Monty ... are your bonnet-side louvres 'ins' rather than 'outs' like mine? (Why do I have a bad feeling I might be re-opening some previous 'louvre-wars' thing from before my time here as I type that! 🙂)K
My louvres are 'Ins' on the bonnet sides, they are designed to bring air into the engine bay and create a positive pressure within the engine bay when the car is driven at speed.
My louvres on the top of the bonnet are 'Outs' so that's where the positive pressure vents, and carrying with it the hot air it's picked up on its way out.
This arrangement makes perfect sense to me given heat rises, afterall the purpose of the louvres is to evacuate heat from the engine bay, so it seems logical to have the 'Outs' at the highest point possible.
It's the basic principle of a chimney, even without airflow and the positive pressure in the engine bay created at speed, the hot air at idle when the car is stationary will still naturally rise to escape from the bonnet top out louvres.
