.
Running glow needs a fatter mixture, so the ignition level is easier achieved....

That is my thinking....

I believe, this is the same reason why for example liquid cooled engines can operate more fuel-efficient: due to their better temperature control the fuel ratio can be controlled within tighter limits....

Brgds, Bert
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Old Jul 06, 2014, 08:31 PM
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Well as a further note, my NGH 9cc gas engines are still hanging in there from when I first obtained them in 2012. So I have been more or less flying them since 2012. I had my low wing plane out all this week and the engine and plane were still working Ok for me.

I think that the main needle needs to be set just a little on the rich side. When the engine gets nice and hot, it will lean out a little more. Also in the air the prop will unload some as well, so you have to get the high speed needle set to be just a little more on the rich side, but where it leans out when hot and is still rich enough to let the engine unload in the air without getting too lean.

Of course if one reads back in this thread's history they'll see it wasn't all plug and play with the engines though.

I did have some trouble this last week when I mixed up a fresh gallon of fuel to use in the engine. They had switched to the summer blend gasoline from the winter blend and it caused the high speed needle setting to change on me. So I had to fiddle around with the high speed needle some to find that sweet spot again.
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Old Jul 07, 2014, 08:39 PM
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Hervey Bay, Queensland, Australia
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I posted early in this thread about my example.

A replacement OEM carb was scourced but was the throttle rotor was far too large in diameter to assure good atomisation at wide open throttle.

The connecting rod big end phosphor bronze insert loosened in situ despite using correct oil grade and ratio fuel.

A rod off an OS .46 FX was substituted. Plug and play though it is fractionally shorter and the piston skirt required a very light filing to clear the crank web. . Running was not affected. No more rod problems.

It runs fine now though bubbles from air leaks about the pump contunue to be a problem. Remedies are set out earlier in this thread and need no further elaboration.

A good design let down by a lacklustre carberettor and poor rod.
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Old Jul 07, 2014, 09:40 PM
Eduardo
Brasil, RS, Porto Alegre
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Hello Fiery, what carb are you used to replace the original one ?

Some time ago i do some tests using the carb from my hpi savage and it worked much better than the original.

I tested with original fuel pump and using the pressure tube connected to muffler and fuel tank.

The two solution work fine to me.
The problem is that the savage carburetor is made with plastic.

regards.



Quote:
Originally Posted by fiery View Post
I posted early in this thread about my example.

A replacement OEM carb was scourced but was the throttle rotor was far too large in diameter to assure good atomisation at wide open throttle.

The connecting rod big end phosphor bronze insert span off despite using correct oil grade and ratio fuel.

A rod off an OS .46 FX was substituted. Plug and play though it is fractionally shorter and the piston skirt required a very light filing to clear the crank web. . Running was not affected. No more rod problems.

It runs fine now though bubbles from air leaks about the pump contunue to be a problem. Remedies are set out earlier in this thread and need no further elaboration.

A good design let down by a lacklustre carberettor and poor rod.
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Old Jul 08, 2014, 06:26 AM
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When at first I had grown frustrated with the OEM carb on the NGH engine, I went with using a Walbro carb adapter and using a Walbro carb on the engine. Gary Cee made this adapter for me. Walbro makes some carbs with a small venturi size that work for engines this small. But later I figured out the issues and then using the stock OEM carb was not a problem anymore.

The pump/regulator unit needs to be as close to the carb as is practical, and somewhat isolated from engine vibrations. Also the unit cannot be behind the engine as it is heat sensitive and will vapor lock from the heat. You may have to very carefully shorten the center post on the pump cover a couple of thousandths of a inch so that it puts a little more pressure onto the sealing gasket so that it doesn't leak. The stock rubber diaphragms do not do well with our USA pump gasoline and tend to get soft and stretch out in a very short time. But a Walbro K10-WAT rebuild kit has diaphragms that work good though. The teflon and blue pump diaphragms work good with the teflon one providing the most fuel pressure. The blue diaphragm less fuel pressure and the black one is in between. I also put on a larger 8/32 threaded fitting into the engine and pump regulator to increase the strength of the pulses from the engine crankcase.

The OEM carb isn't very good, but it does work. First idle speed is where the throttle barrel is about 1/2 open. Full throttle is all the way open. Once you get used to that, then the carburetor works OK. Trying to adjust the carb for normal almost close for idle to WOT does not work, it can't be done without extensive reworking the needle tapers, etc. The rubber diaphragm in the carb is just there as a gasket, it serves no purpose.

Also you really need to use a fuel filter with the engine. The jets and orifices are much more small in size and can get clogged really easily from microscopic size debris. I use a filter on the fuel container and one on the engine. A felt filter inside might be a good idea too. But I didn't try it. I also used clamps, small zip ties or wires to clamp on the Tygon fuel tubing inside and outside of the fuel tank. The Tygon tubing gets soft and can come loose from the fittings.





I was trying some ideas for moving the pump/regulator behind the engine, but it didn't work, I wound up putting the unit beside the engine up front as close to the carb as is practical too. The pump regulator is vibration sensitive and heat sensitive in that it lets gas bubbles form inside when hot (of course that could also be where the metal expands and it now lets air inside too, but I haven't tested that thought out yet).


Of course the pump regulator unit is now up front beside the engine close to the carburetor and it works well there.


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Last edited by earlwb; Jul 08, 2014 at 06:39 AM. Reason: typo correction
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Old Jul 08, 2014, 09:38 AM
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It just so happens that the Evolution 40204 rod is a drop in replacement.

Is NGH still producing engines?
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Old Jul 08, 2014, 10:57 AM
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That is pretty cool about the rod. Does the needle bearing on the rod fit too? That is definitely work a try if one has the rod problem. One possible issue is I don't know if NGH hardened the surface of the crankpin or not. That might affect the longevity using the Evo rod.

The Hobby King engines and probably the other newer engines too, are using a new rod without bronze bushings that is smaller in size and more like the rod designs seen in model diesel engines. I tend to prefer the more robust rod designs though that new rod should be fine.

NGH maybe is still making engines. They are dumping engines off via Hobby King now too.
But that tends to alienate one's importers and dealers though.
I think that HiModel in China stated that they had a parts freeze on at the time, so I don't know if NGH has let up on the freeze or not. Now the local importers or sellers may still have parts though.
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Old Jul 08, 2014, 01:10 PM
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http://www.horizonhobby.com/products/EVO100204
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Old Jul 08, 2014, 01:15 PM
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oops sorry my fault, I was thinking of their gas engine. I forgot about the glow engine. So that is really cool. That is a nice find there gkamysz. Thanks for sharing.
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Last edited by earlwb; Jul 08, 2014 at 01:15 PM. Reason: typo correction
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