Hitch Bike Rack's Effect on Vehicle Efficiency

[Seano]

Ok - so not exactly a study. All I could pull was ABRP data: it does not have driving temperature, but same car, same trip, same tires, same (very similar) tire pressure, very similar starting temps. I **think** trip 2 was colder driving temps. Same passengers, very similar items inside car.

1. Trip 1 Hitch Cover on: 253 mi... 100% > 70%; 312 Wh/mi first 124 miles, 437 Wh/mi last 129 mi
2. Trip 2 No Hitch Cover: 254 mi... 100% > 75%; 406 Wh/mi

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[BTOR]

Ok - so not exactly a study. All I could pull was ABRP data: it does not have driving temperature, but same car, same trip, same tires, same (very similar) tire pressure, very similar starting temps. I **think** trip 2 was colder driving temps. Same passengers, very similar items inside car.

1. Trip 1 Hitch Cover on: 253 mi... 100% > 70%; 312 Wh/mi first 124 miles, 437 Wh/mi last 129 mi
2. Trip 2 No Hitch Cover: 254 mi... 100% > 75%; 406 Wh/mi

This is really interesting. Thank you for posting.

First, do you know what may have caused your jump in kW/mi for the second half of your Trip 2? This skews the data a bit. It is definitely an outlier but doesn’t throw the theory out the window completely.

Comparing Trip 1 and your 1st 124 miles with cover in place vs. Trip 2 without cover, there is a significant difference: 3.2 miles/kWh w/ cover vs 2.5 miles/kWh w/out cover. That is a 28% difference which is significant. However, your efficiency dropped significantly the 2nd half of your Trip 1. If you average both halves of Trip 1, you get 2.7 miles/kWh. Which is still an 8% improvement over your Trip 2.

So it stands to reason that the cover plays a major role. I would suggest performing several more trials to get a few more data points to build confidence. However, this delta in efficiency is right in line with what has been reported empirically as well as the lab measurements from the technical paper.

 

[Seano]

Oh sorry... yes: why the diff between first and second 1/2 of trip... Look at the Elevation change

And here it is without stopping (good for scale):

 

[BTOR]

Oh sorry... yes: why the diff between first and second 1/2 of trip... Look at the Elevation change

And here it is without stopping (good for scale):

Yep, that explains it…….!

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