v tech engines in honda cars

many times you found that honda is using vtech engines in its car and now days also other manufactures are providing this types of engines in thier car such types of engines.

so wat is vtech technology??
it comes in picture in motor race when honda starts to participates in such events but that engines was very powerfull .but the main problem was that it waas not economicaly. so honda starts to develop the engine such waas economical with powerful .then vtech engines comes in real picture.

there r 4 types of vtech engine:dohc vtech, sohc vtech, vtech-e, 3 stage vtec