National Hot Rod Association

Nowhere is the contrast in atmospheric conditions from one event to the next more prevalent than when the Full Throttle Drag Racing Series shifts from dry and high Firebird International Raceway in Phoenix, Ariz., to low and often humid Gainesville Raceway in northern Florida.

"You're going from a lot of altitude and dry conditions to almost no altitude and a ton of humidity," says Jimmy Walsh, crew chief for Toyota-supported Morgan Lucas, driver of the Geico Powersport/Lucas Oil Top Fuel dragster. "To me, it's actually easier to make the car run at Gainesville than it is at Phoenix. In a place like Phoenix, the engine is a little perkier. You have to be careful there because the engine really tries to hurt itself. And it makes so much more power that it can really be hard to control. The thing is, you run a lot more races at tracks like Gainesville. Probably two-thirds of the events we go to have humidity similar to Gainesville's.”

In often muggy, usually sunny Gainesville, home of this week's Tire Kingdom Gatornationals, track temperature can also be a major concern.

"You really have to watch it there, because the sun is usually shining, and the track can get pretty hot," explains Walsh, who earned his first victory as a crew chief in his first attempt, at the 2001 Winternationals, with the late Darrell Russell driving. "In the middle of the day, about the time you're running the second round of eliminations, the track temp can get up around 120 degrees. In Phoenix, it was only 75, and when the sun went down, it got way below that. You'd think that would be good, but track temperatures can get too low, too. I like it best when it's about 80, but anything above 70 and below 90 is fine."

For crew chiefs, the amount of water in the air isn't expressed simply as a percentage. To them, relative humidity is determined by the number of grains of water per pound of air, or, as crew chiefs say, simply "grains."

"Anything below 50 grains is considered dry," Walsh says. "Anything above that is wet, and anything above 100 is really bad. The worst I've ever seen was in Memphis a few years ago, when that race was in August: 130 grains. The cars don't want to run at all when there's that much water in the air. At the first two races of the year, Pomona and Phoenix, the grains varied from 20 to 50. When we get to Gainesville, it should be somewhere around 80."

For Brian Corradi, crew chief for Toyota-supported Antron Brown, driver of the Matco Tools Top Fueler, the amount of water in the air at a place like Gainesville is taken into account by some small tweaks to the baseline setup.

"Normally, we add a little timing for Gainesville, just a degree or two,” he says. “We also take a little fuel [nitro percentage] away from it and lower the static compression.

"Overall, Gainesville is almost always better than Phoenix," he adds. "Gainesville isn't always as muggy as people think it's going to be, because of the time of year we're running there. If it was in the summer, then it would be as bad as it is in Topeka – probably worse – but we race there in March. The barometer is always going to be better in Gainesville than it was in Phoenix. In Phoenix, it's usually 28.80 or 28.90, somewhere in there. Then you get to Florida, and it can be up around 30.0. If that's the case, you don't need as much compression. The closer you get to sea level, the less compression you need, at least with my tuneup."

"Every crew chief out there has his own way of doing things," Walsh says, "and probably no two guys are exactly the same. The way my program works, I decide what I'm going to do with the blower [overdrive] based on what the altimeter says. I look at the temperature to decide what I want to do with the compression. And I vary the ignition [advance] according to the number of water grains in the air.

"I have a baseline setup, a starting point, when we get to a race, but those are the things I look at when I make changes," he adds. "I try to never get too far off in any direction with any one thing. Basically, I see if the air is getting wetter or drier and go from there. The technology has changed a lot over the years, obviously, but we're all still trying to do the same thing. The computer is a great tool, but it doesn't give you the answers. Sometimes, all it does is create more questions..."