quote:
Originally posted by MolaKule:
Bob,
When discussed the 2-stroke, Were you referring to the electromotive 2-cycle with the silver
bearings?
GMC/Detroit Diesel used to produce a lot of small and medium sized 2-stroke diesel engines. The 6-71 was probably the best know--inline six and 71 cubic inches per cylinder. They had 8V-71, 12V-71, 4-71, 3-71, 2-71 (used on the reefer machinery on reefer railroad cars). They also had the -53 series engines and -92 series, probably others. I remember getting gas in a truck stop in Nevada years ago, and a guy went by in a pickup truck that sure sounded like it had a 4-53 in it.
Now Detroit Diesel is owned by Daimler-Chysler, includes the fine line of German MTU engines, and also some engines produced in Italy and Brazil. No more two strokers.
The two stroke uniflow power cycle was:
--Power: Piston near top-dead-center, injector sprays in fuel, piston is forced down due to the fuel comustion.
--Exhaust: Piston still moving down, exhaust valve(s) in head opens.
--Scavenge: Piston passes ports in the cylinder side, pressurized air flows in and blows exhaust out the exhaust valve.
--Intake: Exhaust valve closed, blower pressurizes cylinder with fresh air charge. Piston passes bottom-dead-center.
--Compression: Piston closes off intake ports as it moves upward.
Power: ditto above. All this happened on one revolution.
Two-stroke engines must have some sort of an air pump. Jimmies all had a supercharger, and some also had a turbocharger. Large 2-stroke engines have turbochargers and electric blowers to supply the air charge for starting and low load. Very small 2-strokers (outboards, etc.) use the bottom of the piston as an air pump.
Ken