Has anyone (West) done any wind tunnel testing on the Coupe ? Unfortunatly the tunnel at work, doesn't fit a full size car, so unless anyone has an 1/5 scale model I'm stuck.

Was wondering about putting a small splitter on the front, and carrying it on with some panelling under the front subframe,
the rear could be tricky, but I remember for a while there was the idea of divering the flow at the rear of a car out near the wheels.

Also need to look at someway of getting the underbonnet air out, at the moment there are some holes drilled in the inner wheel arch, but I'm guessing at high air pressure there and at the windscreen base.

Would a 1/4 scale model do? i'm thinking of doing one soon, r/c, powered by a Stihl saw motor.

My thoughts were :- close off as much of the underside of the front subframe as possible
radiator air exit vent Elise style

Hopefully someone (Neil ) will let me me know if my thoughts are all wrong

Is this the type of thing your talking about?

For the splitter/undertray, yes.

Was thinking of venting the radiator at the sides.

(please ignore the incorrect front end fit, ie too far forward, not relervant to my point)



If you look at this picture you can see the problem of front end lift at speed. Look at the (standard) lower leading edge of the front end, now look at the lower leading edge of the side sill, notice the hight difference?.

As speed builds, the air flowing under the front lower lip hits the front of the floor (the same height as the side sill height) creating high pressure, which as your speed builds further starts to lift the front of the car off the ground .

(scary at speeds over 115mph, and at 125mph a 1/4 turn giving no change of direction )

(suck eggs and all that, sorry chaps!).

If you want to test prove this quickly (as I did) I just quickly trial fitted this drop down from the front lip, creating a lower front so less air goes uder the front in the first place.

A splitter and udertray is templated and just needs laying up,and fitting. The rear has also been templated but I have no rear linkage in the way, as most of you have (not really relervant to most) but there is no reason that it can't be done, as the Cox was looked at previously. All that is needed is to create a shroud on your intended udertray that the underslung linkage can operate in.

Air exits have been covered before in anoter thread (I think it was Pantera's question) the simple way is, mark out the front end where you want the exit to be cut a "U" shape into your frontend(Oo err) place a weight on the bottom and either leave out in the hot sun for a few days (if you live somewhere hot and sunny ) or just gently warm the area at the top . Next just fill in the side area which is now open to the underside of your front end with a triangular section of whichever material you wish alley/glass/carbon ect. Da da one front air exit.

Alternatively widen the whole cars track and body, except the cockpit area by about 8 inches, then you can have air exits like the Coupe above, and duct the air out the sides.

Or just have air exits (sloted mesh vents) at the trailing edge of the front end by the front clips and use ducting (my favourite is BQ's alloy tumble dryer ducting as it is formable and about £7 for 2 meters ) and fix between the high pressure araes and your chosen exit

Side vent Ferrari F40 style.



Or Vauxhall VXR8 side vent.

What scrapyard do you go to !!!

I was thinking more on the lines of Range Rover




I was going to have a look at the local scoopermarket as well

Got a couple of spare mintes for a quick reply, I have not tested a Model of a GTM, I did start doing a CFD model but have not picked it back up in over 4 years as my computer was struggling.

Any ways

Aero and suspension setup etc have a huge effect on how the car feels at speed. When I first started in the world of Coupes, I use to run a very flat chassis, this caused stability problems at speed, putting the car 1 inch nose down over the length of the sill improved this imensly, also toe settings have a huge effect on how the car feels front and rear even in a straight line, along with tire pressures.

The front end of a Coupe does produce some downforce, but to make use of it the front bracketry holding the front on needs some beefing up. I have seen the evidance of flexing in mine and have even cracked the brackets a while back. .

At the moment my car does not have any additional aero devices, just the rake on the chassis which and even with throwing it up the drag strip at silly speeds regularly seeing 120+ this year it is still quite compossed.

Plans myself are a Flat undertray on the front I use to run a simple one years ago but never refitted it as I wanted to improve, with a huge tray simular in style to dermows above.

A Diffuser is being planned and a the moment is looking to be two tunnels starting from the seat pans.

In regards to letting air out from the front I too am planning how to address this the elise way is the mose efficient aero wise and gives downforce, another good way is sideways much like a dtm car exiting behind the front wheels.

West

Thats spot on from all the research ive done going down the same route as you

rule of thumb for a front splitter if you dont have a wind tunnel is you cannot go wrong with a flat horizontal one

I am Guilty of having spent a few years in a Wind tunnel Also have done a little consultancy on a couple of cars on the side. Plus a bit of research Best book for a general over sight/direction is Race Car Aerodynamics By Jospeph Katz.

West