Nearly half a second behind rookie team-mate Marc Marquez during the opening day of the Austin MotoGP test, Dani Pedrosa reduced the deficit to just 0.123s during day two.
Pedrosa worked on gearing and rear suspension settings for his Repsol Honda and beat his best Tuesday lap by over one second.
"Today we continued to put in laps and I was also able to improve my cornering on some turns; I found some details that allowed me to run a better line on them,” said the 2012 title runner-up.
“We had good conditions and were able to try some different gearing, plus a couple of shock absorbers that allowed us to gain a little more grip.
“We made the most of the second part of the day, in the afternoon, as the track was much better than in the morning. We are happy with how the second day went and hope to continue with the good work tomorrow."
Pedrosa has been faster than Marquez at all three previous tests that they have both attended.
0.375s behind Pedrosa on Wednesday was the leading Yamaha of reigning champion Jorge Lorenzo. Lorenzo and team-mate Valentino Rossi will not test on day three.