Worryingly for the Honda camp, two of their line-up of cars were sidelined during the day. Michel Jourdain Jr.'s Rahal Letterman Lanigan car suffered an engine problem just 55 minutes into the session, crawling to a halt on the backstretch with smoke and flames visible.
"Not such a good day," admitted Jourdain. "Unfortunately we had a problem early on and we didn't run many laps ... I felt a loss of power, and the guys told me to shut it down. I don't know what they saw in the telemetry, but they told me to shut it down. Then I saw smoke, so there was a fire.
"It was our first run, and we were just starting to trim the car," he added. "I could definitely feel the difference in power with more boost. It was fun to drive."
Panther/Dreyer & Reinbold's Oriol Servia feared the same thing had happened to him early in the session, only to find that the problem wasn't solved by replacing the engine after all.
"Obviously, it was not in our plan nor was it our ideal day because we wanted to get a feel of the car," said Servia. "We started the car, and we saw some smoke and thought it was the engine. We rushed to change it to try to get out on track. When we put in the new engine, it was still smoking just as much, which we then discovered that it didn't have anything to do with the motor."
The remainder of the top ten consisted of 2011 Indy 500 runner-up JR Hildebrand who was eighth in the Panther Racing car with a lap of 225.571mph (39.8987s) and KV Racing Technology's Tony Kanaan in tenth (225.322mph, 39.9428s).
"We feel pretty good - we'd like to find a little more speed in the National Guard Chevy, but we more or less accomplished everything we set out to do today," said Hildebrand. "Now it's just a matter of trying to figure out what our target speed will end up being when Pole Day comes around tomorrow."
The two Lotus drivers, Jean Alesi (Fan Force United) and Simona de Silvestro (HVM Racing) were once again significantly slower than any of the other cars out on the track on Friday. Both cars had received a 'sneak preview' of the turbo boost earlier in the week - which had helped Alesi achieve the speeds required to complete his Rookie Orientation Program - but even so were around 2mph better than their previous boosted best speeds of the week, showing definite progress.
"We have been getting better day after day, and doing what we have to do, and now the next thing we have to do is qualifying, as we prepare for the race," said Alesi, sounding happier than he had done mid-week. "The balance on the car is good ... I feel we have a good car under us, and I could notice the horsepower change we had in the engine."
"A pretty good day," agreed de Silvestro. "We made progress and found a little bit of speed. I think we should be all right for qualifying."