ORIGINAL: DagTheElder
DaveR
I'm sure the technical difficulties are daunting, but what choice does YS really have? If YS wants to continue in the model engine market, they better figure out how to make a gas engine in the next few years, or they will be bankrupt and without a market like Kodak.
Can it be done by YS to produce an equal powerful engine running on petrol with the same physical dimentions as theirs methanol/mix engines? I do not think so, but if they do it, horray I was wrong.
I will try to substansiate the above. (Some math will be necessary to explain this)
2 and 4 stroke engines.
4 stroke Volume svept= n cylinders x pi/4xbore sq x lenght stroke
2 stroke, if the exhaust port closes some distance before tdc (top dead centre) then the trapped svept volume is:
2 stroke Volume trapped = n cylinders x pi/4 x bore sq x lenght stroke
This volumes can produce the work:
2 stroke Work indicated = imep x volume svept x rps
4 stroke Work indicated = imep x volume svept x rps/2
(imep = Indicated mean effective pressure)
(rps =revolutions per second)
Interpretation of the last one. A 4 stroke engine of equal power of the two stroke (Work indicated), with equal svept volume must have an imep value that is double of the two stroke engine. One can play with these three factors but the end result should be the same. Question, how practical will it be with a 4 stroker reving 16-20'?
I hope this will help to understand why i donot think a 4 stroke petrol engine will be as powerful as a methanol/mix engine compared as apple to apple. YS can make their engine more powerful by increasing svept volume and so on but that will be a totally different engine.
The YS 4 stroker really is a fantastic powerful engine running on methanol/mix. The CDI has the advantage that it donot need a lot of fuel to correct the ignition timing as glow need.
Hope I did not offended someone.
Best regards
Largely I agree with you, tha it is diffuclt for a 4 stroke MeOH engine to transfer to pertrol power and maintain dimensions. However it is a design problem so I won't be writing anything off just yet.
2 strokes have some inherant drawbacks, poor cylinder scavenging being one and failry low compression ratio is another. Four srokes have them trumped here.
The really big issue with petrol engnes is that very very few have been designed for the RC hobby. I believe the DLE20 is the first and for teh first time theres a petrol option that delivers performance lsoe to its MeOH equivalant (OS 120AX).
Any engine takes time and money to develop and with the RC hobby being small once a design is into production only incremental changes are made till the initial investment is recouped and a new design is started.
OS GT33 is the next purpose built RC hobby engine I.e. not one that has a development history dating back to a botany implement.
What MeOH Rc engine have on petrol engines is 50 years more development for a very specialised market. And typically the engine as been designed in conjunction with its exhaust to achieve best results.
UAV'sare going to push petrol engines forward and then we'll see what potential really exists.
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