The top-seeded American made light of trying four-to-six foot (one-to-two metre) surf as he scored 11.56 out of a possible 20 to book his place in the last eight.
“I was really relieved to get through it,” Dunphy said. “Today is probably the most closed out the conditions have been and I was just able to get in to a good rhythm in the beginning.
“I was able to find a couple that let me do a couple of turns and that really set me up for the rest of the heat. I was happy to get through because it was my hardest heat so far.
“I figured I’d just do my thing and try and get those lefts and do what I’ve been doing.”
Tudela also progressed after finishing second in the heat.
Promising 20-year-old Tanner Hendrickson also booked his place in the quarter-finals after beating Colin Moran, Diego Cadena and Dane Anderson.
The Hawaiian, who has been impressing on the ASP Pro Junior Series and is beginning to enjoy success in the major men’s ASP events, admitted the conditions were tough at Playa Revolcadero.
“I’m stoked to get that heat win,” Hendrickson said. “You’ve really got to find your peak and surf really down the line the whole time because the wave is breaking so fast.”
“I’m so stoked to make it to the man-on-man Quarters. With the man-on-man heats, I’m definitely going to try and be more patient and try and sit away from the other competitor and find my own peaks.”
QUIKSILVER SURF OPEN ACAPULCO ROUND OF 16 RESULTS:
Heat 1: Tanner Hendrickson (HAW) 11.60, Colin Moran (USA) 8.24, Diego Cadena (MEX) 8.10, Dane Anderson (USA) 7.57
Heat 2: Michael Powell (USA) 11.10, Gavin Gillette (HAW) 6.47, Jose Trujillo (MEX) 6.16, Jeffrey Lukasik (USA) 5.47
Heat 3: Michael Dunphy (USA) 11.56, Miguel Tudela (PER) 7.90, Shane Beschen (USA) 7.76, Cory Arrambide (USA) 5.13
Heat 4: Leigh Sedley (AUS) 8.80, Carlos Munoz (CRI) 8.56, Hank Gaskell (HAW) 8.44, Taylor Clark (USA) 6.20
QUIKSILVER SURF OPEN ACAPULCO ROUND OF 32 RESULTS:
Heat 5: Michael Dunphy (USA) 10.83, Taylor Clark (USA) 7.60, Manuel Selman (CHL) 7.54, Rafael Pereira (VEN) 2.87
Heat 6: Cory Arrambide (USA) 11.60, Carlos Munoz (CRI) 10.17, Alan Saulo (BRA) 7.56, Jean Schaffer (VEN) 2.74
Heat 7: Leigh Sedley (AUS) 10.90, Miguel Tudela (PER) 8.04, Ricky Whitlock (USA) 6.50, Chris Tucker (USA) 5.53
Heat 8: Hank Gaskell (HAW) 10.33, Shane Beschen (USA) 9.63, Ian Crane (USA) 8.67, Dege O’Connell (HAW) 4..53