Billy603

Good afternoon.

I have now converted a Saito 82 4st glow and a Os 62 4st glow to Gas.
First, please note that it is absolutely, completely and enthusiastically worth it !

Now, my set was made with Brutus (Bert) parts and help.
God did I learn a lot about engines !

I went through all the mistakes and mishapps possible, but now it is a delight.

I would like to share here with you folks my learning curve. If you do it exactly as I say, you will have an immediate success and you will know WHY.

Converting to gas from glow is changing a carburation setting from extremely voracious to extremely sparse: 125 cc glo will last some 15 min, 125 of gas will last more than one whole hour !
Cost of gas is peanuts, cost of glo fuel is platinum. No more killing your bearings with gas.
This sparsity comes as a now very thin flow of gas you will use, which has to be mixed very precisely with the exact amount of air. That is done by inserting in the gas line a tiny solenoid valve which will regulate it very very precisely. It is powered via a tiny processor fed by special 'valve' curve from the Tx, see that down under.
Glo will take it +/- 6 clicks, gas will take it +/- 1 click.

That means you have to use a very good gas feeding line! I will give you the exact list of components, please stick to it !! it will save you hours !

You will need:
* a special tank made for gas, 125 cc is perfect.
* a tiny tank which will catch any crap coming from the pressurisation line. 50cc is plenty, I use a pill box, 20cc big. Check for proper airtightness.
* Those yellow special piping for gas. I found mine on Amazon for a few euros the 3ms. Take both 2.5mm and 3 mm sizes.
* Bert's solenoid set, which is a gas regulator with a tiny computer device (totally ready to use, no need to program it yourself) in it. Take his, I made mine but it died after a few hours. His is flawless and tiny. Cost is peanuts too.
* the usual ignition set, please also take the timing device which will allow precise installation, and the rpm meter.
* a special FELT tank clunk. I have tried the others, they let you down. The felt one is the best and only. You can find it in your usual garden equipment store.

You will be fiercely hunting for any bubbles in your feeding line: Using this yellow piping makes it easier since it sticks to whatever it is connected to.
Do not waste your time with any type of other piping stuff !
-Piping diameter: Bert supplies his set with 3 mm outlets. Use the 2.5 mm one you bought, I had air leaks (bubbles) with 3 mm.
-Use some standard silicon piping for the pressure tap, The yellow would melt.
-Do not even dream of using this silicon piping for the gas line: it will not only dissolve (!) but also let a ghastly goo to pollute your carb !
-Isolate your carb from the engine heat with a piece of plywood or carboard shield.
-Loctite your screws to the engine, if not they may get undone because of the vibration pattern, which is harsher. The engine does not vibrate more than with glo but those vibes are harsher.
-I cleaned my carb with hot water and soap in a ultrasonic bath because I had to get rid of the goo there was everywhere.
-Have short gas lines without big bends. Remember we are dealing with minute flows now !

Now, the start.

Please understand you will have to let your engine run for at least 6 hours (this is about 1 liter of 8% mix oil in gas), in order to get rid of any remains of glow combustion and proper breaking in. It will start to run well after those 6 hrs. Not before.
You will need an electric starter in the beginning.
The idea is to start the engine and adjust the throttle as well as you can. Remember, one click is a lot.
On your radio set, you will have to program a throttle curve and delay (delay is from full to 0 in 5 seconds), because it must be gentle. I will let you further down see which one I use with success.
Bert's supplied set is a tiny thing you connect to a special channel on your TX, to which you feed a 'valve' curve. This is to reduce in 9 steps the gas flow to exactly what is needed for every step of engine speed.
So, 2 curves in all: a 'Thr' curve on Channel 1, a 'valve' curve on Channel x connected to the valve set.
The pressure tap is crucial, it is the one which will push the gas and air to the carb. The flow is so minute that without it it won't work.
When those are connected you can check it works by hearing a soft clicking which is the noise of the valve working according to the valve curve.

What adjustments will you use: with glo, you start with some 2.5 turns of main needle, here start with 0.5 turn.
Do prime your carb well enough to eliminate bubbles and apply the starter while gently moving the Thr stick.
At one point it will start ok because your Thr position corresponds to a needle adjustment which corresponds to the proper valve curve point.. Let it heat up there for at least one minute. It will be quite poor but will run. Target a start at 50% Thr stick.
Then try to rise the thr. Your engine will disagree, then you add +/- 1 click. You will see if the engine dies or accelerates. It starts very easily (better cold), so redo it if needed. Let it run like that for some 15 mn then go on rising your Thr stick, everytime +/- 1 click.
When you are more or less at full Thr, let it run like that for some ... hours, to break it in. Total consumption: about 1 liter. Gas is mixed with 8% synth oil.
When it is done, you will notice that:
* the engine compression is now excellent
* the adjustments are frank and easier every time.

It is now time to start gently and slowly lowering the Thr and adjust each valve curve point on your TX for the best engine speed and response: for ex if your Thr is down to 50%, adjust the 50% valve curve point. These adjustments are done +/- 5 % maximum, let the engine adapt. Don't forget your are letting a tiny flow of gas in !

Idle adjustment is easy but ONLY at the end of the whole process: do not try to get it at the beginning, it will change and not stay steady being much too fast in the beginning, before everything sits in properly. My Saito idles at 1850 rpm +/-.

What happens to the Lo needle of your carb ? nothing, it is replaced by that wonderful little solenoid valve. Forget about the Lo needle.
You will never have to re adjust your valve curve once it is done. You may just wont to fine tune it at some point.
Please note that accelerations are medium easy because it breaks a pressure balance in the carb and needs a few moments to adapt (thus the Thr delay). They get better with time and breaking in. When they are fine, your engine is optimal.

My 9 points curves:
THR:-100; -85; -67; -50; -30; -5; +24; +56; +100
Valve: -62; -63; -61; -55; -42; -22; +2; +28; +59 THOSE VALUES YOU WILL HAVE TO ADJUST for your own engine ! they are only a starting point.

I now would like to thank Bert (aka Brutus) without him I would never have succeeded. He is probably one of the best engine engineers you can find and he spent so much time explaining me all sorts of things until my final success that I consider him as the King ! Thanks also to Raleighcopter, who is the valve's controller set designer: tiny, reliable, absolutely excellent. Makes life so easier and you won't have to question it.

Have a good time !
Billy

1967brutus

Wow, Great summary, Guillaume!

We could really use this for those that are new to the matter. Can we (I am asking your permission here) use this thread to guide the beginners in conversions? So they can ask questions and receive help?

Again, great summary. Happy flying!

Billy603

dear Bert
Of course ! that is what it is for.
Thank you again !

Billy

Jesse Open

That was Great!
Everything a person should know before converting an engine to gasoline fuel. Well done.

Raleighcopter

welcome to the fray, billy603. come join us in our gas conversion thread. its a BS free zone over there.

Billy603

Thanks Raleighcopter, I should have mentionned your input and work in my acknowledgments ! you are the creator of the tiny valve controller and I am very happy with it ! thanks again. It is great all along.
Let us make lots of converters to convert lots f glo's to gas !
Have a good time and keep on the excellent work !

Raleighcopter

no need to mention me, although i'm glad to see you are happy with the system and that it is working for you.

Billy603

One question appears, in the adjustment process: on the ground evrything is fine and adjusts ok.
Now when the plane moves forward to take off the engine refuses to accelerate and stops unless I turn back the Thr to 40 - 50%. it then idles extremely low and long.
What do you think ?

1967brutus

My money is on the full throttle mixture being a touch too lean for flight.
Take an RPM reading of peak RPM on the ground, and tune for approximately 500 RPM rich off peak.
Harsh acceleration also plays a role. I have a longtime habit of first getting the plane to roll before advancing the throttle further. This is for safety reasons (most of my planes are taildraggers, so getting a bit steering speed first is anyway is the safe thing to do) but it also builds u some RPM and muffler pressure before acceleration happens.
Mind you: in the air, forward accelerations NEVER are as harsh as the initial acceleration from standstill on the ground. So don't think of it as a problem.

But as said, my money is on a too lean setting.

Billy603

Now, some details about the breaking in process.

However old your glo engine is, it certainly is internally coated with glo and oil residues. Those make it airtight and give you a proper compression.

Now you are on gas, you must get rid of this coating and replace it with the gas + oil one.

This takes some time and you have to be patient about it. It does take time but you will soon see your engine become more consistent, easier to adjust and to start.

How to know that you are broken in ? well, I think a good sign is that the accelerations are getting easier and easier. It will be almost pefect when you are done.

So, here is the way:
* Disconnect your ignition Vcc supply !
* Prime heavily your carb. When the the carb feeding pipe is full of gas, go on turning the prop clockwise for two or three turns.
* Then open your carb around mid Thr .
* Power on the ignition
* use your starter. If it does not start then move your Thr a bit more open or closed.
At some time it will start coughing and will start.
* let it heat up where it is, restart if it stalls, opening the needle some 1 click.
* When hot, move up your Thr until full open.
* Then adjust your main needle, remember one click is a lot ! Check for the best RPM and make it one click richer then.
Let it run like this for 3 hours, of course you can stop it as you want, and restart.
after some 3 hours, you will see the engine is getting much better. Start adjusting your Valve curve, 1 or 2 % at a time, checking for the behaviour. At the beginning, 1 or 2 % will be sometimes enough to stall the engine. No problem with that.
* then start lowering your Thr. Your curve has 10 points from 0 to 100%. Each curve point corresponds to each of your Thr stick positions( -50% is one quarter of total, 0% is middle, etc).
* adjust for your best RPM and accelerations. At the beginning those will be poor, this is normal.
* Run the engine for another 2 hours, adjusting each point.
Normally the curve points I gave you are a very good starting point.

After some 5 or 6 hours (not less), your engine will start easily, accelerate well and have a steady RPM. It is then broken in.

Do not get despaired if it is long, let things adapt. Be patient it will work for you too !

Now is time to adjust the first curve point, the idle one, which will allow you to start by hand with one or two flips. As usual, adjust the curve, until you reach the first point. Take your time. Adjustments are 1% at a time: your engine will then show a unique curve, adapted to his own self.
This can only be done when the engine is broken in, for success.
Then it will idle long and steady and low.

After all this, go back to your curves on your TX and tick the "smoothe" option, to let the curve become round and continuous with no edges between points. Do this for both THR and Valve curves.

One point: a converted glo does heat more than a glo. Remember this when setting the engine under a canopy ! just don't, or organize a sufficient air flux for proper cooling !

Before flying your engine for the first time, adjust for one click richer because it will have less load on the prop when in the air since the plane goes forward. If you don't, the engine may overheat or stall.

Landmarks:
1) an engine which stalls brutally at any Thr position is too lean: add 1 click to better feed it. Or 2 if needed.
2) any difficult start is because of insufficient priming on the carb. Start with a low Thr opening.
3) fly your engine 200 RPM richer than peak RPM, so it does not heat.
4) any bubble in the piping will lean your engine and adjusting is then impossible. There are some bubbles to eliminate during the first minutes of running. You can check on this by watching the carb input pipe . It is useless to try any adjustments before you got rid of those bubbles.
5) an engine starts rather better when cold.
6) Don't forget to insulate your carb from the cyl heat, with some piece of plywood or heavy cardboard.
7) I use gas with 8% lawn mower synth oil. If you are worried you can use 10% in the beginning. Keep the engine oil vent open.
8) One single Hi needle click corresponds to roughly 15% on the valve curve. Adjusting the needle will correspond to moving up or down (richer or leaner) all of your curve points.

Enjoy !

Eastflight

Just what I am looking for..... A project for the winter season.
Thank you

1967brutus

It will most definitely keep you occupied for a while, and it really is worthwhile.

Billy603

Now, let me explain the very first Hi needle adjustment for your first start.

I advise at the beginning to set the Hi Needle at one half of a turn (from closed).
At this point, the gas quantity flowing will correspond to a proper quantity of air which will be found by moving the Thr stick. The engine will start when needle and opening will correspond.
Usually, we adjust the needle for a given carb opening, which corresponds to a given air flow.
Here we do the opposite: we adjust gas needle first and then find the proper air input by adjusting the Thr carb opening.

This will allow your engine to run and start breaking in.

After some time (say 15 min), you will rise the Thr a bit and open 1 click the gas needle. Then you will refind the proper air input by adjusting the Thr to match the new needle position and let it run (another 15 mn), this time the engine will run faster , more RPM. Be light handed with those adjustments !

And so on, until you reach full RPM.

Billy603

Bert,

Since our gassers do heat quite a bit, would it be possible to ask Dave to add implement a temp factor in the solenoid curve, along with pressure and alt ?

Best regards

1967brutus

The engine temperature is barely of influence on the required mixture strength. When stone cold, it needs to be a bit richer, but that condition lasts only 10 or 15 seconds.
I have experimented quite a bit, but never been able to find a fixed correlation between engine temperature and mixture requirement.

What I have done, and which works "more or less, half of the time" is program 2 or 3 curves that are richer than standard (especially at the lower throttle regions) and I can activate those curves with a switch. I use them ONLY for cold starts, and I am not impressed with how well that functions, but for some engines it helps, other engines it appears to have zero positive effect.
I would not waste time on that.
What might be a good idea, is to set a full rich curve (100% valve opening) that activates at (for example) 135~140 deg CHT or something like that. It might protect the engine from overheating by letting it run rich for a few seconds.

Eastflight

Indeed, I think it will.

4dogspete

Hi Billy - Great Article: Now let's go from there... I need lots of help/advice on a DLE20cc and/or RCGF 20cc - both seem to have the same problems - unreliable. (Gotta be me??)
Mounted on a profile designed for a 20cc. Not great compression, but both start and runs OK. The following happened no less than 5 times in a row.
Start on the bench - tuned for what seemed like good running performance - Idles well, and transitions from low to medium to high on the bench. Held up - rotate around and inverted - runs just fine. Taxiied then took off and on the first turn - motor dies - crash.
Motor is mounted properly in the slot designed for it. Mounted the 260 ML fuel tank about the same horizontal position as the motor.. - plumbed with the yellow stuff and mounted on a piece of foam rubber with a felt clunk in the tank.
So far - lost 3 airplanes and rebuilt 2 - some rebuild 2 - 3 times. Remounted the DLE first then bought an RCGF 20cc - EXACTLY the same result.
Been flying for quite a few years - great with glows - 2-stroke and 4-strokes. Wanted to shift to gas - Bummer so far.
I'm convinced the problem is the installation, but I am at a loss - kind of tired rebuilding after a first short flight.

Any suggestions anyone?
PETE

Raleighcopter

your engines are probably going lean in the air. richen the upper needle slightly.

1967brutus

I would concur: Gassers have the nasty habit of needing to run slightly but noticably rich on the ground. At least, ALL mine do.
Never adjust a gasser on the ground (OK, of course you have to turn the needles when on the ground, but that is not what I mean...

Start out rich, , go fly, pay attention to how it runs in the air, land, and turn the HS needle 1/12th leaner, and go fly again. Pay attention to whether the engine improves or not. Keep repeating that as long as you notice improvement, the very moment you notice no difference, go back to the last setting that gave an improvement. If you notice a tendency to deadstick, ALWAYS first try the HS needle 1/6th further open to see if it cures it, if it does, you can carefully try and sneak up on "perfect", but ALWAYS judge that "perfect" in flight, never on the ground.

It's a base rule for gassers, they are a bit different than glow engines.

Billy603

Hi Bert,
With the TX16S I made 6 valve curves, from leaner to richer by 4% increments, applied on the beginning and the end of the curve.
With a simple button to push I can change the cruve and richness in flight.
This will allow to go quicker to find the latest final adjustment.
The Calmato has not yet flown because the gas reaching the crap trap dissolved the epoxy I had used to make it airtight.
So now I have put back a small standard glo reservoir with gas stopper, and am waiting for the weather to get better.

Keep you posted !

1967brutus

Not a bad idea, those multiple curves.

Epoxy should be gasoline resistant, but probably cannot handle the ethanol.

Proper installation of the fuel system really is of utmost importance.

Billy603

Hi all and Bert and Dave

Just to follow through:
* Tank choice: you must not use a tank which will not stand gas. The Glo ones (semi transparent, like the Kavans) are soft and will get even softer with time as gas is present. I had a perfectly going engine which went gradually worse with time and found the tank had got much too soft. The pressure from the exhaust pipe was upset by this softness.
Now I use the Dubro's and they are good. You can use the chinese transparent ones too, if you have room enough. They stay stiff. So use them both for the main tank and also the crap trap, for the same reasons.
Then, miracle, engine transitions are much better and everything is more predictable. Good.
* engine curve: I had some hard time with this one because the Thr position did not correspond to the carb opening position. So I got rid of it, Explanation is perhaps that the curve gives it a kind of expo shape, where the 3 last points (50% 75% 100%) had to deal with about half of the total opening. No good because not precise unless you have a valve curve with a lot more points than the 9 we advise. So, slow down the servo and get rid of the Thr curve.

Have a good time ! really worth it indeed !

1967brutus

I am assuming that the values you mention are on a range from 0 to 100%? If so, that indeed is a bit steep, my curves are usually a lot flatter than that.

My mechanical set-up aims for a linear and symmetric mechanical link from servo to carb. Meaning: servo arm length as identical as possible to the carb lever, and the levers "parallel and symmetrical". As in both being at a square angle to the linkage rod at the mid of the stroke.

I checked a few of my throttle curves, and they vary a bit, but the .91 fourstroke has as last three points (from -100 to +100) +24, +56 and +100
The .91 twostroke has +22, + 55, +100 as last three points
The .52 fourstroke has +19, +55, +100 as last three points
The 65 cc radial has +8, +49, +100 as last three points.

The other planes are similar as they have basically the same engines.

On average, my throttle curve seems to be (9 points, from -100 to +100) -100, -83, -67, -50, -30, -5, +24, +56, +100 as curve.

YMMV of course. I have had no issues with linear throttle curves with respect to getting the engines adjusted, but I did have issues with flying like that. I don't like a too agressive throttle with the stick all the way back, makes landing harder (my flying style basically is to pull the plane in on the engine, so I like a bit finer throttle control near the lower end.

I cannot comment on the tanks. For some reason, all tanks I have used so far all turned out to be gas resistant and not softening up over time. Usually I use what is in the plane when I get it, if I need to buy a tank however, it always is a Dubro. For some reason I really like those "chinned" tanks.

AA5BY

Hi to all,

Well, after 213 flights with a Saito 125 conversion, it went lean and this after 150 flights or so without a needle tweak which indicated something was amiss with the fuel system. The problem was quickly found to be the muffler pressure line had split and come off the muffler tap. It seemed a reasonably good time during winter to overhaul the entire fuel system.

Found was the muffler tap fitting was about 80% restricted and reamed out. The muffler itself had only a small amount of interior carbon and got wire brushed to quickly clean. Plugging the vent line and blowing into the fill line required a fair amount of lung pressure to produce a reasonable flow through the inline filter out the carb line. The filter was removed, and flow increased with less but still a fair amount of lung pressure needed. Thus the inline filter needed replaced and the likely source of remaining obstruction was the felt clunk, which will also be replaced.

The tank bung was stiff coming out and solidly formed so will need replaced. The pick up line was small Tygon and hardened. There was perhaps a half dozen floating specs of carbon in the remaining fuel in the tank.

The pressure line had not been filtered nor had a crap trap been used. Engine compression continues to feel good. Oil used is Stihl high performance (petroleum based) @ 20:1. Engine powers a 91" Cub.

Fuel lines, including pickup line will be replaced with Sullivan Pro Flex.

My one question is will the Pro Flex handle the heat at the muffler tap or should that be Viton?

Arlyn

1967brutus

As for the type of fuel line for the muffler connection: Easiest option is a sacrificial piece of regular Silicone fuel tubing (about 1" worth) connected to the tygon by means of a short piece of 3/32" or similar brass or aluminium tubing.
Silicone can't handle liquid gasoline, but is surprisingly resistant to heat or vapour, and these sacrificial pieces for me last anywhere between 2,5 and 5 years.
The better your fuel/air mixture, the longer it lasts, and that is not because of chemical action between the silicone and the unburnt fuel, but because the unburnt fuel burns in the muffler and raises the muffler temperature. The better the A/F ratio, the cooler the muffler runs.
This difference is remarkable: The oil I use does not bake on to the muffler, so my aluminium mufflers remain fairly clean,, but if the engine is running rich, the muffler gets hot enough for a fingerprint to burn in and also to deteriorate the silicone from heat. When the mixture (air/fuel) is correct, the silicone remains intact and fingerprints do not burn in. Heck, the latest engines That I set up from new, the header did not even really discolour.

And strangely enough, these really lean (near full stoiciometric) don't even rise cylinder head temperature too much. It is just a guess, but I think that a lot of the heat generated in the muffler afterburning a rich mixture, otherwise gets conducted back to the cylinder head. Any fuel not supplied to the engine, also cannot contribute to heat generation...