I had a hard time explaining to you what a turbo timer is so I just copied this of a site. I couldn’t have said it better lol.
A turbo timer is a device that allows your turbocharged car to idle for a specified period of time before shutting the engine off.
Why use a Turbo Timer?
The shafts on most turbochargers spin in excess of 50,000 RPM and generate lots of heat. To keep your turbocharger's heat under control, most are cooled by circulating oil or water (coolant) around the shaft. The turbocharger's shaft is free to rotate at will and there is no way to stop the shaft from spinning after shutting the engine off. To dissipate and stabilize the heat in the turbocharger, most manufacturers recommend that a car be idled for a period of time after moderate to hard driving to allow the oil/water to take heat out of the turbocharger.
Failure to reduce the temperature of the turbo could result in the oil around the shaft "coking". Coking is basically the baking of oil, turning it into a hard substance that could plug your oil lines and cause oil "starvation", preventing proper cooling of your turbocharger and reducing it's operating lifespan.
You don’t need one because I know enough guys that have turbo cars and don’t have a turbo car. But it is pretty cool and I would recommend it. It’s also really cool when you just walk out of your car and it turns off by itself after a while. Lol