"Most of the wood gas automotive systems used during World War II used charcoal, instead of raw wood, so that they could skip the pyrolytic phase and minimize the size of the generator. Doing it all in one generator requires a larger, more sophisticated unit, and if you have room, then it's the way to go, and go farther, since you get more energy out of a pound of wood if you burn both the charcoal and the pyrolytic gases."
Check out the Wild Stoves Wild Woodgas Stove at Cotswold Outdoor. A neat and simple idea, brilliantly executed: the ingenious Woodgas stove efficiently and cleanly burns natural fuel, cleverly channeling excess.
Weekend Project: Make the Ultimate DIY Wood Burning Camp Stove