What are the differences between otto cycle and diesel cycle?

Mister Rudolph Diesel was aware of the gasoline engine ([http://en.wikipedia.org/wiki/Otto_cycle Otto cycle]) problems and wanted to improve it. The gasoline engine inherently has problems with efficiency and/or fuel. In order to improve the efficiency one must increase the compression ratio of an internal-combustion engine (see the bonus section at bottom of this article). However, in the gasoline engine there is a limit - the gasoline-air mixture will self ignite once the compression gets too high (because every compression drives temperature increase). So, either you can have a low-efficient, low-compression engine that uses a cheap fuel, or you can have a high-efficient, high-compression engine that uses expensive, high-refined fuel that wont self-ignite even at high compression levels (a 120 octane gasoline?). In [http://en.wikipedia.org/wiki/Diesel_engine diesel engine] this problem is solved. The diesel engine can use much higher compression levels than the gasoline engine reaching higher efficiency. In addition, the diesel engine can use fuel that is not nearly as refined as the high-octane gasoline fuel (thus cheaper). To make this possible, Rudolph changed the Otto cycle and created the diesel cycle. The difference is that during compression phase, no fuel is present in the cylinder and thus no self-ignition can happen. The fuel is only injected at the moment the ignition is wanted - when injected into the hot pressurized air the diesel fuel self-ignites immediately (the diesel-air mixture, as we said already, is happy to ignite even at relatively low temperatures).