some drag racing factors...

[tenji]

These were good reads...

http://www.8thcivic.com/forums/auto...ect-your-1-4-mile-time-newbies-must-read.html

Factors that will affect your 1/4 mile time: Newbie's must read!!!
Ok everyone. Just as some background about myself, I'm a 23 year old who had the fortunate luck of growing up with a father who owned a very successful drag strip for 22 years (New York International Raceway Park in Leicester, NY near Rochester). Over the years I've gained insane insight into the world of drag racing, some of which most average or inexperienced racers would never know or even consider to be a factor in your times. Here's some, and please do add if I missed anything.
1. WIND
Most racetracks have an American Flag a flyin'. My father had one right next to the starting line. It wasn't happenstance... he put it there so that racers could look to see the wind direction and roughly how fast it was moving. A headwind slows down cars up to two to three tenths (thats like a 15.0 vs. a 15.3) Crosswinds (perpendicular to the car) can also slow you down, and a tail wind can help you gain speed and lower ET. Remember this and take note when you run!

2. Heat/Humidity
I have a degree in meteorology and in a bunch of physics classes I really got to figure out how heat and humidity affect motor performance. Heat is the number one power reducer, which is why we are always trying to eliminate it (TBS, COLD air intake, interCOOLERS). A hot day will slow the car down, its just how it works. Consequently, too cold will also have adverse effects.

ALSO, and even some advanced racers may not know, but tracks have an ideal temperature as well. Traction compound turns to sludge when its too hot, especially when the sun is overhead. Most of the fastest runs occur after 3pm or so, or even near dusk, when the track isn't sucking in all the light from the sun. Ideal track temp is about 68 degrees or so, which means early or late season for most. Now this effect with street tires is far less that those with 500hp, and slicks, obviously.

Humidity, you simply want less. The more humid it is, the less oxygen there is, the lesser the "quality" air going into your car.

3. WEIGHT
I've seen people take out spares/seats etc. Maybe even go on a diet? LOL. What about gas? I see so many people show up to the track with a FULL tank of gas. FYI, a gallon of gas weighs 6.18lbs. Our fuel capacity is 13 gallons. You do the math... but I don't like an extra 60 lbs in my car if I don't need it. Figure out the mileage to the track and then leave home with the bare minimum for your truly ideal times.

4. I think that if you post on here, especially for newer or more inexperienced people... you should list all applicable mods, the RPM you launch at, and whether you power shifted or granny shifted. Some people don't know how or aren't willing to power shift and that is pretty much the difference between the 15.2 guys and the 14.9's stock.

5. Altitude
Some tracks will be able to tell you, or you can find an experienced racer in the pits with the handheld computers that give you the altimeter. This also effects engine performance based on air density most of the time. Higher pressure will usually give you a better running car. Consequently, high pressure usually means sunny days too!

6. For our cars (Si's etc.), unless you are putting down insane horsepower, there is NO NEED to roll through the water. I go right around. You're immediately giving yourself a disadvantage by dirtying the tires and wetting them. Heating them up will take off miles that they could be used for, and will give you a negligible effect if any. Just get better tires in this case.

7. Tire pressure
How many of you have a pressure gauge in your glove box at the track? How many use it? This is HUUUUUGE when dealing with traction/top speed/etc. Check tire pressures and play with them to find your ideal spot. You want a balance between traction and top speed. Experiment! Most tracks have free air somewhere on sight ( or make buddies with someone who has an air tank!)

8. Talk to other racers
There is ALWAYS someone who knows more than you. Lanes at certain tracks can make a huge difference. At my dad's, the right lane is always faster for some reason. That could be a huge difference.

9. Analyze and PRACTICE, PRACTICE, PRACTICE!
Read the time slips at each part. Figure out what they mean if you don't. Compare with others on the board to see where you are and where your weaknesses are. This will tell you what you have to work on. MPH and 1/4 time can't be their best until your 60', 330', 660' and 1000' are perfected!

I hope this gets you started on your way to drag racing. I strongly urge anyone to try it out if you haven't before. It's safe, fun and god I love the smell of the track. Good luck!

and

http://www.clublexus.com/forums/showthread.php?t=384802

Drag Strip times and Density Altitude (statistical analysis)
I did this a couple of weeks ago, I just didnt have the time to post this.
Thanks to Caymandive I was able to get some information form his drag strip journal and use it to answer some questions that i had about drag racing in the IS350... So using a a statistical software i ran some tests.

the main variable taken into consideration was density altittude (DA)..... I wanted to know, not only if DA affects 1/4 mile times(because it obviously does), but by how much. and what times to expect on 1/4 mile on my IS350 according to the weather conditions.
It is hard to explain what density altittude is, but it is basically an international standard of measuring the density of the air, humidity, elevation, and altimeter, all into one number. the lower the density altittude the faster the car will be (basically). usually the lower the temperature is the lower DA is.

So I ran a regression, which is a statistical analysis that lets you forecast 1/4 mile times (in this case) and answer other questions.
From caymandive's journal, I took all the 1/4 mile times and their respective Density Altutudes at the time of the runs. I only took IS350's I did not take IS-F times. otherwise this test would be pointless.

Here are the results:

Regression Analysis: 1/4 mile time versus DA
The regression equation is
1/4 mile time = 13.4 + 0.000137 DA

Predictor Coef SE Coef T P
Constant 13.3584 0.0258 516.78 0.000
DA 0.00013677 0.00002112 6.48 0.000

R-Sq = 53.8%

Analysis of Variance

Source DF SS MS F P
Regression 1 1.0086 1.0086 41.93 0.000
Residual Error 36 0.8659 0.0241
Total 37 1.8745


So, what do these numbers mean:

Question: Does density altitude have an effect on mile times?
Yes, Density altitude does has an effect on mile times. Density altitude has a positive effect on mile times, which means that as density altitude goes up, so do mile times. And as density altitude goes down, so do mile times.
There is only five percent chance that we have answered this question wrong, so we are 95% sure that these statements are true.

53.8% of the variation in mile times can be explained by density altitude. The other 46.2% is explained by other factors such as: track conditions, drivers skill level, weight reductions, tire psi, quality of tires, gas, etc.
So basically, 53.8% of your 1/4 mile time you can say its due to Density Altittude. the other 46.2% you can say, well this track sucks, or Im not a good driver, or my tires are old. blah blah, etc.

What times can I expect by looking at a specific DA number?
With density altitude at 0 feet, the Lexus IS350 should run 13.4 1/4 mile E/T time.
For every 1000 feet change in DA, there is a .13 second change in mile times.
Example: You should run 13.40 @ 0 feet of DA.
You should run 13.27 @ -1000 feet of DA.
You should run 13.53 @ 1000 feet DA.

This is how you can estimate your 1/4 mile time before going to the track by looking at the density altittude.

example: if density altittude is -700......
you use the regression equation = 13.4 + .000137(-700) = 13.30 E/T time
So, basically with Density Altitude at -700ft. I should run 13.3 on the 1/4 mile. anything lower than that is a good time.