April Tech 101 Article

By:Fran Pepi

As bracket racers, we all know the importance of accurate weather information in order to predict the performance of our racecars. Your basic readings are temperature, relative humidity, and barometric pressure. I started out years ago with an inexpensive home type unit that’s made to hang on the wall. It may not have been dead on accurate, but it showed you trends as far as the movement of the readings. After numerous passes, along with accurate log book records, you could fairly accurately predict the cars performance. I upgraded to a $25 digital temperature and humidity unit from Radio Shack years ago but still used the cheap barometer up until last season. Again, it served me well over the years but there were times that the weather would throw you a curve. These were the runs where you’d scratch your head wondering, where the heck did that come from! For years I wanted to get a quality weather station but it was never in the budget. The weather station/et predictors were more than I wanted to spend and like I said, I did a fairly good job predicting my cars performance. I just wanted something that was more accurate and would give me a density altitude calculation. Density altitude is a very useful piece of information which takes into account temperature, humidity, barometric pressure, altitude and dew point. It is a mathematical calculation that modifies your actual altitude to what it would be like with certain weather variables. For example, let’s say your track located at 500 feet above sea level. You could have middle of summer high temperatures and high humidity which would make it seem like air at 3000 feet(less dense) above sea level. That is what the engine sees and performance will suffer. In bracket racing your adjustment for that is your shoe polish(dial-in). For other forms of racing that depend on the most horsepower, it may be a jet change, timing adjustment, etc. to tune for more power. This is also useful to pilots for adjusting engine power, runway length for take-off and so on. Air that is less dense causes a decrease in engine power and that also means an aircrafts wing will generate less lift.

After some research, my choice for a meter is the Kestrel 4000 Weather Tracker which is manufactured by Nielsen-Kellerman (nkhome.com). They manufacture equipment for sports, construction industries, the military, pilots, racing, etc. Check out their website and also their Knowledge Center for a wide variety of equipment and tech information. The 4000 will read wind speed, temperature, wind chill, humidity, heat index, dew point, wet bulb, barometric pressure, altitude and density altitude. It will store data and it can be uploaded to a PC with an available serial port interface. You can check out the too numerous to list features on their website. I have one on order and once I receive it and put it to use I will give an evaluation of it in an upcoming segment of Tech 101. I would like to thank Christy Munding(Business Development Manager) and Ben Churchill(Tech Support Manager) at Nielsen Kellerman for their prompt and courteous response to all my questions. Questions and comments are welcome and can be sent to me at FP442@aol.com

By: Fran Pepi