The Tiger's engine drew its combustion air through a large round cap on the engine compartment hatch. By August 1942 [3] , the designers had added a rectangular slit at the front of the hatch.
But the engine's air filters were deemed inadequate for the dusty air of North Africa. By October 1942, external air precleaners were provided with all new tanks. This photo shows one of the two precleaners (on the preserved Tiger in Bovington Museum).
Air was taken into pipes on top of the engine deck, and brought back to the precleaners on the outside of the rear hull plate. The clean air was then sent forward through other pipes to the existing rectangular slit in the engine hatch. The round cap on the hatch was to be closed in dusty conditions [3] .
This diagram shows a precleaner unit.
Inside each can were 9 vertical tubes arranged in a circle, with another tube in the middle [2] . They apparently extracted dust through centrifugal force. The dust accumulated in the conical bins at the bottom. In this museum vehicle the caps are missing from the bins, though they were once attached by chains.
The units were bolted, via 35mm-wide metal strips, to welded lugs on the hull. (The long support arm in the foreground has nothing to do with the air cleaners.)
The method of attachment can be seen here. The unit was tilted at 9 degrees, parallel to the hull rear plate.
The design of the filter units was simplified in March 1943. This diagram shows the new design. Only the casing seems to be changed.
The precleaner system was dropped completely from production in October 1943. But the mounting points on the hull rear plate were included on new tanks for about three more months [3] . This diagram shows the mounting points.
[1] Survey of vehicle 250122, Bovington, by David Byrden
[2] Survey of vehicle 250122, Bovington, by Hilary Louis Doyle
[3] DW to Tiger 1