Hi Guys,
Can you please help me understand weather and using it to help predict e.t.? I do not currently have a weatherstation and I was wanting to learn how to do it the old school way. I can get the basic info from track and such, but I imagine you can somewhat calculate an estimate to a certain extent can't you? I would just like to have an understanding of a shomewhat educated guess you know? Thanks for your help, Mike.

For good ET prediction, you will need to know exactly how much oxygen is available to burn the fuel. Tempurature, humidity (takes up room,less oxygen) and barometric pressure will all affect this. The other part of the equation is how close is your jetting? Lean, and it will not pick up ET as much for better air. Conversely, rich will alter your ET more. So what you need to do is come up with the DA (density altitude) which is computed using all three weather stats. Then start recording your ETs at different DAs. You will see a pattern start to form. A 1,000 ft DA change may cause your car to go .05 slower or faster, or more, or less. Once you have enough data, you can then predict ET. Be sure and record wind direction and speed as well, and 60 ft variance. MPH at the 1/8th and 1/4 is a very good indicater given the wind speed/direction is the same, because 60 ft times have little effect. You can use mph to give you a better prediction if the car spun, by looking at previous runs and the ET Vs mph.

You need four weather instruments to record the actual weather, air temp, humidty, barometer pressure and a sensitive(adjustable for barometric pressure)altimeter. You might be better off buying one of the Kestrel handheld weather instruments as it has all of those except a sensitive altimeter, it will give you a actual B.P. and a density altitude Do you have access to any avaition training books about density altitude, maybe there's some free information on the net I'm a instrument rated commercial pilot and air density is real important when flying in the mountains like you live in The actaul 02 content of the atomsphere(around 21 %) remains the same from sea level to above 25000 ft, but the density of the air around us does not so you end up having to suck in a lot more air to get the same amount of 02 the higher you climb. The 02 molicules are spread a lot further apart at 5000 FT above sea level than they are at sea level, add heat and humidity to the mix and it only gets worst

Don't miss out the obvious, a 20mph head wind will slow us down more than .2 and 4 - 5 mph in the 1/4 compared to a 20 mph tail wind.

When you get it figured out please share the info as some of us still cant figure it out

Well, so far I have figured out that after I unload the car the first check I do is look at the dresses to see if they are blowing around (head wind, tail wind), I check my Dads forehead, beads of sweat indicate watergrains in air. ( relative humidity). That's as far as I have gotten.

I don't have a weather station ether. We do get 3 time runs before eliminations start, so I do have a trend to look at. We also only have 15 minutes between rounds, which in this case, can be a good thing. I usually base my dial on the trend and my last pass. I'm usually within .03 and several times this year I was dead on.