Time slips improve in a big way

Here's what we know for sure after the NHRA wrapped up four days of national time trials recently in Phoenix: Action started slow but heated up in a big way.

Time slips from the first day to the last showed stunning contrasts. When initial passes were made in Friday's opening rounds, tire smoke, tire shake, and early shut-offs were the norm.

In Top Fuel, Doug Kalitta led with a category-best 4.721-second elapsed time at only 252 mph -- far off the usual 4.50/330 pace indicative of this class. In Funny Car, Del Worsham's 4.792/323.27 run was the only 4.70's pass, but a host of other drivers were pleased with their test runs in the 4.80 to 4.90 range.

On Saturday, rain drastically shortened the test schedule but before time trials were halted defending POWERade Top Fuel champion Tony Schumacher and Brandon Bernstein each tallied a run in the 4.50's, while Gary Scelzi in the Oakley Hemi Dodge F/C ran the quickest fuel coupe pass with a 4.80/323.97 shot.

On Sunday, with improved track conditions on tap and teams using the data from their previous test runs to refine their tune-ups, performance took a swing in the right direction at day's end when Doug Kalitta ripped to a spectacular 4.497/327.43 in his Mac Tools Top Fuel dragster, easily the quickest and fastest run to that point.

In Funny Car, 13-time champion John Force rattled the clocks at Firebird Raceway with his 4.736/329.67 blast, that category's most impressive run after three days. What made Force's run sweeter was that his Castrol teammates, Eric Medlen and rookie Robert Hight, ran the second- and third-best passes of the weekend with their identical 4.743 elapsed times.

Adding some unexpected interest to the test proceedings was the appearance of two former Funny Car standouts -- Dale Pulde and Mike Dunn -- who were asked to fill in for the three Schumacher Racing F/C drivers (Whit Bazemore, Gary Scelzi and Ron Capps, who were all attending a function with sponsor Matco Tools). Pulde and Dunn, two old pros with years of drag racing experience, each made several passes in the three Schumacher-owned machines. Both drivers ran in the 4.80's, with Pulde's best lap coming in Scelzi's Dodge and Dunn's in Bazemore's.

One of the new wrinkles in the nitro classes -- the mandatory rev limiter -- is getting much attention from the Top Fuel and Funny Car teams in testing. The rev limiter will be required by the NHRA when the tour hits Gainesville, Fla., for the Mac Tools Gatornationals on March 17-20. The device will electronically limit engine RPM's during a race and hopefully decrease the likelihood of an engine explosion or oildown.

This weekend, the Strip at the Las Vegas Motor Speedway will offer the final formal slate of testing for the NHRA's nitro brigade before the season-opening Carquest Winternationals on Feb. 10-13 in Pomona.

Bill Stephens covers NHRA for ESPN.com.