Randy's right. They made a lot of these and fitted them to other brands of cars
during WWII and they were called "producer gas" rigs. This is different from the
"producer gas" made in the coal/coke industry which is largely carbon monoxide and
hydrogen with some nitrogen added in (from the air used to propel the water
through the coal/coke).
Like Randy says, the gas here is the destructive distillation product of the wood and contains many different hydrocarbon compounds. It is a serviceable fuel
but NOT a high-performance fuel.
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George Downs, Bartlesville, Heart of the USA!