Test Chamber 1
Player 1: A simple introduction to Tour Funnels: simply place a portal on the ceiling panel above the Tour Funnel, then lean over the edge to the right and trigger a second portal on the right panel.
Player 2: Drop down into the new funnel ahead of Player 1 and place a portal on the wall in front of you, as well as on the only protruding panel above and to your left. This will teleport both of you to the red button on the wall. Once you get here, stay put!
Player 1: Drop down to the temporarily extended floor below you and turn left to face the panel. Aim the funnel so it leads you straight through the doors to the exit! If you get stuck, duck to get through the door.
Player 2: Drop down into the Tour Funnel below and follow Player 1 to the right to the exit.
Test Chamber 2
Player 2: Drop down to the red button on the ground and face the wall to your left (where a row of wall tiles "staircase" up to the ceiling). Place your first portal strike in the middle of the upper-right set of tiles so it points directly across from the blue force field.
Now place your second portal on the horizontal tile where the excursion funnel currently runs to your right (this will create a funnel that will extend directly past the force field).
Player 1: Stand on the nearby Arial Faith plate, and you'll enter a vortex that will transport you to a separate section of the chamber. Once you've safely crossed over (using the button), jump down.
Player 2: When Player 1 is ready and waiting near the button, replace the portal on the far wall so it's positioned on the vertical rectangular panel facing Player 1. Make sure it's oriented so the vortex passes directly under the chute that drops the item needed to complete the challenge.
Player 1: Once the funnel is correctly positioned under the chute, press the red button to cause the cargo to fall into the funnel and merrily move to the panel at the other end. Jump back down to the first floor and stand near (but not on) the red button.
Player 2: Stand on the red button, the panels will activate and Player 1 will be able to perform the next step.
Player 1: Zoom in and shoot your first portal where the ball hits the wall, then run to the far left side of the room (towards the exit) and look up at the red laser beam high above. Opposite is a white vertical panel. Place a second portal here. This will allow the sphere to pass through where it will stop at the beam, opening the door to the exit!
Test Chamber 3
Player 1: Upon entering the main room, look for the beginning of the excursion funnel in the upper left corner of the room. Place a portal on the horizontal panel hanging above it, then look to the right and on the ground (near the stairs). There is another horizontal panel here that you need to place another portal on. This will create a funnel that reaches up to the ceiling.
Player 2: Step into the excursion funnel that rises to the ceiling and stand still to reach the roof. Now find the corner wall panel in the middle of the wall (near the excursion funnel generator). Place a portal here to prepare for the next step.
Player 1: Stand on the red button on the floor, and this will lower a vertical barrier from the roof above. Now look at the left wall, and you should notice a single vertical panel protruding from the wall. Launch your Exit Portal here (so that the excursion funnel now runs horizontally from left to right across the room). This, in turn, will cause Player 2 to fall like a stone.
Player 2: You need to react quickly as soon as you start falling, so when Player 1 removes the portal from under you, aim directly at the panel below and launch your Entry Portal here. This will cause you to fly off the inclined panel, touch the lowered barrier, and fall into the funnel, which will transport you to the platform at the exit. Now grab the patiently waiting Companion Cube, drop down to the lower level, and make your way to the red button on the floor where you need to deploy the cube.
Player 1: Once the Cube is in place, reset the exit portal so that the funnel once again extends from the horizontal panel on the ground (allowing you to jump and "float" to the ceiling). Then, have Player 2 join you so that you both end up in the same excursion funnel at the same time. When you're both ready, look back at the wall in front of you and place the portal on the vertical panel (creating a horizontal funnel moving towards the exit again). This will immediately cause you both to fall to the ground.
Player 2: Once you both fall down, very quickly place the entrance portal below you, allowing you both to hit the barrier, fall into the funnel, and be transported to the exit!
Test Chamber 4
Player 1: Upon entering the main test chamber, look to the left and place your first portal on the wall where the excursion funnel leads. Now look where the Arial Faith Plate is on the ground, turn around, and look up. You should notice a row of shooting tiles. Place your exit portal there so that when you step on the ramp, you'll land in the vortex, carrying you across the chasm.
Player 2: Jump onto the Faith Plate immediately behind Player 1 and shoot the first portal at the wall where the vortex you're in ends, then look up and to the left to see a wall covered in rectangular panels. Aim your shot so the exit vortex continues toward the ledge above you.
Player 1: Jump down to the ledge, and once Player 2 has safely joined you here, reposition the excursion funnel on the left side of the wall (so that it passes directly under the item chute on the ceiling). Go forward and press the red button now, and the Displacement Cube will fall into the funnel and be transported directly to both of you.
Player 2: Place a portal on the rectangular panel located here (where the red laser beam is), position the Displacement Cube so that the laser beam is aimed directly at the middle of the wall, and now you need to wait for Player 1 to finish crossing the chamber.
Player 1: Jump onto the ramp below, and when you land on the other side, look up and to the right to see a rectangular section of panels. Trigger the portal so that the funnel passes along the right wall. Stand on the nearby Arial Faith Plate (sending yourself back across the chasm) and simply jump down into the vortex below until you reach the exit on the other side.
Player 2: Simply follow Player 1 and make your way to the exit through the excursion vortex. When you reach the exit, find the square panel to the right and place an Exit Portal there so that the laser beam passes through the beam receiver on the wall, raising a ladder that will lead both of you to the exit!
Test Chamber 5
Player 1: This test chamber is relatively short, but it introduces you to a new aspect of changing the direction/flow of the excursion vortex. So, to start, create a portal on the square panel located above and to your left from the entrance (where the vortex enters).
Now move forward a little and place your second portal on the square wall tiles to the right. This, in turn, will create a path across the bottomless pit. Now stand on the Faith Plate to jump into the vortex. Once you reach the other side, pick up the Companion Cube hiding in the corner.
Player 2: Once Player 1 picks up the Cube, stand on the large red switch on the floor and you will both notice that the funnel has changed to orange (meaning the flow in the funnel has reversed).
Player 1: Jump back into the excursion funnel (keeping a firm grip on the Cube) and just enjoy the ride, making your way through the portals to the beginning of the excursion funnel itself.
Player 2: Once Player 1 reaches the excursion funnel device, stand up from the switch and look up and directly behind you—to your right—at the square panel. You want the exit portal to be here, as it will direct Player 1 to the square panel.
Player 1: When you approach the barrier with the square opening (only large enough for the Cube), release the Companion Cube and simply exit the funnel onto the ground below. The cube will automatically find its way to the square switch, in turn opening the exit for both of you.
Test Chamber 6
Player 1: Luckily, this is another short chamber, so start by shooting a portal at the square panel on the left wall (facing the square force field) and another portal on the ceiling where the excursion funnel stops. This will create a funnel that will stretch the entire length of the chasm below.
Player 2: Jump into the funnel that Player 1 kindly created and immediately shoot a portal at the panel directly in front of you at the end of the funnel. As you approach the middle of the room, look to the right and quickly create a portal on this wall. Now move to the middle funnel and, once you're high enough, simply jump down the horizontal funnel leading to the exit. There's a red button on the ledge; approach it.
Player 1: Now for the daring shenanigans... enter the first portal you created on the wall and reappear floating downwards (even though you'll swear you're traveling upwards) to the start of the excursion funnel itself. Have Player 2 step away from the switch and you'll float upwards. Now just find the horizontal funnel leading to the exit, enter it, and proceed to the next test chamber!
Test Chamber 7
Player 1: Once you trigger the last chamber, turn right and continue through the force field, look at the panel (top, above the red button) and set your first portal here. Lean forward and slightly to the right to see the vertical panel closest to the back of the room. Get your second portal and stand on the red button next to you to trigger the excursion funnel (it will also appear in the center of the room).
Player 2: Once the portal passes through the middle section of the chamber, stand on the plate to catapult to the other side. Once here, activate your first portal on the second vertical panel in the center of the room, then the next portal on the horizontal floor tile to the right of the panel you just placed the last portal on.
This will create a vortex that will move vertically toward the exit. Now stand on the nearby Faith Plate, and as you ascend the vortex, the force field above you will cut you off, causing you to fall.
Have Player 1 stand on the red button, causing the vortex to begin moving in reverse. Once the beam turns orange, jump into the beam and notice another platform off to the side, directly ahead. Exit the beam onto this platform with the red button.
Player 1: Return to the main part of the chamber and look at the far wall at the other end; there will now be an accessible area where you can place a portal. Now look to the left, and where Player 2 had the vertical vortex, place an exit portal on the same horizontal panel. Stand on the Arial Faith Plate and find yourself floating in a force field above you.
Once you're on the upper level, drop down the ledge and go to the upper left corner of the area where you'll see the Excursion Funnel device below. Place a portal back on the wall where the funnel hits, then look at the ledge that overlooks the main area. Place the portal back on the vertical panel next to Player 2 (to create a funnel leading back to the ledge below the force field). Once there, place an exit portal underneath it so the funnel carries the player up to the exit.
Test Chamber 8
Player 2: Walk to the edge of the metal ledge and look at the wall to the left (where the Excursion Funnel hits). You want to have the first portal at the point where the funnel hits, then the second on the panel to the left - this will create a funnel leading to an obstacle course riddled with spikes.
Player 1: Jump into the funnel and, after passing through the force field, place a portal on the wall in front of you, then on the panel on the floor. Once you reach the top, you must maintain constant communication to complete the rest of the course (so this is where you both should preferably have access to voice communication).
Player 2: You need to be constantly ready to react to Player 1's situation by standing up or turning off the red button on the floor, this will redirect the funnel flow (to make your life a little easier, zoom in with the portal to keep a close eye on your teammate).
Player 1: Activate the portal on the panel directly across from you, then have your teammate stand on the red button, which will pull you to the other side of the spikes. When you reach the end, look up to see another panel you need to launch your portal into. Have your friend step away from the button so you can begin descending toward the spikes below. You should spot a panel halfway down, so pull out the funnel from there.
Player 2: You'll need to be really quick for the next part of the spike course, as there's a circular panel of spikes that will continue to descend from the ceiling, trying to crush your teammate. Step away from the button before your friend gets too close to the crusher (if you think they're too close, step on the button to pull them back a little). Ideally, you want them to press into the spike panel when it's fully extended, as they'll just fly past when it retracts back toward the ceiling.
Player 1: Next time, you'll find yourself in another vertical section of the track, where halfway from left to right there's another spike crusher. Create a portal underneath you to ascend, and if you think you'll encounter spikes as you ascend, have Player 2 step on the button to lower you a bit. Once you've passed the trap, look straight ahead at the arrows pointing to the panel in the distance.
Player 1: Quickly place a portal hopper on the wall and have Player 2 step on the red button again. As you approach the platform below, exit the excursion hopper and look over the edge where you should see a turret guarding a Companion Cube. Jump down and to the left of the turret (which will make you much harder to spot in time), grab the Cube, and use it to knock over the turret.
Player 1: Momentarily lower the Cube and look straight up at the ceiling, place the hopper there, and have your buddy step on the button again. This will pull you up to the ceiling, straight through the spike pit. Just before you go through the next portal in front of you, exit the hopper onto the ledge on the left. Player 1: Have your friend walk to the edge of the platform above and pick up their Companion Cube; while they're aiming down, you should jump up and release the cube, and Player 2 will grab it.
Player 2: Place the Cube for a moment and look over the ledge in front of you, placing a vortex exit portal on the single square panel on the floor, creating an excursion vortex that extends to the ceiling in front of you. Player 1: Once your partner carrying the Cube reaches the top, place a portal on the inclined panel to the left, then aim it at the ground panel directly below Player 2. Fire a second portal, and your partner will drop down and pick up the Cube directly across from the exit.
Player 1: Now place a portal on the wall to your left (where the main vortex enters), and this will create a vortex extending upward from the ground. Jump into the vortex and just sit still until you reach the ceiling. Now fire a portal at the inclined panel below you as you fall down. The speed will carry you to the exit, where Player 2 should have already placed the Cube on the switch, raising the stairwell to the exit.
Test Chamber 9
Player 1: As soon as you land, turn left and create a portal on the thin panel where the vertical light bridge meets. Find an identical thin wall panel to your right. Create your second portal here, extending the light bridge and blocking the turrets hidden on the right side.
Player 2: Follow Player 1 around the room, but halfway through, turn left, look up, and shoot the portal on the tile where the excursion funnel meets. Now both of you need to turn to the left corner and look for the exit portal on the panel.
Player 1: You both need to jump into the funnel, and you'll be transported across a chasm with spikes all around and a conveyor belt of endless turrets directly below you. So, as you pass through the metal spikes, look down at the conveyor belt and directly under the left metal beam where there's a thin rectangular panel. Create a light bridge here so it will instantly protect you both from the turrets.
Player 2: Once you two reach the wall, look back and see a shooting range below. Launch your vortex from here so it carries you to the force field in the distance.
Player 1: There's a second small rectangular panel right after the first one. If you shoot it, it will provide more cover from the turrets as you approach the force field. Once you both hit it, you'll fall to the platform below and proceed to the second part of this test.
Part 2
Player 1: There's even more tomfoolery with the light bridges, so open a portal on the bridge wall, then look up and to the left where the three towers are. There's a conveniently placed panel right in sight, so place a light bridge to protect both of you.
Player 2: Your job is to control the excursion funnel, so get a portal on the funnel and then on the checkered floor tile near the corner. Now you need to have Player 1 jump into the vertical funnel first, and then you need to follow him.
Player 1: As you climb the funnel, keep your eyes open for viable panels to shoot your portal at. There will be plenty of turrets hidden in small crevices on the way up; shooting portals at the walls will create protective light barriers.
Player 2: Once you reach the top, step off onto the platform (near another vertical funnel) and look for yellow tiles on the wall to your right in the distance. The wall panel is large enough to shoot, so place a Vortex Portal here.
Now jump into the nearby vertical vortex (along with your metal buddy), and you'll be transported to the platform. Once you're safely dropped, aim upward and place a Vortex Portal on the wall here. Climb the ladder with Player 1, jump into the vortex, and then jump out at the end onto another platform.
Part 3
Player 1: The first thing to do here is go straight ahead, look through the broken panels at the vertical excursion funnel to your left. Place a portal here and on the panel located slightly to the left.
Player 2: Your goal is to take control of the light bridge, so look through the broken panels and look down to see the light bridge (zooming in will probably help). Once you reach your goal, run around the corner and look for turrets hidden on the left (just past the ledge). Block them here with a light jumper on the panel.
Both players: The two of you need to jump into the excursion funnel and ride it to the wall at the end. Player 2 should place a light jumper on the wall next to where the turrets are coming from (creating a barrier that will knock them off the conveyor belt).
Player 1 now needs to find a small square room with a broken roof located down below you. If you zoom in, a panel will appear where you can place a portal, so do so. You'll both fall, and while you're being carried, have Player 2 find a thin rectangular panel just past the metal beam.
They can place a light bridge here to prevent the turret stream from hitting you. Once you reach the end, jump into the office and turn right. When you enter, the optical disc you need will be on the table in the back. Now simply insert it as usual to complete Course 4!
Portal 2: Co-op Walkthrough:
Course 4: Excursion Funnels
Source: gamerguides.com