I'm not sure I could take any advice seriously from someone with in their admitted technical ability range.

Would a foam one work better Jimbo?

Obviously

I keep my intercooler in a coolbox in the boot so I don't have that problem.

no we are not talking scoops, we are talking exhaust venting, using the high velocity air over the mid bonnet region to extract the higher pressure air from behind the wheel with a duct hose(the pressure gradient is as its max here, if you put the vents nearer the wind screen the effect could be no pressure gradient or flow.). Venting the bonnet with rearward facing NACA ducts would aid the pressure gradient across the radiator and help cooling, but reducing the rad opening area will cut drag and thats the plan here. Rearward facing ducts especially with a gurney placed mid to front bonnet can be pretty sure to have an extraction effect on the bay; we arent pushing any air in from the top! The test method with tufts would prove if the vents are effective, if not out with the gaffer tape. Also don't consider what fools in RS turbos do and raise the rear of their bonnets, because at speed the lower edge windscreen pressure will force air into the engine bay, keep the rear edge sealed.

There must be quite a strong pressure difference over the rear of the bonnet/windscreen on the coupe already, it lifts the wipers off the window at speeds over 120mph. Venting air over the rear of the bonnet may help to keep the air flowing over the back of the bonnet and over the screen, a bit like a blown flap on a plane.
This may also improve the aerodynamics of the car as the air isn't separating the shape of the car causing excess drag.

Jim not sure what you are estimating here, its is the high pressure that lifts the wipers off the screen not some venturi effect sucking them off. If you vent the bonnet here air will flow from the windscreen base into the engine bay - we don't want that. But convesely a scuttle panel 'fill in' creating a smooth transition from bonnet rear edge to say half way up the windscreen would reduce the transition and seperation like you mentioned but in a different way. Not sure about visability mind.

I was guessing it actually works the opposite way round Rich, bare with me here; air has to travel further over the top of the car than it does going underneath it, so for that air to meet at the same point at the rear of the car it has to travel faster over the top.
That higher speed air causes a low pressure over the car, that's why they start to lift at speed.

Now I was guessing the wipers lift at speed due to the low pressure being formed as the air passes from the bonnet to the windscreen.

A sure way to tell would be so selotape some cotton t the bonnet rear edge and watch what it does, same for any part of the car that you want to monitor airflow, bumper rear lip etc.
If you remove the bonnet seal at the back of the engine bay, you will either see the cotton shoot inside the bonnet under suction or flow up over the window.

@Per: Why don't you give the bearded guy in the picture a shout?
As you've bumped into mr.B himself recently you might have his contact details.
If not why don't you try his office Chris Bangle Associates in Italy.

Sure Jim that would show what you want to know, but having seen countless wind tunnel reports via McBeaths aerobytes column I can be sure that what I mention is for real. Your analogy is a little too simple, sure if the body was a continuous ark then the velocity would potentially create a drop but the change in vector from the bonnet to the windscreen is huge, which creates turbulance at the base of the screen and a high pressure zone. But some tufts would tell the story real easy, and the coupes ranked screen may just level any pressure differential - you know another way is a U tube manometer, simply get some clear cappillary tube, use fence staples to make the U shape on a board, fill the U with some water, mark it in a level position (vertical board), the short end of the U is open to atmosphere and the other end extends and is taped to the test area - in this case the scuttle panel. With a friend holding the board drive the car at speed (the long end should not be facing into the direction of travel). If the water come flying out of the short end you have greater then ATM pressure in the scuttle, if its sucked towards the scuttle then you have lower than ATM pressure there.

KTM the u tube manometer test is useful for testing behind the wheels and in the engine bay to establish pressure differentials.

the chap made a huge manometer but the plan is the same
http://www.youtube.com/watch?v=0nKaGEMLZjs

Have a look at this and some of autospeeds other articles on practical things you could do
http://autospeed.com/cms/article.html?&A=2159

SediRich is right, all cars of this basic body shape have pressure at the bottom of the windscreen. And underpressure (not sure that's the english word for it..) over the bonnet centre, if anyone's considering extra engine bay venting..



Yes, we've already had some mail conversations. Quite interesting, and he's a very laidback guy . For example I found out it's the same guy who designed the Pininfarina proposal for the Coupe (and of course also the 406 Coupe) and the E60 BMW 5-series.. Davida Archangeli. " a nice irony since I later hired him into BMW and did that super-special E60 5Series I love so much (and died in the process, the poor guy)"

this is getting very involved and interesting i have to say..its gone from taping up and possibly fashioning a splitter to some serious posts ..thats why i spend way more time than i should on the forum! ..
even if a little above my head in parts i appreciate the time and suggestions ..
i am trying to take it all in but without having time to spend learning the basics of aerodynamics in order to grasp all you are telling me i can only take in so much..so i would be grateful if we can try and come up with practical suggestions i can fabricate with my limited facilities..i am happy to spend some time testing various ideas but what would really make this attept succesful would be someone that actually knows what they are doing/talking about physically helping ..so if someone fancies getting involved inbreaking the record i am happy to cover thier expenses
..i am probably asking a lot there but i have a serious lack of time with which to fill my head with enough to understand what i am doing so in truth unless someone does it will be basic stuff from whats been mentioned so far..i already know way more than i did from the links and whats been said so can at least make a better go of it
will be glad of any more thoughts though