Updated

The Sprint Cup and Nationwide Series are running under the lights at Bristol Motor Speedway this weekend. The IndyCar Series heads west to Sonoma Raceway, and Formula One is back in action with the Belgian Grand Prix.

NASCAR

Sprint Cup Series

Irwin Tools Night Race - Bristol Motor Speedway - Bristol, Tenn.

With three races to go before the regular season concludes, the pressure is on for many drivers in their efforts to make the Chase for the Sprint Cup championship.

Saturday night's race at Bristol Motor Speedway will be a pivotal one in determining who might make it into the playoffs and who might not. After Bristol, the Sprint Cup Series moves on to Atlanta (Sept. 1) before the Chase cut-off race at Richmond (Sept. 7).

Just 20 points separate seventh-place Dale Earnhardt Jr. from 11th-place Kasey Kahne, and 27 points divide 10th-place Greg Biffle from 15th-place Ryan Newman.

Kahne and Martin Truex Jr., who is 12th in points, currently hold the two wild card spots. Kahne won the spring race at Bristol in March and then scored his second victory of the season earlier this month at Pocono. Truex's win came in June at Sonoma.

"I don't like not being in the top-10, but I feel a lot more secure," Kahne said. "Our chances are a lot better because of the Pocono win. It was a big win. It was really good and helped our team out. These next couple of tracks are good tracks for us, so we want to race our way back in. We want to get those bonus points to start the Chase."

Kahne will attempt to become the first driver to score a season-sweep at Bristol since Kyle Busch last did it in 2009. A third win for Kahne this year would assure him at least a wild card for the Chase.

"The Bristol night race is always one of the better races of the year," he said. "It's one of the races I look forward to just because of the time of the season it is. I like racing there at night. It's hot. It seems like tempers kind of get out of control there at times on the night race, probably because it's hot and you're racing under the lights. We won the first one, and we ran really well there the last few times we've been at Bristol, so I'm looking forward to trying to get another win and sweeping the season there."

Joey Logano put himself in the Chase hunt after winning last Sunday's race at Michigan. Logano jumped from 16th to 13th in points. He also climbed to third in the wild card rankings.

With Tony Stewart having missed the past two races due to his fractured right leg, his teammate, Newman, has advanced to fourth-place in the wild card battle. Newman won last month's race at Indianapolis. Stewart-Haas Racing announced earlier this week that Stewart will miss the remainder of the season and Mark Martin will substitute for him in the No. 14 Chevrolet, beginning at Bristol.

Kurt Busch's third-place finish at Michigan was crucial in his hopes of qualifying for the Chase. Busch, who is driving the No. 78 Chevrolet for Furniture Row Racing this season, moved up two spots to ninth in points. He's only two points ahead of Biffle.

"This is tremendous," Busch said. "Jumping in with the Furniture Row guys last year, running six races together, got a lot of the bugs worked out. It allowed us to discover things about ourselves, some weaknesses on the team. Each section through this season, like every six races, we can lump them together and say that we've improved every time we've gone through a chunk of six races at a time.

"Now here we are. We're 23 races in, got three to go to get in the Chase. It's an amazing feeling to be in position right now, have a group of guys from Denver, Colorado, in the Chase right now. That's what we have to do, make sure when the door closes, the music stops, that we got a place."

Busch, his younger brother, Kyle, and Jeff Gordon lead all active drivers with five victories each at Bristol. Kyle started off this week of racing here with a win in Wednesday's Camping World Truck Series event.

Gordon, who is 14th in the point standings and sixth in the wild card rankings, has yet to win a race this season. His last victory at Bristol came in August 2002.

"I love this race, and I love this track," Gordon said. "This is one of the few tracks that when I get here, I usually make it a point to walk the track on Thursday night and soak it all in."

Dale Earnhardt Jr., who is Gordon's teammate at Hendrick Motorsports, also has not won this season. Earnhardt has struggled in the past two races and dropped from fifth to seventh in points. He finished 30th at Watkins Glen and then 36th at Michigan.

"I think we'll be all right," Earnhardt said of his Chase hopes. "We're not an 11th-place team. We're a top-5 team. We're consistent. We're more consistent than most. We've just got to shake this, whatever is going on. It's something different every time. We've got good speed and we've just got to keep our head up and keep working hard and things will be all right."

Jimmie Johnson, who presently holds a 41-point lead, is the only driver who has clinched a spot in the Chase. Clint Bowyer (second in points), Carl Edwards (third) and Kevin Harvick (fourth) can secure their playoff spots at Bristol. Anyone 97 points or more ahead of the 11th-place driver will clinch a top-10 spot in the Chase.

Forty-four teams are on the preliminary entry list for the IRWIN Tools Night Race.

Nationwide Series

Food City 250 - Bristol Motor Speedway - Bristol, Tenn.

Sam Hornish Jr. is back on top in the Nationwide Series.

After finishing third last Saturday at Mid-Ohio, Hornish reclaimed the lead in the point standings. He had led in points following the July 21 race at Chicagoland, but his 34th-place finish one week later at Indianapolis dropped him to fourth in the rankings. Hornish has finished either second or third in the past three races, which put him to the front again.

"It's exciting to be back on top of the points battle, though we still have a lot of racing in front of us," Hornish said. "This championship is shaping up to be one of the most competitive ever, as there are five guys with a legitimate shot at it. We know exactly what we need to do, and our team is hitting stride as we approach this last-third of the season."

The 2013 Nationwide season is now two-thirds complete, and Friday night's race at Bristol Motor Speedway is next on the schedule. Just 18 points separate Hornish from fifth-place Brian Vickers. Elliott Sadler is second in the standings, followed by Regan Smith and Austin Dillon.

Sadler is the only driver in the top-five in points that has won a Nationwide race at Bristol in the past. He won the spring event here in 1998 and 2012. Sadler is presently 13 points behind Hornish.

"Without a doubt, Bristol Motor Speedway is one of my favorite places to come any time of year," Sadler said. "One of the best moments of my career was winning here in March 2012, with my parents by my side. There is something special about being able to come and win at a track that I was a fan at first. My father would bring me here when I was a kid, and I would dream about racing around Bristol. This (No. 11 Joe Gibbs Racing) team has certainly had an up- and-down season so far, and we are getting down to the wire in this Nationwide Series championship hunt."

Hornish's best finish in four Nationwide races at Bristol is fourth, which came earlier this year. He finished 10th here one year ago.

Kyle Busch, Kasey Kahne and Brad Keselowski are those Sprint Cup Series regulars scheduled to compete in this race. Busch won at Bristol for the fifth time in March, which placed him in a tie with Kevin Harvick for most Nationwide victories at this track. Keselowski has won in each of his last four Nationwide starts this season (Richmond, Kentucky, Iowa and Watkins Glen).

Forty-eight teams are on the preliminary entry list for the Food City 250.

IZOD INDYCAR SERIES

GoPro Grand Prix of Sonoma - Sonoma Raceway - Sonoma, Calif.

The IndyCar Series is back on track this weekend at Sonoma Raceway after taking a two-week break.

With five races remaining, Helio Castroneves holds a 31-point lead over Scott Dixon and a 65-point advantage over defending series champion Ryan Hunter- Reay.

All 25 teams entered in Sunday's race participated in a test session at Sonoma. Chip Ganassi Racing drivers Dario Franchitti and Dixon topped the time sheets. Franchitti, the four-time series champion, made a lap around this 2.385-mile, 12-turn road course in 1 minute, 18.2945 seconds. Dixon's best lap came in at 1:18.3694.

A Ganassi driver has won the last four IndyCar races. Dixon claimed the victory in the inaugural event at Pocono and then scored a sweep in the weekend doubleheader in Toronto. Charlie Kimball is coming off his first career IndyCar win on Aug. 4 at Mid-Ohio.

Franchitti has turned his season around with top-four finishes in the previous four races. He has moved up to sixth in points (-111). Franchitti started the season with back-to-back 25th-place finishes at St. Petersburg, Fla. and Birmingham, Ala. He also placed 23rd in the Indianapolis 500.

"It's nice to show the results that we've deserved," Franchitti said. "Earlier this year when we did have fast cars, we weren't getting the results. We've managed to turn it around a bit. Recently, we've had the form to get that first win of the season. Sonoma is as good a place as any to try and get that done."

Franchitti has finished no worse than eighth in his seven races at Sonoma. He won here in 2009.

Sonoma has been one of Will Power's best tracks in IndyCar. Power won at this course consecutively from 2010-11. Last year, he finished second to Ryan Briscoe, who was his Team Penske teammate at the time. Power also has won the pole here in each of the last three years.

"Sonoma is definitely a good chance for us," Power said. "It's a track I've had a lot of success on. Although the competition has definitely heated up this year, we still expect to be running right at the front."

Power is 11th in the point standings after finishing second in the series championship the past three seasons. He has not won a race since April 2012 in Sao Paulo, Brazil. Power is hopeful of a win this year and plans to help Castroneves, his teammate, in his efforts to win the title.

"It would be really nice to get a win before the end of the year," Power said. "As far as Helio goes, he's in a very good spot to win the championship, and as a team, we'll be doing everything possible to make that happen."

Castroneves won at Sonoma in 2008.

Briscoe is scheduled to drive the No. 4 car for Panther Racing at Sonoma. He has been behind the wheel of that car in five races this season, finishing no better than 13th. Briscoe fractured his right wrist during an accident in the first Toronto race and was unable to compete in the second event there.

"I'm obviously very happy to be back with the team and in the National Guard car," Briscoe said. "My wrist held up pretty good during the test, although the (wrist) brace was a bit of a nuisance. But we made good progress during the test and worked through our program really well. I was pleased with our pace and definitely looking forward to coming back to find more speed."

FORMULA ONE

Belgian Grand Prix - Spa-Francorchamps Circuit - Spa, Belgium

Summer vacation is over for Formula One teams.

After a three-week break, F1 begins the second-half of the season with this weekend's Belgian Grand Prix. Sebastian Vettel from Red Bull enters round 11 of the 19-grand prix season with a 38-point lead over Lotus' Kimi Raikkonen. Fernando Alonso from Ferrari is 39 points behind, while Mercedes' Lewis Hamilton trails by 48. Hamilton won the most recent grand prix on July 28 in Hungary. It also was his first victory with Mercedes.

"It feels like I have been out of the car for a very long time since the win in Hungary, and I can't wait to get going again," Hamilton said. "We're all looking forward to the second half of the season and the opportunity to bring home some more good results."

Vettel is attempting to win his fourth consecutive F1 world championship. He leads all drivers with four wins this season (Malaysia, Bahrain, Canada and Germany, his home country). Vettel won the Belgian GP in 2011 and finished in this event last year.

"I think we had a great first part of the season," Vettel said. "Now entering the second half and looking at the calendar, I think it will be very busy for all of us, but I think we have the same reason to be confident as we had starting the season. I think we have a great car, a great team, a strong package, which hopefully is good enough to fight for victories in the next couple of races."

The Belgian GP is contested on the 4.352-mile, 19-turn Spa-Francorchamps circuit, which is one of the fastest tracks on the F1 calendar. Jenson Button is the defending race winner, but the McLaren driver has struggled this season, as he sits ninth in points (-133). Button's best finish this year is fifth, which came in the Chinese Grand Prix.

"The thing about Spa is that it just feels awesome to nail a quick lap around there," Button said. "You need a car that's perfectly synced to the driver, because it's such a long lap and there are so many big corners that you need to find that perfect balance. And getting the set-up right and running flat- out for nearly two minutes feels incredible. We don't go to Spa with the package to win, but I'll still be making the most of every single lap around this place. It'll still feel incredible."

Raikkonen leads all active drivers with four wins in the Belgian GP.