A turbo timer is an important part of any turbocharged engine. An engine with a turbocharger must idle for a few minutes after being driven hard in order to allow the turbocharger to cool properly. Shutting the engine off immediately after a hard drive can cause serious damage to a turbocharger, possibly even ruining it. A turbo timer will keep your engine running after you turn the key off for a few minutes to give the bearings and other heat sensitive parts in the turbo to completely cool down before it stops spinning. This greatly adds to the useful life of the bearings and the turbo as a whole unit.
