We often hear the phrase ‘Slow In-Fast Out’ but why do coaches like me bang on about it as the bedrock of performance driving?
By turning in slower you are able to turn tighter, this pushes your turn-in further towards the bend. As you can see from the picture accompanying this article this has the knock on effect of more of the rotation around the corner being completed by the time you reach the clipping point. This in turn means the route from the clipping point to the exit is straighter which allows you to get on the throttle earlier finally meaning you exit faster.
If you gain 5mph on the corner exit by turning in slower and later you will have the advantage of greater speed all down the next straight until you either brake for the following turn or reach near terminal velocity (its a bit more complex than that but that basic understanding will do for now).
So turning in slower and later means the next straight starts earlier which makes you faster overall.