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Old Dec 29, 2012, 04:20 AM
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AA5BY's Avatar
East Texas
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Originally Posted by DarZeelon View Post
Yes, Ernie.

All gas engines use a diaphragm-pumped carburettor.
It can be a Walbro, a Tillotson, or one of their own (the engine manufacturer) design.

The pump is either integral with the carburettor (preferred), or separate.
I'm not thinking this carb has a pump but I could be wrong. It refers to a regulator but because it has a muffler pressure tap, that might be the pump and because the volume of fuel is so slight, it is probably fine.

We will soon hear about any fuel issues if they exist. My installation will be inverted and will place the barrel somewhat below the center line of the tank. We'll see how that goes.
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Old Dec 29, 2012, 04:26 AM
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Although the carbs look similar, the NHG requires an external pump properly located for it to work correctly. Appears the EVO10 has improved the carb regulator to use only tank pressure to operate correctly.
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Old Dec 29, 2012, 05:35 AM
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Originally Posted by flyinwalenda View Post
Although the carburettors look similar, the NHG requires an external pump properly located for it to work correctly. Appears the EVO10 has improved the carb regulator to use only tank pressure to operate correctly.
What?
A gas engine carburettor that does not have an integral (or or has an add-on) diaphragm pump?

This looks like a problem source to me.
Glow fuel will work properly at a rather wide fuel-air range.

Not so with gas...
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Old Dec 29, 2012, 06:14 AM
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NGH comes from a long way to find a solution of fuel feed for GT9 due to no chance to use a Walbro carb.Michael said muffler pressure didnt work so they have to add a separate regulator/Pump.But Evo seems solve the problem by muffler pressure.
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Old Dec 29, 2012, 09:16 AM
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Quote:
Originally Posted by DarZeelon View Post
What?
A gas engine carburettor that does not have an integral (or or has an add-on) diaphragm pump?

This looks like a problem source to me.
Glow fuel will work properly at a rather wide fuel-air range.

Not so with gas...
Way back in the 1920's, 1930's and early/late 1940's, the model gas engines had no regulators or pumps but they still worked OK. Some of those engines even had crude throttles on them that worked too.

Yes the Evolution carb has a regulator but no pump, it uses muffler pressure.
The NGH carb uses a external pump/regulator unit.
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Old Dec 29, 2012, 10:29 AM
nickeast
Stuart,FL
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Ok... I'm interested.... can someone give me the expected thrust that this little beast will deliver? In pounds.... I've seen the hp comments but I just like to keep it simple .... necessary for me.

Nick
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Old Dec 29, 2012, 10:32 AM
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Originally Posted by turk1 View Post
...But Evo seems solve the problem by muffler pressure.

Turk,


That is the point... I don't think any problem was actually solved...

Glow engine carburettors (except those designed to use a pump) rely on fuel suction through Venturi depression for fuel delivery.

Muffler pressure used to pressurize the fuel tank, is to the order of .25-.50 psi, which is minuscule (pumped fuel delivery is about 5 psi).
Exhaust pressure is too low even to overcome leaning when pointing the nose up, even if the tank is smack against the firewall.

One of the virtues of gas engines as a class are their pumped carburettors.

I believe this externally attractive engine, which also appears to be of good quality, will prove to be 'half-baked', due to this oversight.

I believe Horizon Hobby should have delayed exposing this engine, until devising a pumped carburettor that will fit. Or they could have used the larger frame engines of the same manufacturer (Sanye .61-.91 engines), onto which the smallest Walbro/Tillotson carburettor (with diaphragm pump) will fit.
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Old Dec 29, 2012, 11:04 AM
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Dar Zeelon, actually the Evolution engine design, especially the carburetor system was pretty well developed way back in May 2010 when the Magnum .52 was first shown to the public. But even though they were test flying the engines in airplanes, it was only until December 2012 before they started selling them. So they do not appear to have been in a hurry to put them out on the market. I think they carefully tested the engines for a long time too.

Old pic of the Magnum .52 prototype, I assume it had been under development for a year or so before it went public a couple of years ago.
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Old Dec 29, 2012, 11:05 AM
Two left thumbs
Muncie, IN
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Why not saw a Walbro in half, epoxy or tap & screw a fuel fitting into the outlet, add an impulse line, and place it right behind the engine? Free carbs can be had at any small engine repair shop - they usually have boxes of them! I probably have fifty Zamas and a dozen Walbros, since I work for a Stihl dealer and they use Zamas. Either will work.

Geoff
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Old Dec 29, 2012, 11:24 AM
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If someone really wants to, they can make an adapter for mounting a Walbro carb onto a small engine too. I have done it already and it works fine like that too. But it isn't exactly all that aesthetic though.



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Old Dec 29, 2012, 12:07 PM
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Quote:
Originally Posted by earlwb View Post
Dar Zeelon, actually the Evolution engine design, especially the carburetor system was pretty well developed way back in May 2010 when the Magnum .52 was first shown to the public. ...
But still, Earl, there is no diaphragm pump integrated into this carburettor...
So, fuel feed is like it is in a glow engine.

And a simple silicone pressure tube obviously cannot be used. Even Tygon and Neoprene deteriorate rapidly, so they specify Viton.
Why not just a pump? All gas carburettors have it.
The pump is a feature a gas engine cannot go without!

All Saito four-stroke gas engines, from the FG-14, have a pumped carburettor.
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Old Dec 29, 2012, 12:48 PM
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Originally Posted by earlwb View Post
Way back in the 1920's, 1930's and early/late 1940's, the model gas engines had no regulators or pumps but they still worked OK.
http://www.reginaldluycx.be/collectie.html
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Old Dec 29, 2012, 01:02 PM
EIEIEIO Classic is dway ta go!
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I haven't started mine yet(getting dumped on with snow today...joy) but I would say any air leaks in this system will quickly affect the carb. Also as mentioned I'm wondering how this system will perform inverted. We will see !
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Old Dec 29, 2012, 01:27 PM
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Originally Posted by earlwb View Post
Way back in the 1920's, 1930s and early/late 1940s, the model gas engines had no regulators or pumps but they still worked OK. Some of those engines even had crude throttles on them that worked too.
Earl,


You're not that old... And even if you are, how many aerobatic R/C planes do you suppose there were then?

The first single-channel reed systems did sprout in the '40s, but pattern flying began in the late '60s... And everyone was flying glow then.
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Old Dec 29, 2012, 02:29 PM
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Quote:
Originally Posted by DarZeelon View Post
What?
A gas engine carburettor that does not have an integral (or or has an add-on) diaphragm pump?

This looks like a problem source to me.
Glow fuel will work properly at a rather wide fuel-air range.

Not so with gas...
With the built in Regulator, this carb works perfectly with muffler pressue. At least mine does. Do you own one?
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