Air vs. Electric #1 stop?

[Chris Williams]

Typically, you check/set your "dead stall" (the amount of closure on the stop, which equates to an RPM) at the start of a weekend. It's most effected by altitude and general atmospheric conditions, so once a weekend is usually enough. We check ours, but it rarely needs to be adjusted -- once set, it's good.

There are a lot of opinions on what your dead stall should be. Some are fans of dropping just a little, and being on the stop longer, others feel just the opposite. I prefer to adjust it based on the time on the stop. My goal is from 1-2 seconds. You need time for the car to settle on that RPM, but not so long as the car starts to climb. Even when on the stop, a high-HP car will start to accelerate. You want to avoid that, as it detracts from consistency.

Once you find a good rate of on and off the stop, most people don't change it. Ever. You're trying to limit the number of variables. So you find a rate for each, where the tire spin is limited, and stick with it.

Then there are the key variables: time on and off the stop. Time on is another religious argument. We go on the stop immediately, at 0.0, but some consider that controversial. Others prefer something like 0.1 or 0.2. Some even like to mess with people's heads and go on the stop at the end of the track...

For most Super racers, you get a dead stall that works, a rate on and off that works, and a time on the stop that works, and stick with them. And just adjust the time off the stop. That time when you come off the stop is the key variable.

To initially set it, the best way is to run two runs in similar conditions, and have wildly different times, like 1.2 seconds and 1.8 seconds, and then do the math. You come up with a throttle stop ratio (e.g. 3:1, for every 3 hundredths of stop change, you get one hundredth of ET change). Now you know a number you can use to predict your stop time for the race.

Then you need to figure out how the weather effects your car. Many use density altitude, others use a horsepower correction factor, there's a lot of "special sauce" here as well. People will argue one vs. the other.

Then others, like me (a computer geek with 20+ years in the computer business) use computer programs to do the math. Some examples are Crew Chief Pro, my favorite Race Log Pro from ifamilysoftware.com, and I'm working on my own system for our use. They let you log the history of all your runs and make sophisticated analysis of the car's performance wrt the weather.

Long winded, hope this helps,
Chris