 In 1909, trials were conducted with WF 436 to see if a solution could be found to reducing the amount of smoke produced by engines passing through the Lyttelton Tunnel.436 was briefly converted to oil-firing for this purpose, but although the tests were satisfactory, oil was at that time three times more expensive than coal, and so WF 436 was reconverted to coal firing.Eventually, the problem was solved by the electrification of the line between Christchurch and Lyttelton in 1929 when the EC class entered service.