See also: http://ecomodder.com/forum/showthrea...olla-2390.html
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As promised, here's the low down on the A-B-A test that I did using my brother's 2005 Pontiac Montana minivan: long wheelbase version, 3.5L V6, automatic.
As I mentioned in the
van Kammback thread, conditions were ideal. Zero wind, and no traffic on my favourite testing route, and a cruise control functioning perfectly (unlike the one in my Firefly, which quit while
testing the Kammback).
Here's what I did:
1) OEM roof racks were removed, holes covered with tape.
2) Vehicle was driven for approximately 25 minutes / 20 km in sub/urban and rural highway conditions to bring the vehicle up to operating temperature. Ambient conditions:
October 5, 2008 - 18:00
10 C / 50 F
71 % relative humidity
102.5 kpa pressure
0 wind
Cruise control was set once for the entire A-B-A series, at 55 mph / 88.5 km/h. Cancelled with the brake at the end of each run and "resumed" for subsequent passes between the same markers each time. Fuel consumption taken from a ScanGauge II, reset and read at the same markers each run.
3) 4 bi-directional "A" runs were done, averaging
33.65 mpg (US).
4) Airtabs were installed on the top & sides of the van (following mounting instructions on their web site, except they were taped on their leading & trailing edges, rather than peeling off the adhesive backing and sticking them on).
5) 3 bi-directional "B" runs were done, averaging
33.8 mpg (US)
6) Airtabs were removed, and 2 more 2-way "A" runs were completed, averaging
33.92 mpg (US).
Average of
all "A" runs:
33.72 mpg (US)
Standard deviation of all the "A" runs: 0.36 mpg
Raw data:
Code:
West East AVG
A 33.8 34 33.9
A 32.8 33.4 33.1
A 33.6 33.9 33.75
A 33.7 34 33.85
B 33.3 33.8 33.55
B 33.5 34.2 33.85
B 33.5 34.4 33.95
A 33.6 34.2 33.9
A 33.9 34 33.95
Pics:
Below are the OEM roof racks. I think those are aftermarket cross bars though:
Air tabs shown - placement only. For the actual test, they were taped across the full leading edge, and on the trailing tip, so they sat flush against the sheet metal:
Side placement. I was advised by the distributor that where the airtabs were set on an angle (rather than perfectly vertically), to increase the spacing between them slightly. So the ones behind the side window area aren't the usual "4 inches on center" layout.
