Dumb Question

[Sacto John]

Why do 2 strokes need oil mixed into the fuel? How does this lube the motor? How does the oil delivery systems differ from DI motors, EFI motors and Carb motors. Had a friend ask me and I did not konw the answer so I though I would ask.

[jgwufgator]

Read this:
http://science.howstuffworks.com/two-stroke.htm

[Sacto John]

Thanks, that helped. I am still courious in how a DI motor, like an E-Tec or FITCH, is more oil efficent and produces less polluntants.

[25xs]

John posted: <<I am still courious in how a DI motor, like an E-Tec or FITCH, is more oil efficent and produces less polluntants. >>

Because when you mix the oil with gas either in your tank or a oil injection pump such as the VRO/OMS, you're using a "shotgun approach" by sending oil everywhere inside the crankcase instead of just where it's needed. When the gas droplets with oil dissolved in them evaporate and head to the combustion chamber via the intake ports , the oil precipitates out and coats the inside of the crankcase and is slung everywhere. Not just on the needle bearings and surfaces where it's needed, the oil is just slung everywhere and distributed by the turbulent airflow through the crankcase before it's either blown into the intake passages to the combustion chamber or else pulled into a recirculation line and back in through a carburetor.

The DI motors use a "rifle approach" (dedicated oil pump) and put the oil ONLY where it's needed and don't mix the oil with the gasoline at all. They inject oil into the crankcase at locations that put the oil right on the rod journals and needle bearings. The oil is still pulled through the crankcase by turbulent air and ends up in the combustion chamber or recirculated back to the intake manifold, but much less is needed when you put it only where required instead of shotgunning it everywhere.

Yeah this is oversimplified but it's true and might help you see the difference.

Tom

[Bassmeister]

There is a small amount going into the gas to keep the injectors clean and any excess is then sent back to the tank also.