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4 Strokes


Phil 9
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I think a lot depends on what sort of models you like flying & how you like flying them.....I like the sort of effortless way a 4 stroke goes about its business of hauling a model around (you will need a much bigger 4 stroke than a 2 stroke by the way......if you work on 50% bigger...ie replace a 60 2 stroke with a 90 4 stroke...you won't be far out!!)
 
Whereas 2 strokes always seem to be reving hard & making a lot of fuss a 4 stroke just gets on with the job.....
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Bit like my "Ruperts Dad " 60" span -Thick wing section-Looks a bit like a Druine Turbulent designed for a 52 'ish 4 stroke 'cos the designer Roger Groves was told that a 4 stroker wouldn't have enough whoomphh to power a 3-D job . Brilliant machine & on low rates is probably the best 2nd trainer around (ailerons) With a fine pitch prop it gets a bit noisier but will do absolutely anything & can be "braked" in a dive .The choice is yours . It's either a 12 X 6 or a12.5 X 3 3/4. Work that one out 'lecktrikly wise !
G-umpy 1
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  • 2 weeks later...
Posted by Martin Harris on 04/09/2009 21:43:21:
Also more fuel efficient and more acceptable sound to the neighbours, assuming you were referring to the slightly more realistic sound of a 4 stroke.

 I wouldnt say that they were more efficent. The smaller 52 size drink arund the same as a 46 2s but the bigger they go the more they drink. I have a YS110 that drinks 580cc in 13mins! A 90 2s would be more efficent but there is nowhere near the tourqe. If i was to make a bold statement i would say that 4 cycles are better than 2!

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Oliver,
 
You're not really comparing with an average 4 stroke here.  The YS is effectively fuel injected and typically runs on 25% nitro.  As you're no doubt aware, the nitro-methane "bulks out" the fuel, increasing the brake mean effective pressure - the effects being that the fuel is used much more quickly than the typical 0 - 10% nitro used by Laser, Enya, OS and clone 4 strokes etc. and of course, the YS is much more powerful capacity for capacity.

I would also take issue with your statement that a 52 4 stroke uses fuel at the same rate as a 46 2 stroke - all I can say is that in my experience none of my various OS and SC 52s use fuel at anywhere near the rate my OS or Irvine 46s.
 
By their very nature, 4 strokes are able to fill their cylinders better and burn more of the fuel passing through the engine.  Compare the temperature of their exhaust gas!  Tuned pipes will improve 2 stroke efficiency of course. Against 4 strokes is their extra weight and complication
 
I would always go for a 4 stroke in scale models and love their sound.  If I could justify the initial and running costs of a YS I'd love one and agree that they produce a terrific amount of power for their capacity. However, I also love the OS90 2 stroke in my Panic but I'm with you in that my natural preference is for 4 strokes!

Edited By Martin Harris on 24/09/2009 09:50:28

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A powerful 2 stoke is much cheaper to produce than a powerful 4 stroke for a given cc. using pushrods,  tappets and valve springs severely limits the peak rpm
chain or belt driven overhead cam would be better but still lacking in peak rpm
need to use the system where the valve has a  twin fork arrangement on the cam shaft  to open and close it, no valve spring at all , so delaying valve bounce to a much higher rpm , problem with going hitec is the engine may well have to be water cooled so the temperature can be finely regulated
point is would you pay a few grand for a 60 ?
dont know the ys 110, what is it, turbo or super charging certainly seems to be a cheap way of getting around the problem
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Well.....an OS26 fourstoke buggy motor will regularly hit 26,000 rpm.....250cc motorbike engines are often 4cylinder 4 stokes (62.5cc per cylinder) & they redline at 19-20,000 rpm.......how fast do you want to go???
 
2 strokes are generally more powerful than 4 stokes because you get twice the bangs....ie in any given time frame at the same rpm a 2 stroke will have twice as many power stokes as a 4 stroke....yes the combustion in a 4 stroke is more efficient etc but for power vs weight/complexity an air-cooled 2 stoke is hard to beat....that's why we use 'em!!!
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