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Engine Design Project


Hiceadha
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Hi I'm new here and am about to start an engineering project for university where I' designing a small ultralight engine. I thought where is this more relevant then to flying. I have an interest in paramotors and would love to build one given the time and facilities hopefully in the near future.

As for the engine I was hoping to get some tips on what is already available in the market and whats wanted. If I link the design to paramotors then it will be a better project overall so given the chance to get any type of engine for your own diy project what would you want, 2-stroke, electric etc.? to give me an idea of whats wanted. Thanks

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Welcome to the Paramotor Club.

There are many engines for us to select from.

But to answer the 'what do we want' from an engine question.... the answer is simple :-)

Focus your efforts on (Power / thrust output to Weight)

SW :D

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Few off the top for me

• Horse power to weight ratio (how much HP can you give me in the lightest package)

• Zero vibration

• Low heat and motor with good heat dissipation

• Quite

• Good acceleration (Rapid RPM increase)

• Easy start

• 0 effect due to altitude

• Fuel efficient

Battery would be the best but current cell technology limits are slowing the development of a practical solution

2 stroke has been done to death (not sure what you can improve)

4 stroke is being tried but the problem becomes weight.

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One of the most successful paramotor engines ever produced is the Top80, compact lightweight, good power weight ratio, etc... relatively cheap, easily serviced, etc.... 2 Strokes have many advantages over 4 stroke- in terms of simplicity, but the price to pay is fuel economy.

Would be interesting to do a project to try and combine the benefits of 2 stroke with increased economy- replacing the carb and tuned pipe system with direct fuel injection- electronically controlling fuel metering and spark timing.....

GD

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Injection on a 2 stroker . What would the benifits be and what about the negatives.

Im not that good with engines but id be interested to know more about what could be acheived.

Basically with a 2 stroke direct injection you'd have a small lightweight compact engine that can be used in any orientation, a greater power to weight ratio than equivalent 4 stroke, and matching fuel economy of a 4 stroke.... On current 2 strokes with a tuned pipe system, upto 25% will pass straight through the engine/exhaust system unburnt when at full operating rpm. The extent of unburnt fuel varies depending on the engine setup and rpm... but generally it is accepted in 2 strokes.

With an accurate metering system and direct injection, this would eliminate excess fuel entering the combustion chamber- thus making the tuned pipe redundant, and increasing fuel efficiency.

On the downside- the injection system would be as complicated as the engine itself... and may end up heavy or bulky-- would also certainly need to be powered electrically..... This may be detrimental to engine reliability...

GD

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Well having had a good look at the website, that would indeed seem to hit the mark. But I wonder what resident engine tinkerer Spigot thinks of it.

Practical answer to increased power, economy and reliability or unreliable bling?

Very interesting! Didn't know a kit was available.

The video on the site shows it installed on a Top 80 too!

If it's reliable- then could be the way forward!!!!

The Top80 is light enough, but if you needed to carry less fuel- then there would be an increased weight saving!

GD

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I think it's half a solution :-/

EFI in this context is just a better carb that can or should tune itself to the conditions of flight, altitude temp etc

It still requires crankcase pressure and the tuned pipe to get the mixture in. Which is where we loose efficiency as Gordon pointed out so beautifully :-)

What we need is direct injection as used on modern Diesel engines.

Squirt a metered amount of fuel in after the piston has passed the exhaust port and bobs your mothers brother.

Sent from my iPhone using PMC Forum mobile app

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Getting back to engine requirements for flying:

1) Reliability.

2) Reliability (again, because in most powered flight, it is REALLY important.)

3) User friendliness (easy to operate, service and diagnose issues.)

4) Power/weight and other performance characteristics.

I believe this is a reasonable order of priorities for most of our flying.

For some types of competition, performance may come higher up the list.

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You need direct injection (injector in the head)

PROS

Fuel economy doubles

more power

emissions drop to equivalent four stroke

Smoother running

easier starting

no expansion chamber

no having to mess with carb settings

no fuel mixing needed

CONS

More electronics to go wrong

high pressure fuel pump needed

Air compressor needed (to atomise the fuel in the combustion chamber

Oil in to crank needs sorting

separate oil tank

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You need direct injection (injector in the head)

PROS

Fuel economy doubles

more power

emissions drop to equivalent four stroke

Smoother running

easier starting

no expansion chamber

no having to mess with carb settings

no fuel mixing needed

CONS

More electronics to go wrong

high pressure fuel pump needed

Air compressor needed (to atomise the fuel in the combustion chamber

Oil in to crank needs sorting

separate oil tank

Wow! I forgot about the expansion chamber also... definitely no need for this either....

Sounds like a nice idea- but the electrics would let the whole thing down I'm sure....

You cant beat a Top 80 with pull start for sheer simplicity!!!

GD

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The expansion chamber is an element of the tuned pipe (i'm ignoring silencing for the moment).

The list of pros and cons would suggest you are proposing not only direct injection, but a supercharged 2 stoke like the Commer TS3, Napier Deltic etc.

While this engine design does away with the oil in the fuel, it is not the lightest solution by a long way, especially as a small displacement single cylinder engine.

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You only need a supercharger if the air does not go through the engine.

The air is forced up in to the cylinder by the piston going down with the reed valves closed.

The expansion chamber is tuned to push as much of the fresh air/fuel mix back in to the cylinder that has passed straight through due to the open port design of the engine.

If fuel is injected after the ports are both closed then it cannot escape.

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