2 stroke petrol engine?

Question

Why is oil added to petrol in two stroke engines.
Can this be adopted for 4 stroke engines
is it possible to provide an oil pan to 2-stroke engine to avoid mixing of oil with petrol

Answer 1

Small two-stroke engines use their crankcases as a kind of pump to push in the intake and push out the exhaust. The intake air (with fuel and oil) is drawn into the crankcase by the upward motion of a piston. Then, a downward motion pushes the air, fuel, and oil into the cylinder (also helping push out the last of the exhaust). Since the underside of the pistons and the connecting rods and the crankshaft and all the bearings are in contact with the air and fuel, you can't have a four-stroke type of sump and lube system. All that oil would mix with the intake air and it would be a big, smoky mess. Because of this, the two stroke engine has to have a little oil mixed into the fuel to lubricate the rolling element bearings and the pistons.

Bigger two stroke engines sometimes use a supercharger to push the air into the cylinders. They don't need oil in the fuel, and they can have oil pans and a pressurized oil system just like a four-stroke. Detroit Diesel built many, many big two stroke diesels like this until about ten years ago. Popular in trucks, boats, and busses.

It would be entirely possible to design a four stroke engine to have no oil pan and use oil mixed in the fuel. The fuel and oil mixture would simply have to get around all the moving parts, all the bearings would have to be rolling element bearings instead of journal bearings, and the camshaft and valves would have to be designed to have appropriate loading. The engine would be more expensive to build, noisier, create more pollution from all the oil being burned, probably less reliable (journal bearings are more reliable than rolling element bearings), and perform more poorly (because the air would be hot from going through all the moving parts). But it is possible.

Answer 2

First part = No oil source is used in a 2-cycle engine because of the design of the open bottom end and chambers. Oil is added to the fuel to provide lubrication to the moving parts such as piston, and crank. There are few moving parts and that is why they are very strong engines.

Next part = I am afraid not. The 4 cycle engine cannot adopt this method because of the number of moving parts and the closed design of the same moving parts. Much of the engine would go without lubrication and seize quickly.

Last part = It is possible but it would be a futile effort. The expense involved would be great as you would need to incorporate what is referred to as a dry sump design.

Bottom line... don't bother - they are designed well the way they are. If you really want to get into some crazy stuff... look into rotary engines.

Answer 3

It is added because they dont have a lubricating system like that in a 4 stroke engine. They don't have complicated moving parts like the 4 stroke engine does. It is added to act as lubricant to minimize friction and heat at the pistons. No need for oil pan. The make up of the two contrasting engines are entirely different in their systems and the work they do.

Answer 4

It is possible to use an oil system similar to a 4 stroke engine in a two stroke. The reason for the added oil is that the heat buildup in a two stroke is twice that of a 4 stroke because it combusts every two revolutions instead of every four like in a 4 stroke so twice the heat buildup.

Answer 5

two stroke gasoline engines dont have a seprate place to put there oil but a four stoke does if the gas your wanting to use alreddy has oil in it go ahead and use it i did with my lawnmover on accdent and nothing happend.

Answer 6

no and no