Two Stroke vs. Four Stroke Engines | 2 Cycle vs. 4 Cycle | Powered Parachutes | Easy Flight
Автокөліктер мен көлік құралдары
I’ve encluded a video that shows an animated two stroke combustion engine and how it works. The animation came from:
savree.com/en/product/two-stroke-engine/
Thanks so much to the creator for producing the animation and allowing me to use it!
Powered parachutes -and for that matter all aircraft- are concerned with weight and power and reliability. Powered parachutes are particularly power-hungry, though. That has to do with the relatively inefficient nature of our wings. That means that both two-stroke and four-stroke engines have very appealing features.
A stroke is when a piston goes either up or down in an engine cylinder. A cycle is part of the critical process of getting fuel and air into the engine and getting power out of it. Each cycle happens very rapidly in a four-stroke and even more rapidly in a two-stroke.
The Intake starts the process. For a four-stroke engine, this stroke of the piston begins at the top dead center (which is the highest the piston can go up) and ends at the bottom dead center. In this stroke the intake valve must be in the open position while the piston pulls a fuel-air mixture into the cylinder by producing a vacuum in the cylinder through its fast, downward motion. So the piston is moving down and the fuel-air mixture from the carburetor is being sucked in by the downward motion of the piston.
The Compression stroke begins at bottom dead center, or just at the end of the intake stroke, and ends at top dead center. In this stroke the piston compresses the fuel-air mixture in preparation for ignition during the power stroke. Both the intake and exhaust valves are closed during this stage.
The Combustion stroke is the start of the second revolution of the four-stroke engine. While the piston is approaching top dead center -near the end of the compression stroke- the compressed fuel-air mixture is ignited by a spark plug -or two- forcefully pushing the piston down to bottom dead center. It produces the mechanical work from the engine by forcing the crankshaft to turn.
During the exhaust stroke, the piston makes the trip up from bottom dead center to top dead center to clear out the bad air. This time, the exhaust valve is open. The piston pushes the spent fuel-air mixture past the exhaust valve, into the exhaust system and ultimately back to the atmosphere.
A two-stroke engine has only two strokes. One upstroke and one downstroke. How it works is that a two-stroke engine combines the compression and ignition cycles on its upstroke while combining the power and exhaust cycles on the downstroke.
During the Intake/Compression stroke: the piston moves up, draws fuel-air mixture in AND compresses it.
During the Combustion/Exhaust stroke the fuel is ignited, the piston is forced down, AND the exhaust is ultimately pushed out.
The big question becomes, why should we care about two-strokes and four-strokes?
First there is expense.
And as we get into this comparison, it makes sense to point out that over ninety percent of two-seat powered parachutes use Rotax engines.
Therefore it makes sense to focus on those engines for the sake of this discussion.
The most commonly used Rotax two-stroke, the Rotax 582 with a Model E gear box, costs over $8,000 retail.
The most commonly used Rotax four-stroke, the Rotax 912ULS costs over $21,000 retail.
If you consider that most of the powered parachutes available used have used Rotax 582 engines on them, that makes the price of a two-stroke powered parachute even more reasonable.
The power delivered by the Rotax 912 ULS is impressive.
100 hp. The Rotax 582 is 65 hp.
The Rotax 912 ULS weighs approximately 143 lbs.
The Rotax 582 with an E gearbox is about 104 lbs.
That means with the 912 ULS, you’re going to get about .7 horsepower per pound of engine. With a 582, you’re only getting .6 horsepower per pound.
Part of the value of an engine is how long it lasts. Time between overhaul favors the Rotax 912 ULS. A new engine can be run for 1,500 hours or twelve years.
ALL of the Rotax two-stroke engines are only good for 300 hours or five years.
Yes, that means that the Rotax 912 ULS will run five times longer before you need to overhaul it.
Then there are reliability issues.
Now the common knowledge is that two strokes fail more often than four strokes.
Four-strokes are known for being much more fuel efficient, but that seems to be a wash with two-stroke powered parachutes vs. four-stroke powered parachutes.
A big edge to powered parachutes using two-strokes is the nimbleness of the machines. Lighter often equals more fun.
Learn how to fly at www.easyflight.com
Roy's Powered Parachute Book: www.poweredparachutebook.com
#easyflight #flying #poweredparachutes #pilot #aviation #aircraft #lightsportaircraft #flighttraining #learningtofly #parachute #engines
Пікірлер: 38
Looking forward to an episode about PPC wings: rectangle vs elliptical.
@EasyFlight
3 жыл бұрын
That will be fun... and probably controversial!
@wkboggs5
Жыл бұрын
Agreed. But for me, the stability and flight characteristics/security of the rectangle wing is the way to go. I like to take my kids up and I don’t generally do much “agility” type movements. I really enjoy the “best seat in the house” calm views. Just my $.02.
I have flown a 582 in my trike for 20 yrs without any engine failures. My first engine had 540 hours on it before I decided to sell it. I am on my 3rd engine and have over1,100 flight hrs time.🤓
@EasyFlight
Жыл бұрын
Hi Timm! Great to hear from you. I love the Rotax 582!
Thank you for the video 💪🏼
Great video, Roy! Thanks so much.
@EasyFlight
3 жыл бұрын
You are so welcome! Thanks for the feedback!
As I'm making plans ($$$!) to purchase a powered parachute, this video is very helpful to me. Thank you Roy.
@EasyFlight
3 жыл бұрын
It's a big investment. Boy do I know. I've gotten two of them in the last couple of years to do training!
I miss my paraplane - need to get some money again and fix it - thank you for this
@EasyFlight
2 жыл бұрын
You do need to get that Paraplane flying! Good, inexpensive fun!
Thank you so much for your invaluable information, highly appreciate it, have a great day, keep it up the outstanding job.
@EasyFlight
3 жыл бұрын
So nice of you. Thanks!
What's the cost to overhaul a four cylinder? And what's the cost to overhaul a 2-cylinder engine
@EasyFlight
Жыл бұрын
I believe the general rule of thumb is about half of the cost of a new engine.
I'm so interested in the sport!
@EasyFlight
Жыл бұрын
It is a great sport. You need to give it a try.
How about noise level? Are the 4 strokes quieter?
What? An overhaul on a Rotax 503 or 582 is $4,000. Where did you get those crazy figures? Try $400. New rings, wrist pin bearings and a general good clean is all it takes. If absolutely necessary maybe a couple of pistons.
@EasyFlight
3 жыл бұрын
Good question. But you aren't talking about a true overhaul if that is all you are doing. For an overhaul, Rotax mandates that you need a few more parts than you listed. The parts alone will cost $2,000. (lockwood.aero/parts/two-stroke-parts/582ul/582-repair-kit.html?___SID=U). A thousand for labor. The rest is just engine removal, transportation to and from the service center, and reinstallation. You can save money by rounding corners on parts and doing the work yourself, but I'm just trying to be as honest about costs as I can be. Thanks for commenting!
@talusranch990
2 жыл бұрын
Run
How do we call this thing you’re flying?
where do you located in Florida and how much you charge for lesson PPG PPC how long it will take to get the license how much it will cost to get the license
@EasyFlight
Жыл бұрын
Hi John! I operate out of the Dunnellon Airport in Florida and the Greenville Airport in Illinois. If you would like to talk about getting your license, you should begin by visiting /www.easyflight.com.
The 2 stroke engine weighs much less than a 4 stroke but it burns fuel almost twice as fast as the 4 stroke. That's because in a 2 stroke one (every) revolution of the crankshaft/propeller contains a power stroke which uses fuel while a 4 stroke has one power stroke per two revolutions of the crankshaft/propeller. With a 4 stroke you're using fuel on one revolution but getting 2 revolutions of power. So you will have to carry about twice the amount of fuel in a 2 stroke to get the same run time as a 4 stroke. Fuel weighs about 6 pounds per gallon, the weight of the extra fuel you must carry in the 2 stroke will negate much of the lower weight advantage of the 2 stroke engine itself.
@EasyFlight
3 жыл бұрын
Excellent points! The only reason people typically go for the two strokes now is responsiveness and price.
@ulbuilder
2 жыл бұрын
What assumptions have you made to reach this incorrect conclusion? If a given aircraft requires say 50hp at cruise speed, it requires 50hp no matter if it is powered by a 2 or 4 stroke. If both engines are producing the same power output then the fuel consumption will be nearly identical with the two stroke using just a tiny bit more fuel because they are typically run slightly rich. Think about it like this, let's say you have a 100cc 4 stroke and a 100cc 2 stroke both spinning at 1000rpm. Yes the two stroke will consume twice the fuel compared to the 4 stroke, but it would also be producing about twice the total power too! If you slowed the 2 stroke to 500rpm the power output and fuel consumption would be nearly identical to the 4 stroke at 1000rpm. Bottom line, a 4 stroke is absolutely not twice as efficient over a two stroke so it's impossible for it to consume half the fuel and produce the same amount of total power output.
@martinpoleski1204
2 жыл бұрын
@@ulbuilder for a given engine rpm a 4 stroke only fires (using up a cylinder full of fuel/air mix) half as many times as a 2 stroke engine. So at 4,000 engine rpm a 4 stroke will fire 2,000 times while a 2 stroke will fire 4,000 times thus it would appear that at 4,000 engine rpm the 4 stroke would be using twice as much gas. However you are correct in that engine rpm/fuel economy does not equate to engine horsepower/fuel economy. And technology now indicates that the engine horsepower/fuel economy of 4 strokes and modern 2 strokes is near equal.
@martinpoleski1204
2 жыл бұрын
sorry, please correct above to read:"...thus it would appear that the 4 stroke would be using half as much gas."
@ulbuilder
2 жыл бұрын
@@martinpoleski1204 The fuel consumption and power output is directly related to displacement. A 100cc 4 stroke at 4000 rpm displaces 100cc x (4000rpm/2) = 200,000cc of fuel air mixture per minute A 50cc 2 stroke at 4000rpm displaces 50cc x 4000rpm = 200,000cc of fuel air mixture per minute. Both produce about the same power and consume the same amount of fuel. The two stroke is lighter because its a smaller less complicated engine and it makes the same power as the 4 stroke because it fires twice as often as the 4 stroke.
If the FAA had a modicum of concern for the environment and the safety of Part 103 pilots...er...operators, it would increase the weight allowances for ultralights to allow them to use heavier, more reliable, less polluting four-stroke engines; but most are too cowed by our present authoritarian federal government to suggest change, out of fear of regulatory revenge.
@EasyFlight
Жыл бұрын
Suggestions have been made. The problem is that the FAA has said that if Part 103 was opened up for review that we might lose the whole thing. Keep in mind that even drone pilots need to get pilot certificates now. Ultralight pilots and parachutists are some of the most free pilots in America.
Stop with the bell
@EasyFlight
Жыл бұрын
LOL. Thanks for the suggestion!
Art of making up confusion out of nothing... "Cycle" is the repeating pattern as a whole. We're talking about a 4-stroke cycle or 2-stroke cycle. If you don't like the word "stroke" you can replace it with "phase" or "stage" or "move" etc. but definitely not "cycle".
Look at offroad motorcycles bud....its all 4