"E Brown" > wrote
> "sgfan3" > wrote:
>
>>Funny! But seriously, why do they even exist? Do they actually help the
>>air flow over the top? I would think that the smoother lines (without the
>>spoiler) would flow the best.
>>
> A spoiler directs airflow, not improves it - it's chief use at the
> rear of a car is to increase downforce; to make the air push down on
> the car.

Except the OP is talking about a *ROOF* sunroof deflector, which
is an entirely different subject than you are talking about.

FloydR