With qualifying weekend imminent, the big teams and star drivers were increasingly showing their confidence and their game plans on Thursday in a shortened five-hour Thursday afternoon practice at the Indianapolis Motor Speedway, which had to fit around the first runs out on track for Dragon Racing breaking in their brand new Chevrolet engines.

Scott Dixon put the Honda-powered Ganassi at the top of the timesheets for the first time since the practice started last Saturday, with a lap of 223.088mph (40.3428s) once again with the help of a little tow in traffic.

"We're just working on the race car, and I think we've made big improvements on how it feels," said Dixon. "For me, I feel happy because we made the car feel a lot nicer to drive, and especially in traffic it pulls up better, I think.

"These speeds are all big tows, so it doesn't really matter much," he added. "Tomorrow and Saturday are going to be totally different stories to see who's got what out there by themselves, so that will be interesting. But all in all, I think Honda and Team Target are doing pretty well."

Sarah Fisher Hartman Racing rookie star Josef Newgarden continued to impress by holding on to second place in the times with a lap of 222.709mph (40.4115s) just 0.0687s off Dixon's best lap.

"We've had a great week, and we just need to continue what we've been doing," said the 21-year-old. "Today we only worked on race setup. We'll start back on qualifying tomorrow when we get the boost. We just picked up today where we left off yesterday and continued working in the race direction."

The Ganassi squad were clearly stepping up a gear and starting to reveal their true pace on Thursday, with all four of their cars in the top ten by the chequered flag: Graham Rahal was in third (222.080mph, 40.5259s), Dario Franchitti eighth (221.344mph, 40.6606s) and Charlie Kimball ninth (221.321mph, 40.6649s).

"A great day," enthused Rahal. "We worked on a couple things we needed to, we found out a lot. We worked on our race cars, and we're pretty happy with it. We're excited to move on and work on some qualifying stuff. Come Sunday, when we get back to race trim, I think we're going to have a good car."

"We had a pretty good car last night, and we tried a lot of different stuff today and managed to make it worse!" admitted Franchitti. "Right at the end there, we made a couple of changes and got it better again. I think we're probably back to where we were last night, which is not a bad place."

"We had another productive day of race simulation, ran a couple of sets of tyres and made some good progress," added Kimball. "It was great to be out there with my teammates."

Ganassi's big rivals in the IZOD IndyCar Series championship, Team Penske, were also perking up as qualifying weekend loomed, with Will Power the top-placed Chevrolet-powered car in fourth place (221.932mph, 40.5529s) and his team mate Ryan Briscoe finishing the day with the sixth fastest lap (221.510mph, 40.6302s).

"It was our last chance [until Sunday] to try race setups and understand what the car does in traffic," said Power. "We did two full runs, basically."

"Not a bad day, really," added Briscoe. "It was nice to get more running in after a quiet Wednesday. We did a lot of race setup work with our IZOD car today, and we are learning a lot, finding more of the things we will need come Race Day."

The only other Chevy runner in the top ten on Thursday was Panther Racing's JR Hildebrand, last year's Indy 500 runner-up, who posted a best lap time of 221.022mph (40.7200s) to finish in in tenth place. The remaining places in the top ten were taken by Justin Wilson - who continued to look strong for Dale Coyne Racing in fifth place with a best lap of 221.715mph (40.5927s) - and AJ Foyt Racing's rookie driver Wade Cunningham, who was seventh fastest of the day with a lap of 221.450mph (40.6413s).

"We rolled out full race setup," explained Cunningham about the team's approach to the day. "It was the first time we'd run full tanks, so we matched tyres with the fuel loads, full race downforce. We made some attempts at it yesterday, but we improved the gearing a little bit for the race downforce."

The top ten were helped by the team that had dominated much of practice so far this week - Andretti Autosport's five-car squad - largely putting its feet up on Thursday, having already accomplished everything that they wanted to ahead of Fast Friday. Ana Beatriz put in only 14 laps and Ryan Hunter-Reay simply put in a quick installation tour without setting a representative time, while Sebastian Saavedra and Marco Andretti didn't come out at all.

James Hinchcliffe also only made a token appearance out on track, explaining later: "We always knew we were going to get on track late today. I think we were hoping to get on track and get at least one real run or two getting ready for tomorrow with proper boost, but we had a small problem that we found and we wanted to make sure everything was right before we hit the track properly.

"We only got out for an install today, but that means the GoDaddy car is ready to rock tomorrow with the extra boost - and that's when it's really going to matter," he added.

The usual six-hour session had been reduced by an hour in order to allow the Dragon Racing team more track time following their late clinching of an engine deal with Chevrolet following their bitter split with previous engine suppliers Lotus.

The team started with a specially scheduled 90 minute session first thing, during which time Sebastien Bourdais shook the car down, helping to set the car up from a seriously shaky start first thing. Once things started settling down, Bourdais went on to comfortably complete two thirds of the refresher program he'd been asked to do given that it's been seven years since he last raced here.

"It's great to be back, but if you had asked me that this morning, I would have had a different answer," the Frenchman said. "We had something that completely messed the car up, and it made for the toughest car that I've ever driven.

"I'm just glad we found the reason and now we are good to go," he continued. "The car is easy to drive and has a good balance. We can drive flat out and not even think about it, which is what you want around here. Pretty happy with that."

That left the team with insufficient time in the morning to put Katherine Legge out on track to attempt her mandatory Rookie Orientation Program, and so the team were then given an additional hour from noon and a follow-up 40 minute slot after the main practice wrapped up at 6pm in order to get the British driver through phases 1 and 2 of ROP, which she did without incident - even needing to be told to slow down by the team to fit within the 205-210mph window for phase 2. In total, she ran 77 laps on Thursday.

"It's unbelievably satisfying," said Legge of finally getting her chance to run at IMS. "This morning, we had a small issue with the car, but we were still able to complete the first phase," she added, giving thanks to the team and also to her team mate for his set-up work: "He shook down the car and made sure everything was fixed from this morning. I can go home now very happy."

Now that Legge has completed the first two phases she will be able to run with the rest of the cars on Fast Friday to finish off ROP with phase 3 in time for Saturday.

The Lotus-powered duo of Jean Alesi (Fan Force United) and Simona de Silvestro (HVM Racing) were once again the slowest cars of those that did set flying lap times, although Alesi's time was certainly improving.

"I tried to follow some cars. I feel happy to run with cars. Less lonely!" he laughed. "Now tomorrow we have to prepare for qualifying. Every day is new for me, so I go step by step."

De Silvestro was also feeling a bit more buoyant. "Today we tried a little different setup, and it was pretty good. I think we found a little bit of speed," she said. "We're just working through the program, and I think it was a good day. We know where we are. We're just taking it slow and getting ready for qualifying to get in the show."

There were 29 cars out on track on Thursday during the practice session, not including Katherine Legge in her two separate rookie orientation solo sessions. Rahal Letterman Lanigan's Michel Jourdain Jr. put in the most laps during the day with 92 circulations. There were three cautions for a total of 22 minutes, all for debris with no spins or accidents.

Fast Friday should see times around 4-5mph faster than previously, with all teams able to make use of an extra 40-50 horsepower turboboost to the 2.2-litre V6 engines for the first time which will last throughout the weekend. The weather forecast for the next three days continues to look perfect for track activity, with no rain forecast through to Sunday.

Saturday sees the main part of qualifying for the Indy 500, with Sunday left for 'Bump Day', although with only 33 cars on the entry list at this point it seems that there will be little bumping in evidence this year and race organisers are reportedly discussing what to do with the Sunday format in order to continue to make it interesting for fans and spectators.

The Indy 500 itself starts at noon local time on Sunday, May 27.

Full practice 6 times available.