One day, while I was surfing at 3D Cafe , I saw that Peter Watje created a new plug-in, Particle Combustion. In this section, we'll create a spray like the one you can see in fig. Now, let's have a look at the parameters you used. As you probably know, Viewport and Render Count deternime the number of particles in the respective views. Drop Size is the size the particles have.
Variation determines the variation of the direction of the particles.
Here, I set it to 5 but with you want to increase the transversal amplitude of the spray, just increase it. Speed is the velocity the particles will emit with. Start indicates the frame from which the particles begin to emit. Life indicates the time until the particles disappear. Ok, now we'll assign a material to this spray.