4 stroke petrol engine but using 2 stroke fuel ???

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4 stroke petrol engine but using 2 stroke fuel ???

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10 April 2022 at 22:54 #100096
Former Member
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@formermember67585
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10 April 2022 at 22:54 #8249
Former Member
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@formermember67585
wrong fuel in motor.
10 April 2022 at 23:31 #100100
Chris Fellows
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@chrisfellows72943
I'm guessing that it doesn't have a lubrication system like a full size motor i.e. an oil tank or sump and an oil pump and so needs the oil in the mix for lubrication?
11 April 2022 at 00:11 #100101
Former Member
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@formermember67585
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11 April 2022 at 00:34 #100102
Former Member
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@formermember67585
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12 April 2022 at 11:38 #100122
Richard Simpson
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@richardsimpson88330
Obviously the fuel is the same for both two stroke and four stroke with the only difference being that you add the lube oil to the two stroke fuel. The odd thing to me is that the oil was added to the fuel to lubricate the bearings in the crankcase as the fuel flowed through there to get to the inlet ports in the cylinder. In a four stroke engine the fuel goes directly into the cylinder via the inlet valve.

This begs the question to me, how are the big end and main crankshaft bearings lubricated?

No matter how much you think you have seen it all there is always an engine out there that doesn't do things according to the norm!

Edited By Richard Simpson on 12/04/2022 11:40:06
12 April 2022 at 12:02 #100123
Ray Wood 3
Participant
@raywood3
Hi All,

I have several aeroplane 4 strokes, they run on fuel & oil mixture and only have 2 exhaust valves in the head, as Chris said a while back they don't have oil sumps so they need the oil coming up from the crankcase to lubricate the bore. Spark ignition has become popular to convert glo motors to petrol because it's cheaper than glo fuel for the bigger engines.

Regards Ray
12 April 2022 at 13:27 #100124
Richard Simpson
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@richardsimpson88330
Interesting thanks Ray.
13 April 2022 at 22:10 #100137
Chris Fellows
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@chrisfellows72943
Posted by phill downes on 10/04/2022 22:54:14:

I just look at the new model boats mag site and see something i think is a bit weird…. they have a page about a new 38cc 4 stroke motor for model planes… when reading the topic and about the new motor i see a bit where it says they are using fuel at a 25 to 1 ratio ? can anyone explain why they would be using a 25 to 1 petrol to oil fuel mix that would be 2 stroke mix in a 4 stroke motor… i have never heard of anyone doing this before…… any idea on this.. the motor is clearly a 4 stroke as you can even see the valves for it and the piston etc…

Meant to ask Phil. Where did you see this?

Chris
14 April 2022 at 10:15 #100140
ashley needham
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@ashleyneedham69188
Engines that small cannot have an adequate pump and oil distribution system, with tin tiny oil ways and so on or at least, not cheaply) Then there’s the sump arrangement…dry or a tank, gravity to think about, capacity of the oil reservoir and oil cooling.

Having oil in the fuel is so much easier and adequate for the task, as it works for two stroke motors of similar size.

Ashley
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