diff --git a/klippy/extruder.py b/klippy/extruder.py
index e49d4c91..fc20ccf8 100644
--- a/klippy/extruder.py
+++ b/klippy/extruder.py
@@ -38,6 +38,7 @@ class PrinterExtruder:
         self.need_motor_enable = True
     def check_move(self, move):
         move.extrude_r = move.axes_d[3] / move.move_d
+        move.extrude_max_corner_v = 0.
         if not self.heater.can_extrude:
             raise homing.EndstopMoveError(
                 move.end_pos, "Extrude below minimum temp")
@@ -60,30 +61,34 @@ class PrinterExtruder:
                 return 0.
             move.extrude_r = prev_move.extrude_r
         return move.max_cruise_v2
-    def lookahead(self, move_info, orig_flush_count, lazy):
-        if not self.pressure_advance:
-            return orig_flush_count
-        min_corner_v2 = max_corner_v2 = 0.
-        flush_count = len(move_info)
-        for i in range(flush_count-1, -1, -1):
-            move, start_v2, cruise_v2, end_v2 = move_info[i]
-            reachable_start_v2 = end_v2 + move.delta_v2
-            # Calculate min/max_corner_v2 - the speed the head will
-            # slow to due to junction cornering and the maximum speed
-            # the head will reach immediately afterwards.
-            move.extruder_min_corner_v2 = min_corner_v2
-            move.extruder_max_corner_v2 = max_corner_v2
-            if reachable_start_v2 > start_v2:
-                min_corner_v2 = start_v2
-                if (start_v2 + move.delta_v2 > end_v2
-                    or end_v2 >= move_info[i+1][2]):
-                    if lazy and max_corner_v2:
-                        flush_count = i
-                        lazy = False
-                    max_corner_v2 = cruise_v2
-        if lazy:
-            return 0
-        return min(flush_count, orig_flush_count)
+    def lookahead(self, moves, flush_count, lazy):
+        pressure_advance = self.pressure_advance
+        if not pressure_advance:
+            return flush_count
+        # Calculate max_corner_v - the speed the head will accelerate
+        # to after cornering.
+        for i in range(flush_count):
+            move = moves[i]
+            if not move.decel_t:
+                continue
+            cruise_v = move.cruise_v
+            max_corner_v = 0.
+            sum_t = pressure_advance
+            for j in range(i+1, flush_count):
+                fmove = moves[j]
+                if not fmove.max_start_v2:
+                    break
+                max_corner_v = max(max_corner_v, fmove.cruise_v)
+                if max_corner_v >= cruise_v:
+                    break
+                sum_t -= fmove.accel_t + fmove.cruise_t + fmove.decel_t
+                if sum_t <= 0.:
+                    break
+            else:
+                if lazy:
+                    return i
+            move.extrude_max_corner_v = max_corner_v
+        return flush_count
     def move(self, move_time, move):
         if self.need_motor_enable:
             self.stepper.motor_enable(move_time, 1)
@@ -108,28 +113,20 @@ class PrinterExtruder:
         if (axis_d >= 0. and (move.axes_d[0] or move.axes_d[1])
             and self.pressure_advance):
             # Increase accel_d and start_v when accelerating
-            move_extrude_r = move.extrude_r
+            pressure_advance = self.pressure_advance * move.extrude_r
             prev_pressure_d = start_pos - move.start_pos[3]
-            if accel_t:
-                npd = move.cruise_v * move_extrude_r * self.pressure_advance
+            if accel_d:
+                npd = move.cruise_v * pressure_advance
                 extra_accel_d = npd - prev_pressure_d
                 if extra_accel_d > 0.:
                     accel_d += extra_accel_d
                     start_v += extra_accel_d / accel_t
                     prev_pressure_d += extra_accel_d
             # Update decel and retract parameters when decelerating
-            if decel_t:
-                if move.extruder_min_corner_v2:
-                    min_corner_v = math.sqrt(move.extruder_min_corner_v2)
-                    max_corner_v = math.sqrt(move.extruder_max_corner_v2)
-                    npd = max_corner_v*move_extrude_r*self.pressure_advance
-                    extra_decel_d = prev_pressure_d - npd
-                    if move.end_v > min_corner_v:
-                        extra_decel_d *= ((move.cruise_v - move.end_v)
-                                          / (move.cruise_v - min_corner_v))
-                else:
-                    npd = move.end_v * move_extrude_r * self.pressure_advance
-                    extra_decel_d = prev_pressure_d - npd
+            emcv = move.extrude_max_corner_v
+            if decel_d and emcv < move.cruise_v:
+                npd = max(emcv, move.end_v) * pressure_advance
+                extra_decel_d = prev_pressure_d - npd
                 if extra_decel_d > 0.:
                     extra_decel_v = extra_decel_d / decel_t
                     decel_v -= extra_decel_v
diff --git a/klippy/toolhead.py b/klippy/toolhead.py
index 768f7233..a189a848 100644
--- a/klippy/toolhead.py
+++ b/klippy/toolhead.py
@@ -125,7 +125,7 @@ class MoveQueue:
         for move, start_v2, cruise_v2, end_v2 in move_info[:flush_count]:
             move.set_junction(start_v2, cruise_v2, end_v2)
         # Allow extruder to do its lookahead
-        flush_count = self.extruder_lookahead(move_info, flush_count, lazy)
+        flush_count = self.extruder_lookahead(queue, flush_count, lazy)
         # Generate step times for all moves ready to be flushed
         for move in queue[:flush_count]:
             move.move()