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Why can't walbro type carbs work on glow? - 12/6/2012 5:46 AM   
Ernie Misner



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Status: offline 		Why can't a "walbro type" carb work with glow fuel? Assuming it was built for methanol of course. Seems like it could work off of crankcase pressure pulses to the diaphram, the tank could be placed on the CG if desired (far from the engine) and NOT require a pressurized tank.

Thanks, Ernie Misner

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 5:55 AM   
TFF


 

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Status: online 		It can if you can re-jet for glow fuel.

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 9:12 AM   
Reverend



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Status: online 		MVVS has been doing that for quite some time. afaik theres a 26cc and a 35cc with walbro carb.

rev

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 10:39 AM   
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Status: online 		They work fine with glow fuel.

Try it.

Just run your petrol engine from a tank of glow fuel. You'll need to adjust the jets, of course. I tried it years ago, with a Quadra 42. As I recall, there were no particular problems to overcome ... but this must be nearly 20 years ago, so I may have forgotten. There's no advantage to it, of course.




Re-reading the OP, I'm now not sure whether you are really asking whether we can run glow engines, using Walbro carbs ... rather than whether Walbro carbs will work with glow fuel.

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 11:27 AM   
Ernie Misner



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Status: offline 		Thanks for the replies guys. The question is why we don't see small glow engines that use a demand type fuel supply that does not require tank pressure and the tank can be further from the engine like walbro type carb setups.

Thanks, Ernie

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 12:13 PM   
bogbeagle


 

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Status: online 		OK... I would guess that it's a question of economy. Maybe there's an element of KISS, too.

I expect that it's easy to convert your own, if the engine is large enough to tolerate a big lump of Walbro. I must get around to trying that.

Lots of people use the Walbro ... in conjunction with the regular glow carb .... to provide a regulated fuel supply. I sometimes do this. The idea is to use just the Walbro' pump and its regulator to provide a consistent fuel supply to a conventional glow-engine' carb. It works. Obviously, this adds weight and bulk to your installation.

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 12:22 PM   
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Status: offline 		A Walbro type of carb setup for alcohol works fine with glow fuel.  OPS did it with their Del Orto pumper carbs too.  MVVS of course used one on some of the bigger glow engines. Walbro sells one the WT-499 carburetor which is a alcohol carb. 

Normally you need to open up the jets as they need to flow more fuel. But other than that it is the diaphragms that need to be alcohol rated. The diaphragms may last for a while though, it depends. But the current more modern carbs are designed to handle 10% to 85% alcohol in the fuel already, so you may not have to do anything about them.

I have a SV 17cc engine that I got used from someone else. When I ran the engine, I couldn't adjust the carb to lean out the engine at WOT. It was always running too rich. So I replaced it with a different one.  But now I think maybe it was setup more for E85 or M85 fuel with 85% alcohol. So it might work fine with glow fuel then. But I haven't tried it.

But you cannot beat the simplicity of a glow engine that uses a relatvely simple carb and muffler pressure. It is amazingly reliable and works well.


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RE: Why can't walbro type carbs work on glow? - 12/6/2012 12:31 PM   
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Status: offline 		OS have a line of pumped glo fourstrokes if you like them.

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 5:02 PM   
pe reivers



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Status: offline 		Some 10 years ago I used a ST2300 glow engine with standard carb and a Walbro carb as glow fuel pump with exhaust pressure on the regulator. That worked like a charm for at least two years using the same inner Walbro parts.


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RE: Why can't walbro type carbs work on glow? - 12/6/2012 5:38 PM   
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Status: offline 		I have run an ST 2300 using the Walbro WT499 carb and 10% Omega fuel - it runs very well using this carb and the OS F plug or the Fox long plug.

You do need to get an adaptor to mount the WT499 on the 2300 and you also need to tap the backplate to get the pressure pulse for the Walbro.

Ed

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 6:30 PM   
Ernie Misner



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Status: offline 		Old Fart, does the OS pumped line of engines still use tank pressure?

Pe, am I correct in assuming your ST2300 / Walbro pump did not use tank presssue? That is what interests me is the Walbro type setups that do not use tank pressure and the tank can still be mounted far from the engine.

Thanks, Ernie

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 7:25 PM   
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Status: offline 		You have equivalent choices like a Perry pump and pump carb combo running off crankcase pressure, or, a Perry pump running off crankcase pressure and the stock carb with a demand regulator near the carb to allow it to meter the mid-range properly.

I would think you don't see a Walbro type carb on the majority of glow engines is that it would drive the price point up significantly (look at the price delta between regular glow engines and the pumped versions for pattern), many engine/plane configurations don't need it, and the physical bulk of the system relative to engine size if it were an integrated pump/regulator/carburetor. Walbro carbs are cheap due to mass production for the consumer product market. For the glow engine marker a wide variety of bore sizes would be needed for the range of engines produced, and they would have to be developed and manufactured by the engine manufacturers themselves.

I could be wrong, but I tend to think cost wise the RC consumer does better with after market systems like the Perry for specific applications that require it. But yeah, it sure would be nice if an integrated pump/carb system was standard equipment on all our engines!

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 10:17 PM   
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Status: offline 		The YS DZ line of engines have mechanical fuel pumps with direct injection. No tank pressure needed.

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 10:25 PM   
Ernie Misner



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Status: offline 		Okay, that's what I was wondering about. My YS 70 had the diaphragm but still used tank pressure. Thanks Mike. Looks like it's very doable and a few do use the 'no tank pressure' method. Like was stated before, probably the extra expense and parts keeps it from being mainstream.

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RE: Why can't walbro type carbs work on glow? - 12/6/2012 10:36 PM   
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Status: offline 		Hi ernie the os pumped glo fourstrokes don't need tank pressure.Some guys run a straight home made pipe with no muffler and they sound nice.

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RE: Why can't walbro type carbs work on glow? - 12/7/2012 6:06 AM   
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Status: offline 		Real reason is that for a manufacturer to buy a walboro carb for their glow engine probably costs them as much or more as making the whole engine.

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RE: Why can't walbro type carbs work on glow? - 12/7/2012 6:09 AM   
Ernie Misner



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Status: offline 		Correct, but engines could be designed with a diaphram using pulses from the crankcase and we all could put our tanks on the CG. No walbro needed.

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RE: Why can't walbro type carbs work on glow? - 12/7/2012 10:36 AM   
bogbeagle


 

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quote:

ORIGINAL: Ernie Misner

Correct, but engines could be designed with a diaphram using pulses from the crankcase and we all could put our tanks on the CG. No walbro needed.




Well, they are designed like that.

Plenty of pumped engines on the market.

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RE: Why can't walbro type carbs work on glow? - 12/7/2012 12:08 PM   
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quote:

ORIGINAL: Ernie Misner

Correct, but engines could be designed with a diaphram using pulses from the crankcase and we all could put our tanks on the CG. No walbro needed.


They used to do that. K&B, OS, ENYA, WEBRA, HP and HB all had pumped engines. They normally used a Perry pump built into the backplate of the engine. It salso came with a larger bore carb in most cases too, as the engine didn't have to draw fuel with the pump.  Now then Enya got fancy with a few engines using a "geared pump" and OS also came up with some of their own design pump systems too.

Unfortunately, the pumped engines weren't all that popular so they all pretty much stopped making the engines like that. I think they all decided that if someone wanted a pump then they could get it themselves. Maybe a it was a cost or price point decision. There are still a few specialized engines that have pumps on them being sold though.

A classic example is a old K&B .40 engine with big bore carb and the pump built into the backplate. At the time K&B had pumped versions of most of their engines.









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RE: Why can't walbro type carbs work on glow? - 12/8/2012 3:06 PM   
pe reivers



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quote:

ORIGINAL: Ernie Misner

Old Fart, does the OS pumped line of engines still use tank pressure?

Pe, am I correct in assuming your ST2300 / Walbro pump did not use tank presssue? That is what interests me is the Walbro type setups that do not use tank pressure and the tank can still be mounted far from the engine.

Thanks, Ernie

No tank pressure, and still using the original glow carb. Muffler pressure goes to the regulator on the walbro.
see http://prme.nl/home/regulated_fuelsupply/a_regulated_fuel_supply.html for the complete rationale, building history and pictures.



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RE: Why can't walbro type carbs work on glow? - 12/8/2012 6:04 PM   
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Status: offline 		The OPS maxi 30cc used a walbro type carb. It works equally well for gas or glow as issued. By simply adding an ignition system these engines run perfectly with gasoline. The carb only needs to be adjusted.

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RE: Why can't walbro type carbs work on glow? - 12/8/2012 7:49 PM   
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Status: offline 		Here is my st2300 with the wt499 carb mounted in place of the original carb. Runs very nicely on glow fuel as I mentioned above.

Ed

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RE: Why can't walbro type carbs work on glow? - 12/8/2012 10:00 PM   
pe reivers



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Status: offline 		Throttle management with the walbro carb is not nearly as good as the original rotating barrel glow carb (after some mods). For the same linear response you would need a type WYK Walbro, which also is a rotating barrel carb type with integrated pump and regulator.


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RE: Why can't walbro type carbs work on glow? - 12/8/2012 11:14 PM   
rc34074


 

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quote:

ORIGINAL: pe reivers

Throttle management with the walbro carb is not nearly as good as the original rotating barrel glow carb (after some mods). For the same linear response you would need a type WYK Walbro, which also is a rotating barrel carb type with integrated pump and regulator.



I did not find any noticeable difference using the wt499 compared to the chinese carb that came on the 2300. They both ran very well. Iflew my 81 inch mustang with the setup you see above - no issues. So I guess we will have to disagree. To me the wt499 is an excellent alternative carb to the chinese 2300 carb.

Ed

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RE: Why can't walbro type carbs work on glow? - 12/9/2012 6:19 AM   
Ernie Misner



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Status: offline 		If the butterfly works the same as with gasoline most folks say the throttle response is not linear. Various workarounds like the throttle linkage setup shown in the Sticky for gas beginners in the gas forum try to smooth out the power curve. Without that or a throttle curve or expo most of the power comes on with very little opening of the butterfly and then the last portion before full throttle not doing so much. I can see why there would be advantages to the barrel type throttle setup.

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