The Plus 8 has Aircon: it will be interesting to see how well it works, but as Peter says, sealing the inlet area of the heater box to keep engine bay air out is crucial.

I'm beginning to think that a raised solid edge for the heater box to within 1cm of the bonnet and sealed with a "D" rubber seal to meet the bonnet might be the answer.

The problem is you can't see or measure the gap with the bonnet open or shut. So it can only be done by trial and error using "witness chalk". Very, very tedious.

Of course a really expensive improvement is a new bonnet with the rear 4 louvres reversed, to scoop air in.



Peter,
66, 2016 Porsche Boxster S
No longer driving Tarka, the 2014 Plus 8...