AJ Foyt Racing's technical director Mike Colliver says Sebastien Bourdais' talent, experience and attitude, and the engineering group "pulling in the same direction", has resulted in the IndyCar team's improvements.
Bourdais, who joined AJ Foyt Racing part-time for 2020 and is a full-timer for '21, topped this week's 12-car test at Barber Motorsports Park when laps using the push-to-pass boost were taken out of the equation.
This follows a strong test at the same venue last November, and a fourth place in the 2020 season finale at St. Petersburg - a result the team hasn't bettered since Takuma Sato scored a podium at Detroit more than five years ago.
Encouragingly, Dalton Kellett, who will drive the #4 Foyt car full-time this year, ended the test just 0.7s slower than Bourdais, who has four Champ Car titles and 37 race wins to his name.
Colliver, who became the team's technical director after hiring Justin Taylor to serve as race engineer on Bourdais' car for this season, said: "I think the test is just the continued development from some of the stuff we were doing at Road America last year.
"Charlie [Kimball, this year Foyt's third driver for Indy GP and Indy 500] was pretty strong in Race 2 and Dalton was strong at Mid-Ohio for where his development is.
"We then had a really good test at Barber in the fall with Sebastien, and some of that was combining what was done in the past, ideas that I brought, ideas that Mike Pawlowski [race engineer on the #4] had.
"COVID and the compressed schedule has helped us catch up and gave us the time to have in-house development of some of the tools we could use to analyse and quantify things. The test was a good validation for some of those tools."
Regarding Bourdais' contribution, Colliver said: "He's a huge help. Just his wealth of knowledge is a huge help from a couple standpoints.
"One, he understands mechanically what the car is doing, and secondly, he gives the changes to the car a fair shot. He will go out and run six or seven laps, and maybe the first two laps it doesn't feel great. Maybe he'll change something in his driving style or he'll wait a little longer for the tyre pressures to come up or do a click on the rear bar - whatever he needs to do. And then he comes in and tells you it either worked or didn't and why.
"His analytical approach combined with his experience is really refreshing. He doesn't get rattled, he's very calm and meticulous in the car.
"But it is also the whole feel of the group. The engineering group is really working together well. Everybody is putting work in that shows up on both cars and really on Seb's because of his driving ability.
"From the data guys, to the guys who are doing simulations, the junior engineers, Danielle's (Cucchiaroni, performance engineer) knowledge and Justin is doing a great job. Everybody is pulling in the same direction which is really cool."
Bourdais added: "We went through a lot of stuff, testing dampers and some concepts as far as platforms. Everybody's starting to work pretty efficiently together, the atmosphere is good.
"The car was pretty quick right out of the box and I had a really good time. Very positive day. With Barber being the season opener, you want to be cautiously optimistic. I think we should have a good card to play and be in the mix, which is always encouraging, so I'm looking forward to it."
The team has one more test planned at Texas Motor Speedway at the end of March before the Open Test at Indianapolis in early April.