Quote:
Originally Posted by Arminius
Blind studies are not reasonable in this situation. In fact, if you only trust blind studies, all posts on this forum are useless to you.
|
Yours was one of the few experiments here that would be easy to blind since the modification was small and isn't visible from the driver's seat.
Quote:
Originally Posted by Arminius
I'm used to dealing with enclosed systems where air dynamics don't play much of a role in a system that is designed for larger volumes of are than are actually used, so I didn't exactly know what to expect in this situation. The results of this test, then, are in line with my experiences with enclosed systems involving waterlift.
|
I'm not saying it isn't possible - nobody can solve the air flow equations so there could be all sorts of surprises. It just doesn't seem likely to me that a small amount of air blown into the one to several cubic meter trailing low pressure region would do much.
I did think of another possibility. When the cabin is sealed the fan is pushing air into a closed space so the internal pressure of the car goes up. When you unplug the two back holes you reduce the cabin pressure by some amount, and the fan doesn't have to work as hard to move air into the cabin. So it draws less current, so the alternator is on less to provide that current, so the MPG goes up slightly compared to the "fan on, holes closed" case because the engine is loaded less. This may actually be a a gas saving technique (albeit a small one) via a mechanism that has nothing to do with the car's aerodynamics. If this hypothesis is correct plugging the back holes and slightly cracking a back window should give some FE improvement too. We've all seen the A/C versus windows open arguments, but I do not recall anybody measuring fan +/- windows open.