Jul 15, 2003, 03:00 AM Ed Cregger Ed Cregger Guest n/a Posts Re: 4-Cycle More Efficient? It depends. If you are limited to using over-the-counter engines from our hobby suppliers, then I would think that the four-stroke engines are a better choice for fuel economy. I do not believe that over-the-counter two-strokes will fare as well against an over-the-counter four-stroke. If you can have a custom made, direct fuel injection, oil injected two-stroke cobbled up, then the two-stroke might be a better choice. The two-stroke model diesel engine has two things going for it in that it is running a fuel that contains more calories per cc than glow fuel and it is running a higher compression ratio, which further increases power production and fuel efficiency. One advantage in using the largest engine possible is that the radio components remain essentially the same whether flying a small aircraft or a large aircraft. Thus, the R/C system becomes a smaller percentage of the aircraft's gross weight as the size of the model increases (with a limit of 1.2 cubic inches engine displacement in this example). This alone adds to the airframe's overall efficiency. We won't even get into the better Reynolds Numbers derived due to the increase in size. If one could fit an RCS/Moki 1.40 with a very lightweight magneto, one could have the best of all worlds - for a two-stroke. This two-stroke would sip less gas/oil mix than a glow four-stroke 1.20 and would provide more power while doing it at a lower gross weight (includes fuel load). This is just my opinion. Ed Cregger "H.J." wrote in message news:rMAQa.17061\$_K5.15278@fe01.atl2.webusenet.com ... > Trying to calculate which would fly FARTHER on a given amount of fuel in the > .61 to 1.2 cubic inch class engine.... > > Let's say the plane weighs about X lbs, and it carries Y c.c. of fuel, Which > would carry it farther, a 2C or 4C engine? > > Consider.... > A 4C has to waste energy on an exhaust stroke. > A 4C has less power than a 2C of the same displacement. > A 2C blows a lot of unburned fuel out the exhaust. > A 2C diesel is supposedly runs longer than a glow engine, but is that at > reduce power production? > > So, if the goal is to get the most range per unit of fuel, is a 2C or 4C > better? > > H.J. > > > >
 Jul 15, 2003, 03:00 AM mike tully mike tully Guest n/a Posts Re: 4-Cycle More Efficient? In my opinion (not worth much) the two stroke puts much unburned fuel out the exhaust. This is part of the reason motorcycle manufacturers gave up years ago on 2 stroke street bikes rather than try to find ways to make them comply with looming enviromental regulations (unburned hydrocarbons). Same reason you will start to see them disappear on snowmobiles and watercraft. In duration per cc of fuel, any methanol engine will be at a distinct disadvantage to a similar gasoline engine. Gasoline simply has much more energy per cc. Back in the eighties, Maynard Hill, multiple FAI world record holder set out to determine the absolute most efficient set up. The FAI at the time had a model aircraft engine displacement limit of 10 cc (.61 ci). Mr. Hill published a paper summarizing these studies with the American Institute of Aeronautics and Astronautics (you may want to look it up). He found that an 10 cc 4 stroke cycle model airplane engine with electronic ignition running on an exotic blend including gasoline, isobutane and synthetic oil was the optimum powerplant for his world record duration and distance pursuits.
 Jul 15, 2003, 03:01 AM M Dennett M Dennett Guest n/a Posts Re: 4-Cycle More Efficient? I'd say a two-stroke diesel, or a 4-cycle converted to ignition would be more optimal with the ultimate range coming from the 4c conversion. IIRC a transatlantic crossing was accomplished using an Enya(?) 1.20 4C converted to gasoline. The two stroke diesel may run at less peak horsepower than the same basic engine on glow, but runs significantly longer on a given volume of fuel due to the different fuel air ratio requiements. It will also turn more prop without baking to death and thus efficiency gains help offset 2C mileage issues. For range versus volume of fuel, you want gasoline or diesel fuel (if these are options for you) versus methanol and especially versus methanol plus nitromethane. If you were looking to gain the best range on 2 stroke glow, use a motor that will run on FAI or very low nitro fuel. Mike D. "H.J." wrote in message news:rMAQa.17061\$_K5.15278@fe01.atl2.webusenet.com ... > Trying to calculate which would fly FARTHER on a given amount of fuel in the > .61 to 1.2 cubic inch class engine.... > > Let's say the plane weighs about X lbs, and it carries Y c.c. of fuel, Which > would carry it farther, a 2C or 4C engine? > > Consider.... > A 4C has to waste energy on an exhaust stroke. > A 4C has less power than a 2C of the same displacement. > A 2C blows a lot of unburned fuel out the exhaust. > A 2C diesel is supposedly runs longer than a glow engine, but is that at > reduce power production? > > So, if the goal is to get the most range per unit of fuel, is a 2C or 4C > better? > > H.J. > > >
 Jul 15, 2003, 03:01 AM Grant Edwards Grant Edwards Guest n/a Posts Re: 4-Cycle More Efficient? In article , Ed Cregger wrote: > The two-stroke model diesel engine has two things going for it > in that it is running a fuel that contains more calories per cc > than glow fuel [...] Definitely true, but does diesel have more joules/gram than glow fuel? I suppose it only matters if amount of fuel is limited due to tank size or due to takeoff weight... -- Grant Edwards grante Yow! I wonder if I ought at to tell them about my visi.com PREVIOUS LIFE as a COMPLETE STRANGER?
 Jul 15, 2003, 03:01 AM The Natural Philosopher The Natural Philosopher Guest n/a Posts Re: 4-Cycle More Efficient? H.J. wrote: > Trying to calculate which would fly FARTHER on a given amount of fuel in the > .61 to 1.2 cubic inch class engine.... > > Let's say the plane weighs about X lbs, and it carries Y c.c. of fuel, Which > would carry it farther, a 2C or 4C engine? > > Consider.... > A 4C has to waste energy on an exhaust stroke. > A 4C has less power than a 2C of the same displacement. > A 2C blows a lot of unburned fuel out the exhaust. > A 2C diesel is supposedly runs longer than a glow engine, but is that at > reduce power production? > > So, if the goal is to get the most range per unit of fuel, is a 2C or 4C > better? > 4C almost always since the exhaust stroke that clears burnt gases is not the same as the inlet stroke that ingests new ones. All 2 strokes - except DI diesels - tend to throw unburnt fuel down the exhaust system. > H.J. > > > >
 Jul 15, 2003, 03:01 AM Arne Reil Arne Reil Guest n/a Posts Re: 4-Cycle More Efficient? The only way a 2 cycle can be sure of getting a full charge into the chamber is to blow some raw fuel out the exhaust before the piston closes the exhaust port...... i believe some of the newer (big) 2 cycles use an injection system to squirt the fuel in after the port closes...... and they are much cleaner, but not down to our level yet. .. Arne, CT, USA ========================= "mike tully" wrote in message news:20030714130945.28289.00000330@mb-m06.aol.com... > In my opinion (not worth much) the two stroke puts much unburned fuel out the > exhaust. .
 Jul 15, 2003, 03:01 AM The Natural Philosopher The Natural Philosopher Guest n/a Posts Re: 4-Cycle More Efficient? Arne Reil wrote: > The only way a 2 cycle can be sure of getting a full charge into the chamber > is to blow some raw fuel out the exhaust before the piston closes the > exhaust port...... i believe some of the newer (big) 2 cycles use an > injection system to squirt the fuel in after the port closes...... and they > are much cleaner, but not down to our level yet. Its called direct injection, and most full size diesels do it. Well most big ones anyway. > . > Arne, CT, USA > ========================= > "mike tully" wrote in message > news:20030714130945.28289.00000330@mb-m06.aol.com... > >>In my opinion (not worth much) the two stroke puts much unburned fuel out >> > the > >>exhaust. . >> > >
 Jul 15, 2003, 03:01 AM Pé Reivers Pé Reivers Guest n/a Posts Re: 4-Cycle More Efficient? 4-stroke gas engine like Ryobi!, or 4-stroke diesel conversion engine, if you have the skills. The mark II gas 1.60 MVVS with the 7mm carb is the most fuel efficient off the shelf airplane engine for the power I have ever tested, save for the Honda 4-stroke moped engine. My idea: Troll ?? -- Rgds, Pé From Arcen, South-East in the Netherlands preivers @ mvvs-nl.com http://mvvs-nl.com/ www.prme.nl "H.J." wrote in message news:rMAQa.17061\$_K5.15278@fe01.atl2.webusenet.com ... > Trying to calculate which would fly FARTHER on a given amount of fuel in the > .61 to 1.2 cubic inch class engine.... > > Let's say the plane weighs about X lbs, and it carries Y c.c. of fuel, Which > would carry it farther, a 2C or 4C engine? > > Consider.... > A 4C has to waste energy on an exhaust stroke. > A 4C has less power than a 2C of the same displacement. > A 2C blows a lot of unburned fuel out the exhaust. > A 2C diesel is supposedly runs longer than a glow engine, but is that at > reduce power production? > > So, if the goal is to get the most range per unit of fuel, is a 2C or 4C > better? > > H.J. > > >