It would be much easier to directly take the already rotary energy from the moving parts and couple that to a generator, but that would do good only on electric or hybrid cars to charge the batteries in it, and in fact many electric cars do that.

Once you've been driving for even a few minutes, the battery will already be topped up. There would be nothing to do with the meager power you collect. I really wish people would give up on these car wind turbines. The only viable use for a wind turbine would be to charge an electric car's battery while it's parked. But it would have to be very large. It would probably only be practical if you had it set up permanently at home, not a mobile one.

Personally I don't see the gain here, what is it actually that you are trying to achive?, or said different, what is the whole thought or bigger picture behind it? If it is to create some kind of 'green energy', then you would do better by investing the money otherwise spent on the adjustments made to the car in buying a new or second hand bicycle and leave your car at home once in a while...?!

Sorry, I was trying to make use of a useless idea, as you will note, I understand it produces a gain of power that is very negligible, I am making a vain attempt to justify the time spent by others on such endeavour, (and burning up a bit of time I have spare).

I suppose the over all aim would be to cut car emissions, possibly by a grand total of 0.003% or less, but hey, every little helps!

Sorry, I was trying to make use of a useless idea, as you will note, I understand it produces a gain of power that is very negligible, I am making a vain attempt to justify the time spent by others on such endeavour, (and burning up a bit of time I have spare).

I suppose the over all aim would be to cut car emissions, possibly by a grand total of 0.003% or less, but hey, every little helps!

Sorry, I was trying to make use of a useless idea, as you will note, I understand it produces a gain of power that is very negligible, I am making a vain attempt to justify the time spent by others on such endeavour, (and burning up a bit of time I have spare).

I suppose the over all aim would be to cut car emissions, possibly by a grand total of 0.003% or less, but hey, every little helps!

Someone in "Alice in Wonderland" claimed that anything said three times is true. Evidently the idea caught on.

Recovering energy like that is already being done with regenerative brakes. A possible advantage of a wind turbine would be that it could generate electricity when the car was parked. Sitting in a parking lot all day in Chicago could provide a worthwhile energy yield.