Thread: a question from my auto exam

cheaper to make
higher power to weight ratio
No requirement to have internal lubrication system
less moving parts

Originally Posted by schmierer LR at singleton

once agaon good answers i sed they are cheaper to repair and that they have more power for the size of the engine

In racing circles, the 4 strokes are now able to produce more power than a 2 stroke for a given capacity. The problem with a 2-stroke is that even with expansion chambers they are still not an efficient motor. The other limitation is that 2-strokes is that they cant really make peak power happen beyond about 11,000 rpm, though they can make it linger well beyond that rather than falling off. 4-strokes they can make pull for as long as things remain in synch. I think F1 are hitting around 18,000rpm and I'm not sure what the bikes are doing these days.

2 stroke benefit - no o/h valves, simple power valve set up, no complicated head, no timing chain.

not always...

Ive seen 2 strokes with timing chains and over head valves.

Yep. diesel 2 strokes.

The petrol 2 stroke with rotary/disc valves can also have a timing belt when the intake is aligned with the gap in the crankshaft rather than the normal side entry.

Mazda rotarys are effectively a two stroke and had their capacity doubled (on paper) after their first year of racing to make the other cars competitive. Gricey cleaned up that year. You also have two stroke diesels like the twin knocker. You can even have 1 stroke steam engines and the Stirling engine

Deano

Originally Posted by DeanoH

You can even have 1 stroke steam engines

Deano

would that be a steam cannon?

Originally Posted by CraigE

2 stroke benefit - no o/h valves, simple power valve set up, no complicated head, no timing chain.

Not necessarily - some two stroke diesels have overhead valves. Some two stroke diesels have no head cylinder head; e.g. Junkers style engines. Simplicity is not necessarily a feature of two strokes.

John