Turbo Timer purpose, by the manufacturers

Got | Apex? Forums - turbos and superchargers??: "'The A'PEX Timer is designed to keep the engine idling after the engine is shut down and the ignition key is removed. The purpose is to keep oil running through the turbo to cool down the center housing. This is particularly critical after a hard run, where the turbines can spin at over 200,000 RPM and reach temperatures as high as 900C...Extended and repetitive oil coking within the oil lines and center housing could result in clogging problems and damaged turbos.' - A'PEXi

'The turbo's bearings rely on a generous supply of clean engine oil. All oil pressure is lost when the engine isn't running. With temperatures ... at the turbine shaft [of] 300-350C, a hard, destructive varnish or 'coke' can form on the bearings or seals.' - Greddy Performance

'This permits the engine oil to circulate through the turbocharger bearing housing, drawing heat out of the bearings and impeller shaft in order to bring the temperature down to a safe level before the engine is shut down.' - HKS"