This seems to be a controversial subject.

The original idea of the raised bonnet was to allow air to be drawn in through the rear of the bonnet. A slight lip at the rear of the bonnet allowed this.

Now it is popular to see on various cars. Using washers to raise the bonnet means the edges of the bonnet are raised as well so the pressure difference is not their to allow air to be drawn in through the rear. Instead the theory is that hot air is expelled through this gap, sounds good in theory but i have yet to find any evidence that it works.

This gives a couple of good drawings:
http://www.driftworks.com/forum/technic ... ofile.html

There is also a basic experiment by a Honda owner who took temperature readings with bonnet raised and without over a set amount of time. He found the temperature at the inlet actually increased with the bonnet raised, theory being that hot air is now forced over the inlet where it isn't usually and heated the inlet more than usual.
There are some good pictures from some students in the US who used thermal imaging to investiagte it as well and found no advantage.

Having open throttles by the firewall means that if this theory worked and reduced bay temperature it would help me a fair amount, but it seems to make things worse.

Any one else have any experience/views on this?

Might have a little experiment.

Seen people with it, looks silly and doesnt work IMO.

it will work differently for different cars. it probably wouldent help much with yours you would be better off getting a really good cold air feed to the trumpets. raising the bonnet works in diff ways one is it can help better air flow over the car. and with some cars pulling the cold air trought engine will lower the overall temp even if the manifold gets a bit hotter will aid the cooler temp of the rad and if turbo'd also intercooler. sort of the same as bonnet vents do

Someone on Driftworks had a proper diagram, (not something that looked like it was done on paintshop!), where it actually gave different pressure points along the length of the car, his theory was that it did no good at all, other than when you're stopped, which is why some people who have dyno'd their cars have seen an increase in power.

As Diamondsink said, looks stupid too.

Alex B

Hot air is usually generated in the passenger seat. Best advice is to open a window!

Do the wool test on it. Tried it on my car and it acted as an intake (As its a high pressure area).

Shame I don't have the car any more

If it did act as an intake it would have been ideal as the throttles were facing the firewall.

From the sounds of it, its coming from the drivers seat in Kyles car!