Quote:
Originally Posted by Longshot270
If recording more increases your % error then you shouldn't even be watching it to begin with. Your chance of error goes down when the number of samples goes up.
Here is a quick example of why short term averages are bad. For easy math (and since I'm not positive on the official rates other than the data stream rate) we'll say the programmer takes 5 readings per second.
Lets say you have two different calculations going. One set of calculations has a small number of readings at 1000 readings and the other has a large number of readings at 10000 readings. If the current average is 16 mpg for both then it is easy to see how a single stretch of road could impact the mathematical formula.
You climb up a hill with an IECON reading of 5mpg for the 10 seconds it takes to climb up that hill. Then you slowly roll down the other side of the hill with zero throttle input (maxing out the IECON at 40mpg) dragging on the brakes (to not speed and ram the little old lady ahead of you) for 15 seconds. Your average in this section of road is 26 mpg according to the programmer.
Factor that into the "small" calculation and once you are back on the road your average is 17.1. The large equation comes out to 16.1. If you then compare to the "full" amount of 100,000 readings, you end up with 16.0, or no noticeable change. Keep in mind, this is the impact of only 25 seconds of drive time, now consider what happens when you are cruising through traffic or hilly areas where you are switching between the gas and brake pedals as well as changing speed often. If you were able to freely roll down the hill to shorten the recording time, the average would not be thrown off as much. Unfortunately the computer cannot account for elevation changes, lack of throttle input, resistance from wind and tires, etc. Until then the average will not be completely accurate except under ideal conditions.
|
Your math makes perfect sense to me, and unless it was recording wrong on something, the longer it's in the more accurate it is, but I still dont know why my average mpg's change so much. I am driving back tomorrow and Ill report on how they do, but I expect them to drop to about 12 or less going up parley's canyon (pretty big canyon here), then raise to about 15-17 as I hit the park city exit, then lower to 14 by the time I am to Evanston... and this is without ever resetting the Gryphon. the only time I have ever seen it reset is when I unplug it when going to the dealer to get free oil changes. If anyone's Average mpg's are more steady than mine then please let me know, and even though I got an oil change a little more than a week ago (aka not much time calculating) I have seen this same behavior every time I drive my truck ever since I got the Gryphon, and it's been both trucks too... maybe I have a bad hardware something that doesn't record as many points of data...
Oh well though, I have had mine for almost a year in this truck, and it was almost a year in my other truck too, and I am not planning on changing because of a miscalculation in my percieved mileage... I know I suck at getting good mileage, but I didnt get a truck to get mpg's, I got it because it's useful, and safe, and also fun
... oh and BTW it hasn't helped get any girls either... maybe that will change in texas...
