ET Prediction Calculations

Rusty2211 · 09-10-2009, 09:53 AM

Does anyone out there have a spreadsheet or the formulas for determining ET based on changing weather conditionsf or a gas powered car? My Sharp programmable calculator bit the dust. I simply entered Temp, Humidity and Barometric Pressure into it and it gave me a factor that I could use to compare to old runs and factors to determine my new ET. It worked great. I know this stuff is not rocket surgery, but I can’t find any resources online.
Thanks Rusty

Redlight · 09-10-2009, 10:20 AM

These should help: http://www.wallaceracing.com/Calculators.htm

Alan Roehrich · 09-10-2009, 01:51 PM

Google "Max Race Software". Larry has a nice ET prediction program, it is very specific on all inputs and it does a nice job.

www.maxracesoftware.com

Larry may have taken his free version down. If you cannot find it, you might try emailing him.

Michael Pliska · 09-10-2009, 05:29 PM

Quote:

Originally Posted by Redlight

These should help: http://www.wallaceracing.com/Calculators.htm

http://www.wallaceracing.com/convert-et-to-msa.php

Maybe I'm doing it wrong, but I input 1st run of 9.40 @ 141 at 300' elevation, 70°, 45%, and a 2nd run of 2500' elevation, 80°, 45%, and it predicted I would run 9.29 @ 142.72!!!

I created a spreadsheet to do Density Altitude calculations (I'm too cheap to buy a real weather station that does it for me). It is a combination of stuff I found in textbooks and the internet, with an additional factor added to make it match NHRA's value (when they post Density Altitude on their racing results pages). Here is the cell formula:
=(44.3308-11.1802*((D3*3386.389/((((D1-32)*5/9)+273.15)/(1-0.378*((6.1078*10^((7.5*((D1-32)*5/9))/(237.3+((D1-32)*5/9))))*(D2/100)/(D3*33.8693)))))^(0.234969)))*3280.8333+(550+((44. 3308-11.1802*((D3*3386.389/((((D1-32)*5/9)+273.15)/(1-0.378*((6.1078*10^((7.5*((D1-32)*5/9))/(237.3+((D1-32)*5/9))))*(D2/100)/(D3*33.8693)))))^(0.234969)))*17))

D1 = temp °F, D2 = humidity as whole #, D3 = barometric pressure in-hg

It's not perfect, but it comes pretty close to NHRA's and the other commercial weather stations. I use it with a cheapo electronic weather station that has temp, humidity and pressure.

Regards,
Michael Pliska

09-10-2009, 09:53 AM	#1
Rusty2211 Member Join Date: Dec 2004 Location: Georgia Posts: 118 Likes: 1 Liked 0 Times in 0 Posts	ET Prediction Calculations Does anyone out there have a spreadsheet or the formulas for determining ET based on changing weather conditionsf or a gas powered car? My Sharp programmable calculator bit the dust. I simply entered Temp, Humidity and Barometric Pressure into it and it gave me a factor that I could use to compare to old runs and factors to determine my new ET. It worked great. I know this stuff is not rocket surgery, but I can’t find any resources online. Thanks Rusty

09-10-2009, 10:20 AM	#2
Redlight Junior Member Join Date: Aug 2009 Posts: 23 Likes: 0 Liked 0 Times in 0 Posts	Re: ET Prediction Calculations These should help: http://www.wallaceracing.com/Calculators.htm

09-10-2009, 01:51 PM	#3
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,105 Likes: 1,561 Liked 1,789 Times in 408 Posts	Re: ET Prediction Calculations Google "Max Race Software". Larry has a nice ET prediction program, it is very specific on all inputs and it does a nice job. www.maxracesoftware.com Larry may have taken his free version down. If you cannot find it, you might try emailing him. __________________ Alan Roehrich 212A G/S Last edited by Alan Roehrich; 09-10-2009 at 01:57 PM.