The Tiger's engine had two exhaust pipes exiting the hull through holes in the rear wall. Mufflers were provided, outside the wall, to reduce engine noise; they took the form of sheet-metal cylinders.
The exhaust pipe enters the muffler near its bottom, and gases are expelled at the top. The mufflers have internal baffles [1, see 3.1.1] ; but I have no images of them.
Because the Tiger is capable of driving while submerged, a non-return valve is built into the top of each muffler as shown here. This consists of a hinged flapper about 90mm in diameter.
Normally the flapper is held open by a folding pin pushed through the hinge. The pin is on a chain. [2]
When the Tiger is configured for submersion, the pin is removed, allowing the flapper valve to fall shut, as this model shows. Exhaust gases would push it open intermittently while underwater.
Photographs show the flappers aligned on the hull in any of these three ways. I don't yet know whether these were randomly assigned or can be tied to manufacturing date. In every photograph that I have seen, one of the bolts is central at the rear of each muffler.
Such was the power of the engine that flames were emitted from the top of the mufflers. The 502nd heavy tank battalion, operating near Leningrad in the winter of 1942, found that the enemy could see these and identify the Tigers too easily. They therefore attached extension pipes of various lengths and diameters to the tops of their tanks' mufflers. One example is shown here; it had slots cut into the sides to provide a draft.
This extension pipe is a full 500mm long and was used by the 502nd on Tiger "100" and at least one other tank.
In January 1943, starting on hull 250082 [1, see 3.4.1.14] , a standard solution to this problem was built into new Tigers. Sheet-metal guards were added to the hull surrounding each muffler, so that they would not be visible when glowing in the dark. A baffle plate was added to the muffler itself to deflect the flames sideways. This diagram shows the top of a muffler; the baffle plate is supported on five tubes. Long bolts run through the tubes, terminating in the M12 threaded holes in the muffler. Thus, the baffle plate could be backfitted to existing Tigers.
In September 1943, the submersion ability of the Tiger was dropped. Mufflers were now built without the flapper valve, as this model shows.
Of all the Tiger hulls surviving in museums, only the Sturmtiger in Kubinka still has original flapper valves.
[1] Germany's Tiger Tanks, volume 1 : DW to Tiger 1
[2] "Auspuffanlage (Versuch)" Henschel drawing of possible exhaust muffler