SuperMID M1, MPG Computer

[krousdb]

Originally Posted by SVOboy

Calibrate you speedometer and then check it out with a stop watch,

I am also very interested in this, need to buy a damn DMM so I can do your set up first though. Inaaccurate NJ pumping is killing me.

I have found that mile posts are very accurate over long distances. I have tested this in many states on many interstate highways and have always gotten very close results with the same car. I have tested the Prius on 100 mile stretches of the PA turnpike, OH turnpike, New York, Indy Turnpike and some state routes in the Carolinas. Sure, if you do a test for 10 miles you could be off because there is an obsticle where the marker post should be so they move it a few feet. But over 100 miles or even 50 miles, over many different roads, my Prius odo would show within +/- 0.2% of the mile posts. I just do it as a habit on long drives. Something to keep me from falling asleep.

Now the speedo thing might not be quite as accurate. First, don't necessarily assume that the speedo accuracy is equal to the odo accuracy. For digital speed readouts like prius, both use the same speed signal and display digitally so they should be the same. But with analog speedo/odo like my del sol, because there are two analog devices that use a common speed signal, you have some error that could occur. The needle could hang a little or be heavier from one car to the next. I have found that with the Outback and the del Sol, the speedo is lower than the odo, by about 1 MPH. Probably err to the low side for legal reasons.

I use the stopwatch method that you suggested for speedo calibration but it is much more difficult because you have to keep it on 60 and cruise ain't perfect. If you have hills or traffic, you are likely not to maintain 60 for very long. I have a 28 mile of flat state route in SC that I test speedos on. Perfectly flat and no traffic so cruise can give good results. It will be hard to test the del Sol down there. No cruise and it's hard to get the family of 4, a dog and vacation gear all in the del Sol.

The other method of speedo calibration is to drive by one of those speed signs that they place out every once in awhile to warn people to slow down. Problem with those is that they seem to be off by quite a bit.


I'm rambling now.....