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Old 04-04-2009, 01:42 AM   #14 (permalink)
Allch Chcar
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Join Date: Jan 2008
Location: North Coast, California
Posts: 429

Cordelia - '15 Mazda Mazda3 i Sport
90 day: 37.83 mpg (US)
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Quote:
Originally Posted by RobertSmalls View Post
A very interesting problem. I suspect that a wind-powered intake *ought* to be more efficient than an electric one, especially since you have a port for air to exit at the rear of the cabin. Since your alternator and blower motor are less efficient than your transmission, driveline, and tires, the latter should take less energy than the former.
Alternators are pretty efficient, the belt is already dragging so the extra drag to power the fans is relatively small.

Quote:
Originally Posted by MetroMPG View Post
Interesting - I would have predicted you'd have slightly higher pressure and better flow through your windshield-base vents after lowering the stagnation point with your new front bumper (more airflow going up & over the hood.)

The hood/windshield angle hasn't changed has it? Could it be related to the windshield wiper deflector? Do they cover the vent inlets at all?
It sounds like his air vents are the new "Vaccuum."

If you're providing a smoother path for the high pressure air, which is the goal of moving your air vent intake to a high pressure zone, then the drag should be reduced and the air pressure will be closer to ambient. With your air vent intake pulling air slower, you're probably sitting in a higher pressure zone than your intake. Changing the air vent intake should increase your airflow and reduce drag. Maintaining good airflow in your cab can reduce your drag and increase your comfort. If you're still not getting air flow use your vent fans to pull air in then use fans to increase the air pressure behind your tail. They'll pay for themselves if you use them to recycle air pressure and the better airflow, to a point of course, the better your ride will be.
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