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My bonnets are being painted at the moment and I took the opportunity to sort out the problem of hot air from the engine bay entering the ventilation system. Not a problem in winter but particularly annoying in summer. Our car is fitted with aircon and the hot air in summer also overides the aircon to a fair degree.

Whilst at the factory I bought some new rubber foam trim for the air intake plus 2 extra pieces. I would be embarrassed to tell how much they cost!!!

Anyway the two parallel central pieces will block the air that normally enters through the gap at the front of the airbox. They are not fixed at the moment because I want to make sure the hinge return does not foul them. Also I have a sheet of black foldable plastic that will be formed and used to cover the inlet between the two pieces.

The two boxes thus formed will sit under the intake louvres on both sides of the hinge and, hopefully, seal agaist the underside of the bonnets.

All the air to the heater and A/C enters through the same point, the letter box slot in the top of the heater.

If the foam doesn't properly seal the gap between bonnet and heater box hot air enters...more than usual.

The S5s have a modern re-circulating air heater box...so the heating and A/C work like a cheap modern econo-box, thather than a 1960s car....

I don't think blocking the airbox would present any problems but of course you would not get any ventilation then.

Regarding weak aircon: I have covered the tubes with insulating material in an effort to improve things. I have also tried to block the gap in the front of the airbox but it was not a good solution. This will work better I think and I am just waiting for the bonnets to come back from the painter to complete the "boxes".

On the Plus 4 the alternator is on the left and the aircon compressor is on the right. The tube for the aircon then passes behind the radiator, in the hot air flow, and then along the side of the engine bay. The return tube to the aircon radiator is also too long and loops around behind and above the radiator.

A better solution would have been to fit the alternator to the right hand side of the engine and the aircon on the left. This would give a much shorter run for the cold gas and avoid the section that runs in the hot air behind the radiator. If ever I have to do major work on the engine or change the engine I would make this mod.