Takuma Sato says his car is still “not entirely happy” in a pack despite setting the pace on both days of practice running so far at the Indianapolis 500.

Sato topped the speed charts on Day 1 with a 228.939mph (368.442km/h) thanks to the help of a tow, and was the pace-setter again in the latest, six-hour session, when he went as fast as an average 227.519mph (366.156km/h) around the 2.5mi (4.0km) circuit.

However, he is still less than satisfied with how the #51 Dale Coyne Racing w/ RWR Honda feels when running in a bunch of cars.

“We’re working on it,” Sato said.

“The car’s not entirely happy in a big pack. Still, there’s work to be done.

“The boys are doing such a meticulous job, with great engineering. I’m happy with the progress, step by step, and here we are.

“Hopefully we have more to come.”

On the no-tow rankings, however, Sato was only 29th, although he was unfazed considering Fast Friday is next, when the boost will be turned up for genuine qualifying simulations.

By way of contrast, Andretti Autosport’s Alexander Rossi was fourth-quickest without a tow, but 28th overall on the latest day of action, yet happy with where his #27 Honda is at.

“I don’t even know how many people have done a no-tow, to be honest … I think it’s okay,” said the 2016 Indy 500 winner.

“The car feels really good. Forget about the speed that it does; the balance in the majority of conditions… it feels really, really nice.

“The whole Andretti Autosport organisation yet again has shown up for the Month of May and I feel good about the opportunity we have over the next two weekends.”

That comment is arguably counterintuitive considering the top Andretti entry was that of Marco Andretti in 15th, although Rossi was buoyed by how stable his car was on a day when others found the conditions tricky.

“I think the wind… You know, you can get a gust and it can give you a weird feeling,” he added.

“You can’t read into that too much – you’ll be chasing something that you’ll never find – so you’ve just got to find a car that generally, for most of the lap, you have confidence in.

“It’s not going to be perfect the whole day in every corner, but you’ve just got to have a car you have confidence in and right now we have that.”

Fast Friday gets underway tomorrow at 02:00 AEST, while Stan Sport has live and ad-free coverage of qualifying from Sunday morning (AEST).