Air and E.T.'s

[SpeedThrills]

This is well known to most who race, but I thought I'd bring it up anyway.

I read a lot of posts about e.t. improvements after changing the combo.

As most do, only one modification at time can be evaluated.

Here's what I'd like to point out (to those who may not have considered it): That one change you make must be tested several times (different days) because of the difference temperature, humidity and barometric pressure can make. A weather station makes this easier, but you have to race a lot to become familiar with how to evaluate the info it gives.
This is mostly for small changes. Several small improvements make for a well sorted combo that runs "right".

My own personal experience comes from a Stock Eliminator car that varied roughly .25 of a second, just based on the weather.
I also bracket raced a completely stock '72 340 Demon that ran between 14.75 and 15.25 the one full season I raced it. I made zero changes to it. The weather ranged from cool, dry, high pressure spring time air to 95* plus temps, high humidity summer air.

-Just wanted to provide some food for thought.

 

[pettybludart]

I,ve noticed a change in my e.t with tire pressures in the cooler weather.This is why it,s always good to keep a log book of each pass while making changes.This way you can always swith back if you run slower.JMO:read2:

 

[03ramit1]

yeah I have seen huge changes. I used to race in el paso where the density altitude (da) would rane in the 4000-6500ft area. Now in phoenix it's 0-2500 and just driving from el paso to phx I dropped from a consistent 16.0 to 14.8 I have always said that it takes a good 4 to 5 trips to the track, and then you need to average the runs to get a good baseline. Make a change and do it all again. Otherwise you will not get a fair comparison. I haven't raced since june, (when my truck was totaled) but I can't wait to get out and hit it hard again once the duster is built

 

[68dodge]

I run at Pittsburgh raceway park. If the humidity is low, my car will run alot faster. I ran down at Mason Dixon dragway in Maryland with higher temp. and humidity and lost 2 tenths on my times. So your times are going to be different with temp. and humidity.

 

[70aarcuda]

keeping records of your run as to what the DA was at the time of the run will help in tracking changes...

a simple air temp...barometer and humidity guage which can be bought from radio shack or wherever...will allow you to do that...then there is software available that you can plug these numbers into that will give you the DA......or you can buy a 400-500 dollar weather station...

make sure you use the absolute barometer pressure...not the one given from the weather station as it is correct...