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Old Jan 08, 2013, 12:58 PM
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Fuel Vapor Carburetor

Anyone tried running their gas engines off a vapor carb design?

This is a very controversial subject in the automotive world regarding fuel economy. Some say it works great, others say it has no impact on fuel economy at all and is a sham. Maybe scaling down we might see better results.

The idea is to introduce fuel to the motor in a vapor form, as opposed to a liquid or atomized form. The vaporized fuel is sent through a heated tube to the motor so it does not condense before ignition. From watching basic youtube videos, it seems the motor produces less power at any given RPM, but has an increase in economy.

Some setups drip tiny drops of fuel on a very hot surface to produce vapor. Other designs use ultrasonic foggers often found in terrariums or cheaply made desktop fountains.

What's your take on all of this? Do you think a vapor carb design for a RC gas engine would benefit its fuel economy?
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Old Jan 08, 2013, 01:13 PM
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Raw fuel will not burn, therefore, an engine will not run unless the fuel is in vapor form. The fuel turns to vapor inside the engine. The intake runner is warm to hot and the cylinder is hot to very hot. This does the vaporizing for you.

IMO, with the advent of fuel injection, a vapor carb is just more snake oil.

For our purposes, a vapor carb is not practical nor needed.

Ken
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Old Jan 08, 2013, 01:22 PM
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It wouldn't help in a model engine, except maybe to test or prototype a concept for a patent or something. But for larger vehicles they have the natural gas powered engines that use something like a vapor carb, except they don't have to cause the fuel to vaporize. If I remember correctly, quite a few early internal combustion engines used vapor methods for running back in the late 1800's to early 1900's too. It wasn't all that great as the throttle was pretty poor with the engines then. Some engines didn't even use a throttle either. I would think that if the engine designers had all abandoned the vapor carbs many years ago, then there are reasons why they did so.

For a model engine a vapor carb would add more complexity to the mix plus add weight as you need to have a way to vaporize the fuel too. Using natural gas might be more practical, but then you need a small pressure tank and a way to charge and discharge the tank too.

Model glow engines actually depend on the methanol to help cool the engine. As the methanol vaporizes inside of the engine, it draws heat away from the engine. There are some racing glow engines that actually have little to no cooling fins on them as the methanol is what is helping to cool the engine maybe more than the air is doing.

But sometimes someone doing something that everyone thinks won't work out is what keeps the world going. If you are going to do it, go for it. There is always something to learn about whether it works or not. It could be interesting and fun for you too.
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Old Jan 08, 2013, 01:40 PM
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We sometimes make our carbs out of plastic or have a barrier between the carb and motor to keep the carb cooler. At the drag strip guys have ice packs on the intake plenum to keep the air charge cooler. This is all for more power though. Something could be made up easier on a model 2 stroke motor much easier than a car motor just to do some tests if you want to try. I would think a tube from the muffler going through the carb or fuel line somehow might get the effect and you could take rpm readings before and after to compare, maybe time a tank at full throttle to compare mileage. Tell us the results in case they are good!!
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Old Jan 08, 2013, 02:04 PM
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RxFPV,


How do you suppose the oil (in all our model fuels; gas, glow, four-stroke and two-stroke) will evaporate? Will it still lubricate?

I am skeptic regarding the feasibility of such an endeavor.
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Old Jan 08, 2013, 03:59 PM
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Quote:
Originally Posted by earlwb View Post

Model glow engines actually depend on the methanol to help cool the engine. As the methanol vaporizes inside of the engine, it draws heat away from the engine. There are some racing glow engines that actually have little to no cooling fins on them as the methanol is what is helping to cool the engine maybe more than the air is doing.
FWIW
The Top Fuel drag engines are a solid chunk of aluminum. I think mostly for strength but there is no cooling other that the fuel going through the engine and the air going past. And maybe a bit from the oil???

In any case they survive, even though they do not run for very long period of time. I think.... I read someplace they sometimes have a bit of trouble getting the engines up to temp before a run.

Ken
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Old Jan 08, 2013, 04:01 PM
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Thanks for all the replies. Seems it wouldn't bee too much of a benefit to the hobby world. Fuel injection is known to be the most precise form of fuel delivery. Some small commercial UAVs already use fuel injection to achieve 8+ hour loiter times consistently. Some vapor carb designs I've seen almost work like throttle body injection. Not as efficient as direct port injection, but still more precise than a carb (in theory). Honestly, I haven't spent much time reading up on the topic, thought it would make good conversation.


Quote:
Originally Posted by aspeed View Post
At the drag strip guys have ice packs on the intake plenum to keep the air charge cooler. This is all for more power though. Something could be made up easier on a model 2 stroke motor much easier than a car motor just to do some tests if you want to try.
Maybe something like a peltier cooler. They're used in CPU cooling. Add current to the plate and one side gets hot, the other cold. The "cooler" the hot side, the colder the cold side gets. Could maybe make a miniature heat exchanger to cool the air before it gets to the carb. The problem is they require a lot of power to run.

Quote:
Originally Posted by DarZeelon View Post
How do you suppose the oil (in all our model fuels; gas, glow, four-stroke and two-stroke) will evaporate? Will it still lubricate?

I am skeptic regarding the feasibility of such an endeavor.
I'm not too sure, this would definitely be a problem. Oil injected 2-stroke outboards sip oil, but this would add complication/weight to these small engines.


Found this:
Petrol Vapor Carburetor Final Design.wmv (4 min 34 sec)


His other videos are great too
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Old Jan 08, 2013, 05:38 PM
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OS engines are the only ones that made a couple RC engines that actually used fuel injection. They even had a ECU computer module for them too. Unfortunately they didn't make too many engines and they disconitnued production too. Only the high end competition aerobatic flyers who were sponsored by their countries' importers got the engines.
I think the smaller engine did get sold to a number of flyers though. But OS still had a short production run in any case.
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Old Jan 09, 2013, 12:05 AM
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Quote:
Originally Posted by earlwb View Post
OS engines are the only ones that made a couple RC engines that actually used fuel injection. They even had a ECU computer module for them too. Unfortunately they didn't make too many engines and they disconitnued production too. Only the high end competition aerobatic flyers who were sponsored by their countries' importers got the engines.
I think the smaller engine did get sold to a number of flyers though. But OS still had a short production run in any case.
A few of those did enter our tiny country and this is one of them, the OS FX 140 FI Electronic Injection.
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Old Jan 09, 2013, 08:21 AM
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RxFPV, That vapor carb device on the Otto engine was quite interesting. It is amazingly simple looking too. But I suspect there are some subtle design features to it though.

That is a nice engine Reginald.
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Old Jan 09, 2013, 11:22 AM
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Originally Posted by earlwb View Post
RxFPV, That vapor carb device on the Otto engine was quite interesting. It is amazingly simple looking too. But I suspect there are some subtle design features to it though.

That is a nice engine Reginald.
I guess it is one of only two that were imported here in Belgium. I have no use for it but I bought it when one of the larger modelshops here sold out. I would like to know what the sale price in the USA was ?
I have seen Otto model engines before but never this system.
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Old Jan 09, 2013, 12:07 PM
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Wouldn't a regular carb be fuel injected? With a bladder?
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Old Jan 09, 2013, 01:43 PM
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Yes using a bladder, sort of, more or less, results in a "Single Point Fuel Injection system". I remember that from some advertising hype on car engines years ago. But the bladder results in a system that doesn't have a ECU controlling it for more precision. Then there were the mechanical fuel injection systems that were quite popular for years in drag racing, etc.

I got to thinking about it, but the vapor carb design depicted above would only work for a stationary engine. It wouldn't work well at all in a moving environment, much less aerobatics.

Reginald, I don't think OS sold that 1.40 FI engine per se. I suspect that they only sold them to the importers (maybe gave?) who provided the engines to certain competition pattern flyers to use. I think OS wanted to see what would happen when more people used them. But they wanted to limit the exposure to a select few.
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Old Jan 09, 2013, 02:30 PM
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It would be nice to hear from someone who actually used the engine to get their take on it.

We are starting to see FI on some of the Stihl products now. More will be coming as the feds turn the screws tighter on emissions.

Ken
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Old Jan 09, 2013, 03:58 PM
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I had read that the one or two flyers in Australia who used some OS fuel injected engines, they had trouble with the engines and may have damaged a couple getting them, figured out. I think their importer sponsor gave them like five or six engines to use.

I looked around and OS had the 1.40 like Reginald displayed, OS also made a 200 four stroke and a 91 four stroke fuel injected engine too. The 91 was sold via Tower Hobbies for a few years. It shows up on Ebay from time to time. But heaven forbid if you need parts for it anymore.

I think they were quite expensive and thus had low sales because of that, so OS probably gave up on it at the time.

But it might be tricky to get used to without any needles to adjust. You have to tell the ECU or program the ECU for the air/fuel ratio, no needle adjustments.

the FS-200 FI
http://www.os-engines.co.jp/english/...0sfi/index.htm

The 1.60 FI
and http://www.rcgroups.com/forums/showthread.php?t=1131061

and the .91 FI
http://www.rcgroups.com/forums/showthread.php?t=1092313


One guy using a 1.60 engine really liked it, that was way back in 2005.
Quote:
I use the OS 160 FX Fuel Injected engine in one of my aircraft. With no neadles to play with, it never misses a beat and has a great throttle perfomance. I do know it is still manufactured and available from both Japan and other countries.
About 2 or 3 years ago, there were rumours that OS were about to produce a Fuel Injected version of the OS 91 heli engine. I guess this was dropped in favour of the Pumped version.

Modtron
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