Wednesday, June 24, 2009
Results
I have 2 metrics that I will be using throughout my project, the first is gas mileage. Since I use this car to commute to and from work for a round trip of 70 miles a day, mostly highway, I should be able to get repeatable results as long as control my speed. The benchmark from when i first got the car has been a repeatable 28mpg every week and now I am averaging 30mpg. The other metric that I will use throughout this project is a rolling speed down a steep hill on my way home from work. There is a hill about a mile long that I usually enter around 65 to 70mph, after about 30 seconds the car has slowed to a coasting speed and will stay at that speed for the rest of the hill. I've also entered the hill with around 55mph and the car has speed up to the coasting speed. When I bought the car I would coast around 58mph with the top down and 60mph with the top up, after my modifications I have been coasting with the top down at 60 to 63mph depending on the wind and with the top up around 63 to 65mph.
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3 comments:
Have you been monitoring these speeds vs. time of year (thus temp) and relative humidity (also a sub-function of the time of year)? These will have an effect. Similarly, the aero would likely be overcome by slight variations in tire pressure. Even the tire wear that occurs over the course of a year would influence your numbers...especially if you're using the car's speedo to measure.
I think that the tire pressure will have an effect on the results but I try to keep my tire pressures at the same PSI. The weather has been rather mild since I've started testing so hopefully the environment variables haven't been too volatile. I think one of the biggest factors will be if there is a head wind or a tail wind for each test. Its nice that I get to test it practically every day so I hope that will flush out some variables as the number of data points go up. I think that it would take a a while between tests for the tire wear to show up in the results (ie difference between January and August compared to Monday to Friday)
Ok, I mainly didn't know how long you'd been measuring. I agree that an increase in the number of data points will certainly help, but on the flip-side, the longer you're measuring the more things like varying tire pressure, wear and environmentals will show up.
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