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4 stroke petrol engines


Phil 9
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I have seen Saito fs petrol engines advertised and like the idea of a fs petrol.
 
does anyone have experiance of these engines.
 
does anyone else produce fs petrol
 
they are expensive though would a nitro fs be better.
 
although expensive i think it may be an investment that would last years and a few airframes but there are not a great range in sizes. there is a 20cc engine but would be enough power for a 120 model?
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Phil, you can convert a glow four stroke to run on petrol with a kit from just engines amongst others for around £50. So pretty much any sized engine you would like to have.
 
The main thing is that a petrol motor uses less fuel so the additional weight of the CDI unit & batteries is offset by you not having to carry so much fuel.....very relevant as the engine size gets above 10cc or so!!!
 
Petrol engines also need less oil in the mix so you don't get lots of oil over your model.
 
Not done a conversion myself although it is on the to-do list when I have the time & money (2030 maybe ??) but there are lots of people who have.....I'm sure someone will pop up soon....
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I have a Saito FG-14B 14cc 4-stroke petrol fitted in my Hangar 9 Sopwith Camel. It runs beautifully, idles perfectly at 1900rpm and sounds superb but it wasn't cheap! It hauls the 5Kg airframe around no bother at half throttle. They also do larger sizes here . Unlike my Zenoah 20 2-stroke petrol which uses a 40:1 oil mix the Saito needs a 20:1 mix and it also has a total loss crankcase breather so there is a bit of black oil spattering along the fuse but nothing like the sticky muck from glow fuel. I don't use a muffler on the Saito just an 90deg knuckle and a 12" length of bendy pipe (from J'en) so the exhaust note has a wonderful bark to it. I've only been able to run the engine for a couple of hours so it can only get better
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I have seen Roto engines advertised before. No doubt they are very good, they certainly look good, but the word roto means 'broken' in Spanish.
 
I wouldn't think that they sell many in Spanish speaking countries.
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Posted by Steve Hargreaves on 12/07/2011 11:06:48:
Phil, you can convert a glow four stroke to run on petrol with a kit from just engines amongst others for around £50. So pretty much any sized engine you would like to have.
 
The main thing is that a petrol motor uses less fuel so the additional weight of the CDI unit & batteries is offset by you not having to carry so much fuel.....very relevant as the engine size gets above 10cc or so!!!
 
Petrol engines also need less oil in the mix so you don't get lots of oil over your model.
 
Not done a conversion myself although it is on the to-do list when I have the time & money (2030 maybe ??) but there are lots of people who have.....I'm sure someone will pop up soon....
 
 
I have seen the covertion kits but wonder about them. I know they work but do they last? the saito range of petrol are a lot more than £50 dearer than the glow equivalent and have heard the seals and rubbers on the glow motors wont stand up to petrol (I dont know if this is true or what other modifications saito has done to the engine to make it good for petrol)
 
the cost of the saito range at least omits any fuel cost savings but the advantages will still be less mess and potentially more reliable
 
the fs petrol in IMO would be more suited to scale (they sound better a 2 stroke petrol) High performance areobatic models use petrol for the performance. In scale models you are not always trying to get top performance from an engine and therefore can be set up to be as reliable as possible.
 
I just wondered if the advantages over glow make it worth while. I am sure a well set glow with on board glow circuit can be made very reliable. Glow seems to be going out of fashion.
 
I am currently saving up for a nice scale model (somthing like the new great planes waco) and when spending a lot of money on a model and set up I want to make sure I buy the best options available. when it come to the engine I will only be able to buy once and know anything I get will work (electric glow or petrol) but I want to satisfy myself first I am making the right choice
 
 
 
 
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"Making the right choice...." H'mmm thats a difficult one & probably depends on what you as a person/aeromodeller want & like to do.
 
For sure Electric will be the cleanest & simplest in operation....simply switch on & fly...but will probably be the most expensive to set up on a large model (I think that Waco is a pretty large aeroplane yes?)
 
Glow is simple tried & tested & a bit more powerful than petrol but will burn a lot of fuel in the 15-20cc range of sizes & cover your model in oil...
 
Petrol..probably a slightly more reliable idle than a glow but not much in it. Slightly less powerful than glow & will burn less (cheaper) fuel & not cover your model in oil (a few black specks but thats all). Unless you buy a Saito or similar you will probably have to do the conversion yourself.....which you might see as a hassle....
 
So thats probably the hard facts of the matter....is it enough to make a choice? Well again that depends on you.....I readily accept the advantages of electric & you certainly can't argue with the performance but I like fiddling with engines & I get satisfaction from starting & tuning the motor & getting good performance from a live fuel burning engine. In short I LIKE all the palarver that goes with a glow motor.....to me, an electric version lacks the soul & the drama of an IC powered model....but then I'm probably a bit weird...!
 
I understand your comments regarding longevity of a glow motor converted to petrol too...glow motors are designed for 18-20% oil have several plain bearings (conrod in particular) How long will these last on 4% oil? I don't know but you hear good reports about the petrol conversions & I suspect that if the conrods were failing regularly we would have heard about it by now...
 
Have I helped....? Probably not but what it comes down to is you....its your hobby & it depends what you like doing. There is no "right" or "wrong" choice....only Phil B's choice...
 
Enjoy....
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thanks Steve you comments do help. I have a bit of time to think about it anyway as it will take me a while to save up. Buying a second hand engine and a convertion kit to play about with before I buy a new model may be an idea.
 
electric I can rule out as i want a scale(ish) sound. there is another option of a muli cylinder glow (but I think cost rules this one out too)
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