INDIANAPOLIS – Scott Dixon finished the second day of practice for the 104th Indianapolis 500 as the fastest man at the track, but the real speed demons will be decided during Fast Friday.

IndyCar adds additional boost to the turbochargers beginning Friday and through the weekend of qualifications that will determine the order of the 33-driver starting lineup for the 104th Indianapolis 500 on Aug. 23.

The extra boost creates an additional 40-50 horsepower, which means speeds are expected to easily soar past 230 mph beginning Friday.

“It’s going to be cool,” Dixon said. “It’s a big jump (in power). We’re pretty low speeds (today). I expect to see some pretty big speeds tomorrow, especially in tows. Everybody will be trying to get a clear track, but that’s going to be tough to get. I’m excited for tomorrow – Fast Friday.”

Dixon, the 2008 Indianapolis 500 winner and a five-time NTT IndyCar Series champion, was the fastest driver in Thursday’s practice session with a fast lap at 226.102 mph in the No. 9 PNC Bank Honda.

“Today, we made some minor changes and tried to figure out some different balances,” Dixon said after the six-and-a-half hour practice. “We’re also focusing on how the car feels. The No. 8 car had some changes yesterday that (teammate Marcus Ericsson) liked and we tried them, but I’m on the fence. We’re just running through those variations and trying to run in as much traffic as possible and get the car as comfortable as possible for the race.

“We’re really just working hard on race setup. We’ve had a lot of options to work through, and we also wanted to run some of the things the other two cars have tried. We also worked on finding traffic today to see how the car would respond.”

Takuma Sato, the 2017 Indianapolis 500 winner, was second quick at 225.693 mph in the No. 30 Honda for Rahal Letterman Lanigan Racing. Marco Andretti of Andretti Autosport was third at 225.249 mph in the No. 98 Honda followed by Conor Daly’s No. 47 Chevrolet for Ed Carpenter Racing at 225.106 mph.

Spain’s Alex Palou rounded out the top-five at 224.971 mph in the Dale Coyne Racing with Team GOH Honda.

Fellow Spaniard Fernando Alonso crashed with 45 minutes left in practice, when he went low in the center of turn four, which sent his No. 66 Chevrolet into the turn four wall. His care slid across the track and came to a stop near the Dreyer & Reinbold pits at the north end of pit road.

The car suffered moderate damage in the incident.

Alonso, who also crashed in practice last year, was eighth fastest Thursday at 224.363 mph before his accident.

“Hopefully it happens today instead of Sunday the 23rd,” Alonso said. “You learn every lap you do around here, and we learned from this. Tomorrow we start again. I think everything tomorrow is going to be OK. Let’s keep up the good work, and hopefully no more issues.”

As for Fast Friday and the extra boost, Sato said the additional speed is quite noticeable early in the session when drivers are entering turn one at a much faster speed than throughout the week.

“The first time you will notice out of the turn two after pit lane, you’ve got acceleration,” Sato explained. “The acceleration never stops basically. It’s really, really high. Every single turn seems to be much narrower because it’s, let’s say, tunnel vision. You go faster, it is harder.

“I think once you get used to the rhythm, you will enjoy the sensation. Every time new tire, new tire. That’s why it’s really good practice to get used to the speed and sensation. After the qualify, you go back to the race boost and downforce, (it) is so much easier after that.

“First of all, you will find it very challenging, particularly tomorrow we will have unknown. We will have up to 160 for the boost, which is the most powerful we ever felt. The aero efficiency is not as good as last year, means more challenging into the corner.

“I don’t know how much we can actually trim. Last year we went to the minus nine degrees. I don’t know if this year’s car we can go that way.”

Palou, a 23-year-old rookie, will go faster than he’s ever gone in his career to date.

“I’m looking forward, excited for that,” Palou said. “I was real excited yesterday before going out on track. It felt quicker than I thought. Yeah, I think tomorrow is going to be, as Takuma said, the most power we had. It’s going to be a big difference.

“Let’s see how it goes. I don’t know how much speed we are going to gain. Today we saw that people is already doing 225. I think we going to go well over 230s on qualifying, and that’s going to be tricky.

“Good thing is that we have full day tomorrow just to prepare the car for qualifying. I think that we showed, and the team progressed a lot, when we have track time. I think it’s going to be a good day tomorrow as well.”