Explain the bottom of my slip

[Racecraft]

Well after listening to the too hot, too humid blah blah blah, can someone enlighten me as to what 'ideal' values the following would be?

For example last night @ 10pm the following:-
21Deg, 87% Humidity, 1008mB,1522RA, (TT)31Deg

THese values are printed on the bottom of every slip @ Willowbank

Now i can understand cooler atmo weather is good, but what effect do the other values have on your ET..

I am also curious as without some sort of understanding of how to standardise these values I am finding it hard to know if I am getting faster, slower or exactly the same performace from my $hitter.. For me I went 2 weeks apart with a few tweaks but the car went no faster but had an extra 1mph ( a pitance I know but everything counts :P)

So you can see my issue, are my tweaks working, just combating the different track conditions or did the car actually go slower than the week before?

[xr8ute]

I believe the RA (relative altitude) is the most significant figure, with respect to comparing timeslips with different conditions.

Some info on relative alititude (also known as Density Altitude..?) and timeslip correction here, http://www.quarterjr.com/members/weathertech2.htm

[Quadcams]

Originally Posted by Racecraft

Well after listening to the too hot, too humid blah blah blah, can someone enlighten me as to what 'ideal' values the following would be?

For example last night @ 10pm the following:-
21Deg, 87% Humidity, 1008mB,1522RA, (TT)31Deg

THese values are printed on the bottom of every slip @ Willowbank

Now i can understand cooler atmo weather is good, but what effect do the other values have on your ET..

I am also curious as without some sort of understanding of how to standardise these values I am finding it hard to know if I am getting faster, slower or exactly the same performace from my $hitter.. For me I went 2 weeks apart with a few tweaks but the car went no faster but had an extra 1mph ( a pitance I know but everything counts :P)

So you can see my issue, are my tweaks working, just combating the different track conditions or did the car actually go slower than the week before?

RA is what you should be looking at as its a combination of air temp/humidity/barometric pressure. Anything under 1000ftRA is starting to become good air and roughly every 1000ft drop in Ra you should gain about 1.5tenths and about 3mph (roughly). RA (relative altitude) is a mesurement of the quality of the air, some cases you can get a negative Ra reading in some places, obviously mostly ih the winter months

So when racing you need to take into consideration your 60ft to ET, then take into acount the RA and you can get a good idea how your car is performing. This time of the year is not a good time as the humidity is through the roof and also air temp is rather hight which will affect the RA considerably but is some cases the humidity can be high but still the Ra is around the say 800ft (not to bad air) so if the humidity is high doesnt necessarily mean the air is bad, eg I have had times when the humidity is at 100% but the Ra was around 670ft quiet good air, so humidity/air temp/barometric pressure in different combinations can give very different Ra results, but air temp is the main factor that will affect the RA.

Have a play with this density altitude calulator ( same as relative altitude)
and you will see the affect different conditions will affect air quality, but rember the barometric pressure is in mercury reading and altitude is height above sea level where the reading is taken.

Density altitude calculator

[FLUB378]

The higher the humidity, the more water there is in the air. Water doesn't burn so that means that the air/fuel mixture in your cylinder has a higher percentage of water. More water means less fuel and/or air, therefore less bang inside the cylinder. The lower the humidity, the better. Petrol cars are affected more by high humidity than a methanol car. The barometric pressure is the air pressure naturally, therefore that higher the barometric pressure, the higher pressure the air is getting pushed into your motor. So, high barometric pressure good, lower humidity good. Catch is when the humidity drops sometimes the pressure drops too. The air has less water and is therefore lighter. My methanol car run better if the pressure is over 1015. Hope this helps. Shouldn't affect your car too much at all as your computer compensates the mixtures and timing to suit the air.