Sweating buckets

Went to Milton Keynes today which entailed a traffic jam on the M1 in what must have been our hottest day of the year so far and pleased to find the Marcos kept cool in the engine department with no overheating issues at all thanks to the efficient radiator I had designed for me, however we were roasting inside and made for a cool shower as soon as we got home.

Having tried to find out why it seems that on a hot day whilst cruising 70ish, if you wind the windows fully up the car initially is cooler inside until the cabin warms up from the sun on the windscreen but when you wind the windows down the temperature suddenly drops by the escaping heat but then after a short while with the windows down the temperature then rises to the extent that you have to wind the windows up to reduce the temperature and then the circle begins again..

My conclusion to this is that (and I may be wrong here) the heat from the engine escapes as intended from the 4 vents on the bonnet (mantula models) near the front screen, this heat escaping the vents then hits the windscreen and then goes sideways and into the cabin via the open windows hence the rise in temperature and us sweating buckets.

1/ Has anybody else noticed this ?
2/ Why would you want a heater in a Marcos ?
3/ Why did I fit a radio, I can only hear it when stationery ?



Martyn
06/07/2013.