vvrc 40cc twin
05-14-2014, 08:54 AM
#53
Senior Member
This got me thinking, as I switched over to the Stihl Ultra. So I shot an email off to Stihl to get their opinion. This is the reply I got. Very interesting. This would seem to be the real issue with pump gas, and why it may be a good idea to use something else. (avgas, white gas)
"Mr. Perry,
Thank you for your email. The shelf life of our engine oil before it is mixed (sealed or unsealed) is approximately five years. Once the fuel is mixed, the oil itself does not necessarily degrade any faster. It is actually the gasoline in the fuel mixture that deteriorates long before the oil. Today’s gasoline is formulated to operate best in automobiles with the expectation that the fuel will be used within 3 weeks to a month after it is sold. Gasoline companies do not take small engine products into account when designing fuels. For this reason STIHL and other manufacturers recommend that fuel mix over 30 days old is not used in small engine equipment. Gasoline consists of chains of hydrocarbon molecules of various lengths. As the fuel ages the lighter chemicals in the fuel evaporate out. In addition the remaining components can combine into other chemicals. For example you may have heard the term, "the fuel has varnished". Basically the fuel at this point is less combustible and burns abnormally in the engine. Since the fuel isn't actually "gasoline" any longer, it doesn't burn completely and you are left with fuel and mix oil residue in the engine. In most cases the engine will not operate long enough to cause severe damage since the residue will cause the rings to stick, the engine will lose compression, and will not start. This ‘varnished’ fuel also does damage to the internal parts of the carburetor often damaging it beyond repair. Normally, the only option to correct this problem is a re-build or, more likely, replacement of the carburetor as well as a possible fuel line replacement and complete engine clean-out if the problem is severe. This is issue can be avoided by draining out the unit and running it until the engine runs out of fuel if the saw is going to be stored for more than 30 days. If you prefer to have fuel in the unit in case of an emergency, we suggest a stable fuel such as our STIHL MotoMix which has a two year shelf life once the can is opened and does not have the harmful additives pump gasoline contains. Drain the fuel from the tank and add a little bit of MotoMix. Start the unit and allow it to run for a couple minutes to get the fuel through the fuel system. This is the method I personally use and it has been very successful. I hope this is helpful and please let me know if I can be of any further assistance. Thanks again."
Or maybe do as they say and run that motomix, sort of like an after run oil we are used to, before putting up our planes for the winter. Might save some maintenance grief down the road.
"Mr. Perry,
Thank you for your email. The shelf life of our engine oil before it is mixed (sealed or unsealed) is approximately five years. Once the fuel is mixed, the oil itself does not necessarily degrade any faster. It is actually the gasoline in the fuel mixture that deteriorates long before the oil. Today’s gasoline is formulated to operate best in automobiles with the expectation that the fuel will be used within 3 weeks to a month after it is sold. Gasoline companies do not take small engine products into account when designing fuels. For this reason STIHL and other manufacturers recommend that fuel mix over 30 days old is not used in small engine equipment. Gasoline consists of chains of hydrocarbon molecules of various lengths. As the fuel ages the lighter chemicals in the fuel evaporate out. In addition the remaining components can combine into other chemicals. For example you may have heard the term, "the fuel has varnished". Basically the fuel at this point is less combustible and burns abnormally in the engine. Since the fuel isn't actually "gasoline" any longer, it doesn't burn completely and you are left with fuel and mix oil residue in the engine. In most cases the engine will not operate long enough to cause severe damage since the residue will cause the rings to stick, the engine will lose compression, and will not start. This ‘varnished’ fuel also does damage to the internal parts of the carburetor often damaging it beyond repair. Normally, the only option to correct this problem is a re-build or, more likely, replacement of the carburetor as well as a possible fuel line replacement and complete engine clean-out if the problem is severe. This is issue can be avoided by draining out the unit and running it until the engine runs out of fuel if the saw is going to be stored for more than 30 days. If you prefer to have fuel in the unit in case of an emergency, we suggest a stable fuel such as our STIHL MotoMix which has a two year shelf life once the can is opened and does not have the harmful additives pump gasoline contains. Drain the fuel from the tank and add a little bit of MotoMix. Start the unit and allow it to run for a couple minutes to get the fuel through the fuel system. This is the method I personally use and it has been very successful. I hope this is helpful and please let me know if I can be of any further assistance. Thanks again."
Or maybe do as they say and run that motomix, sort of like an after run oil we are used to, before putting up our planes for the winter. Might save some maintenance grief down the road.
Avgas has a nice smell to it. No auto gas stench (which I really can't stand and neither can my wife).
Avgas has yet to cause ANY deterioration of the rubber parts in my carbs. Very compatible with same, probably for the same reason as above with full scales. Also, I'm finding that as I recommission certain engines after storage (2 years at least) they start right up and produce the same power as I remember.
To me, Avgas positives outweigh the negatives by a wide margin.
05-14-2014, 01:44 PM
#54
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Thanks Matt, I think I will try this out too. I pass the local airport on the way to the field, so how convenient is that to have gas available just a couple miles to or from the field!
The smell is a bonus too, and worth the extra couple bucks a gallon if you ask me! Anyway, thanks for that! I have a couple gallons of my usual ethy free 'clear gas' to burn up first, and will give the real avgas a try.
Are there different octane's as well, or what? Anything to look out for, to or not to get from someone never having been to the airport gas pump?
The smell is a bonus too, and worth the extra couple bucks a gallon if you ask me! Anyway, thanks for that! I have a couple gallons of my usual ethy free 'clear gas' to burn up first, and will give the real avgas a try.
Are there different octane's as well, or what? Anything to look out for, to or not to get from someone never having been to the airport gas pump?
05-14-2014, 11:39 PM
#55
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A couple of years ago you said you got 500-600 rpm stronger performance with automobile gas versus avgas. This was with the GT33. The GT33 in your 11 pound plane can afford to lose 500 rpm but in some applications that is a lot to give up. 500 rpm on a 20" prop is not insignificant. I expect the vvrc 40 will turn roughly similar props.
You point out some attractive reasons to use avgas but there is no reason not to tell the whole story.
MTK's avgas vs auto gas comparision is here
www.rcuniverse.com/forum/gas-engines-142/11005338-100-octane-aviation-fuel-gasser-6.html#post11036660
You point out some attractive reasons to use avgas but there is no reason not to tell the whole story.
MTK's avgas vs auto gas comparision is here
www.rcuniverse.com/forum/gas-engines-142/11005338-100-octane-aviation-fuel-gasser-6.html#post11036660
Last edited by aerobear; 05-14-2014 at 11:44 PM.
05-15-2014, 06:15 AM
#56
Thanks Matt, I think I will try this out too. I pass the local airport on the way to the field, so how convenient is that to have gas available just a couple miles to or from the field!
The smell is a bonus too, and worth the extra couple bucks a gallon if you ask me! Anyway, thanks for that! I have a couple gallons of my usual ethy free 'clear gas' to burn up first, and will give the real avgas a try.
Are there different octane's as well, or what? Anything to look out for, to or not to get from someone never having been to the airport gas pump?
The smell is a bonus too, and worth the extra couple bucks a gallon if you ask me! Anyway, thanks for that! I have a couple gallons of my usual ethy free 'clear gas' to burn up first, and will give the real avgas a try.
Are there different octane's as well, or what? Anything to look out for, to or not to get from someone never having been to the airport gas pump?
05-15-2014, 07:32 AM
#57
It would seem that buying more than a gallon at a time would also be prudent when going to the airport. Problem is, my can is only one gallon, so I would have to figure something out here. Trick is, measuring exactly a gallon to pour into my can. I need a flow meter on my funnel! I think I would like to buy 5 gallons at a time, but to me, my 1 gallon can for the flight line is way more convenient.
05-15-2014, 08:29 AM
#58
Senior Member
Thanks Matt, I think I will try this out too. I pass the local airport on the way to the field, so how convenient is that to have gas available just a couple miles to or from the field!
The smell is a bonus too, and worth the extra couple bucks a gallon if you ask me! Anyway, thanks for that! I have a couple gallons of my usual ethy free 'clear gas' to burn up first, and will give the real avgas a try.
Are there different octane's as well, or what? Anything to look out for, to or not to get from someone never having been to the airport gas pump?
The smell is a bonus too, and worth the extra couple bucks a gallon if you ask me! Anyway, thanks for that! I have a couple gallons of my usual ethy free 'clear gas' to burn up first, and will give the real avgas a try.
Are there different octane's as well, or what? Anything to look out for, to or not to get from someone never having been to the airport gas pump?
The only thing to note is the fact that Avgas reduces the peak RPM by a few hundred as compared to PREMIUM auto gas. In my application I NEVER EVER have to use full throttle so it is a moot point. BUT that may mean something to those that must use full throttle for the whole flight
Last edited by MTK; 05-15-2014 at 08:34 AM.
05-15-2014, 08:53 AM
#60
Senior Member
A couple of years ago you said you got 500-600 rpm stronger performance with automobile gas versus avgas. This was with the GT33. The GT33 in your 11 pound plane can afford to lose 500 rpm but in some applications that is a lot to give up. 500 rpm on a 20" prop is not insignificant. I expect the vvrc 40 will turn roughly similar props.
You point out some attractive reasons to use avgas but there is no reason not to tell the whole story.
MTK's avgas vs auto gas comparision is here
www.rcuniverse.com/forum/gas-engines-142/11005338-100-octane-aviation-fuel-gasser-6.html#post11036660
You point out some attractive reasons to use avgas but there is no reason not to tell the whole story.
MTK's avgas vs auto gas comparision is here
www.rcuniverse.com/forum/gas-engines-142/11005338-100-octane-aviation-fuel-gasser-6.html#post11036660
Hey might as well state the rest of the story of the GT33. It is a piped set-up using the ESComposites 40G pipe. I have used both the 30G and 40G and results are the same. That's the reason why you can only buy the 35G from Ed Skorepa, Mr. ES Composites currently. No need to carry multiple pipes if one will give you identical results in this engine displacement size (30cc to about 45cc). The length I use, exhaust flange to reflector baffle in the pipe, is 27". I've tried as long as 31" and the results were not any different. This is not a glow engine that needs a narrow tuning length to operate properly and it doesn't depend on this tune to time the ignition. BUT the pipe does improve RPM and most importantly Torque, over the muffler.
I use Bel Ray MC-1 Motorcycle Racing Synthetic at 50:1 in my Avgas. I use the same mix for break in as regular running. Sure it takes as many as 4 gallons to fully break in, but so what? Time at the field is well spent.
Lessee, anything else? Oh yeah, the GT33 spools up great running larger loads. The current one I'm using is my own design wood-carbon hybrid 20 1/4 x 12. Why go through thetrouble? Well, the wood-carbon hybrid weighs 77 grams while a similar APC 20 incer weighs 170 grams. The OS GT33 has a longer stroke than all of other 30cc class engines currently available and that's a major reason it can turn bigger lumber. The generated noise has to be heard to be appreciated. I have a couple vids on Utube that showcase the noise footprint quite well (Near whisper quiet)
I believe the 40 twin will turn this prop also but I have not tried it. I intend to run the 40 twin on a pair of 26G pipes also but I haven't gotten around to ordering the set from Ed yet. I don't have a plane for it yet so it can wait.
Last edited by MTK; 05-15-2014 at 08:56 AM.
05-15-2014, 10:45 AM
#62
It would seem that buying more than a gallon at a time would also be prudent when going to the airport. Problem is, my can is only one gallon, so I would have to figure something out here. Trick is, measuring exactly a gallon to pour into my can. I need a flow meter on my funnel! I think I would like to buy 5 gallons at a time, but to me, my 1 gallon can for the flight line is way more convenient.
05-15-2014, 12:07 PM
#63
Senior Member
I buy two 5gallon cans full at a time. I have a 2 gallon field can, I mix 1 gal at a time in a clear 1 gal bottle and pour that into the field can. I have 111cc 55cc 35cc and 20cc gassers. With the clear 1gal bottle I pour in oil then fill to the same point each time.
05-15-2014, 01:20 PM
#65
Ron I buy my avgas in 5 gallon quantities too. MC-1 comes in convenient 12.8 ozs bottles. One bottle per 5 gallons is 50:1 so I mix the whole thing in one shot. 5 gallons used to last about 2-3 months but lately, with "old age" making a rude appearance, I don't get out as often as I want to. My hands and wrists have gotten so rickety, I can't hardly hold the TX AND tickle the sticks at the same time. KRAP!!! Can I say that??? or will RCU police fine me
05-15-2014, 03:50 PM
#66
I will look into this bulk gas buy thing. Not sure I want that much gasoline in my garage, but I will ponder it. I sure hate the smell of pump gas. One of the things that always turned me off when I started up with the gassers. I have also found gasoline to be more toxic to finishes/paint etc. Not the exhaust like glow fuel, but if raw gas gets on anything. The oils are really aggressive as well compared to glow. Have you guys noticed any less toxicity with the avgas? Like maybe some of the additives in the pump gas causing some of the problems?
05-15-2014, 04:37 PM
#67
I will look into this bulk gas buy thing. Not sure I want that much gasoline in my garage, but I will ponder it. I sure hate the smell of pump gas. One of the things that always turned me off when I started up with the gassers. I have also found gasoline to be more toxic to finishes/paint etc. Not the exhaust like glow fuel, but if raw gas gets on anything. The oils are really aggressive as well compared to glow. Have you guys noticed any less toxicity with the avgas? Like maybe some of the additives in the pump gas causing some of the problems?
05-15-2014, 07:17 PM
#68
Senior Member
I will look into this bulk gas buy thing. Not sure I want that much gasoline in my garage, but I will ponder it. I sure hate the smell of pump gas. One of the things that always turned me off when I started up with the gassers. I have also found gasoline to be more toxic to finishes/paint etc. Not the exhaust like glow fuel, but if raw gas gets on anything. The oils are really aggressive as well compared to glow. Have you guys noticed any less toxicity with the avgas? Like maybe some of the additives in the pump gas causing some of the problems?
You may think of avgas as a slower evaporating solvent like various other things we use in this hobby. I doubt it is better or worse. It contains a little lead so it's not a good idea to sniff the exhaust chronically and continuously over a long time. That's about all the precaution I take
I have spilled it on painted fuses and haven't seen any adverse effects. But that's on well cured and dried paint. Fresh paint might be a different story. And I'd rather not find out. On the other hand, high nitro glow fuel (20+ %) seems to me to be more aggressive. BTW some of the better cleaner for the slight exhaust oil we get after a session is Simple Green. I dilute the concentrate 50% and it works super.
05-17-2014, 05:57 AM
#69
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Since we are on a gas kick at the moment... the Chevron here started carrying ethy free gas, they call clear gas, and also the 100 and I think 110LL for off road use, they claim. Now I wonder if that is an equivalent to AvGas, the same as, or if its different stuff all together? I can't imagine the Chevron selling AvGas, but it does sound like it.
I was getting the good 'clear gas' from a local solvent supply that sells racing fuel (aka clear gas), and since Chevron is on way to the field, I started getting it from there.. its a slight different smell than the solvent place though, even though they seem to be claiming its the same stuff.. it cant be.
Anyone know what Chevron is up to?
I was getting the good 'clear gas' from a local solvent supply that sells racing fuel (aka clear gas), and since Chevron is on way to the field, I started getting it from there.. its a slight different smell than the solvent place though, even though they seem to be claiming its the same stuff.. it cant be.
Anyone know what Chevron is up to?
05-17-2014, 10:45 AM
#70
When I was first learning about gas model airplane engines, the guys running them raved that it was the way to go, at the field and on the forums. I agree that they are the way to go, as all of my new aircraft for the most part are gas powered.
That being said, one of the things that was very misleading is that gas does not effect you finished plane, and that fuel proofing was not needed. Well this is wrong. The exhaust of gas is cleaner than glow, so that aspect does not need to be fuel proof. Raw gasoline on your finish, in my experience tends to be more aggressive than average, 15% glow fuel. So, Fuel proofing is required with both fuels where the presence of unburned fuel is an issue.
The big difference in my experience is that gas powered planes tend to be bigger. Bigger planes are not effected by exhaust as much as smaller planes. Also, glow engines tend to throw unburned fuel out the exhaust. Especially as so many run them rich. This will not be nice to your finish either.
It took me a couple of years to learn the full differences between the 2 types of fuels. Fuel proofing is required for both, but the exhaust aspect has a different effect.
That being said, one of the things that was very misleading is that gas does not effect you finished plane, and that fuel proofing was not needed. Well this is wrong. The exhaust of gas is cleaner than glow, so that aspect does not need to be fuel proof. Raw gasoline on your finish, in my experience tends to be more aggressive than average, 15% glow fuel. So, Fuel proofing is required with both fuels where the presence of unburned fuel is an issue.
The big difference in my experience is that gas powered planes tend to be bigger. Bigger planes are not effected by exhaust as much as smaller planes. Also, glow engines tend to throw unburned fuel out the exhaust. Especially as so many run them rich. This will not be nice to your finish either.
It took me a couple of years to learn the full differences between the 2 types of fuels. Fuel proofing is required for both, but the exhaust aspect has a different effect.
06-08-2014, 05:28 AM
#73
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Ive had one for abought 3 months now and I just love it. I havn't had to change a needle setting from when it came from the store this is my sixth gaser and the best one yet overall.