E92 - TMS Aero & Bodywork Changes

By Thorney Motorsport

This month is a bit of a work in progress really as a race cars aerodynamics can only really be fine tuned and fettled whilst out on circuit (sadly we lack the £40m odd needed to run our own wind tunnel, although we do have access to one) so the initial stages of design are developed on the chassis in a static state. The very subject of aerodynamics tend to bring out the worst in people, everyone happily quotes drag coefficients, down force levels and anything else they’ve managed to learn from the internet usually losing sight of the one key feature that matters above all else – there is no one feature above all else – aerodynamics and bodywork design has to cater for so many requirements that there is no one single design that can do everything, you have to compromise.

For the GT3 project we have concentrated on three things – reduction of weight, increase cooling (engine and brakes) and enhanced aerodynamics.

First up in any race car bodywork development is the front bumper, what you do here affects the whole car so its development needs to be crucial. The E92 M3 has a relatively simple front bumper design which reflects the need to get air into the intake and to keep the gearbox cool, so for the race car development we kept the overall look similar – if it ain’t broke don’t fix it, this means the top part of the bumper is identical to the standard version only we have also extended the front down by another 85mm. In addition to the extra depth we’ve also added extra brake duct holes to aid cooling to the brakes, the standard bumper does have these underneath the bumper itself but by moving these to the front and expanding their size to 80mm means we shouldn’t have any issues with overheating brakes.

The underneath of the bumper is also completely different to the OEM one, the standard bumper is relatively flat then being attached to separate plastic under trays, with the race version we have integrated the separate under trays into one unit allowing for a flat floor under the front of the car and a rigid fixing to the cars chassis. The underside of the bumper is extended to take a splitter to maximise down force from the front, this splitter is made of plywood – they are sacrificial items on race cars.

Best thing about the whole design is that the road versions are identical so the road upgrade bumper will replicate the benefits of the race bumper.

The bonnet design was more about getting heat out of the engine and getting rid of weight, the standard bonnet weighs 8 kg’s which isn’t that bad really but the carbon fibre one weighs 800g, thats a lot of weight to save especially high up on the chassis so handling will be improved as well. At the same time we have been developing a larger airbox for the car so we increased the size of the hump by 15mm to accommodate that when it goes in (it also looks cool!)

The bootlid was another weight saving exercise, the standard item weighs 13kg, the replacement version only 600g, for all the bodywork we use single skin carbon fibre so its stiff but very light, for road car versions we use double skinned carbon fibre to give extra strength so we can use standard hinges and locking mechanisms. The CSL ‘flip’ design was a natural choice, the road cars look so much better with this design on.

Finally we come to the wing. Yes, its big, very very big, in fact its as big as we’re allowed under GT racing regulations as for coupe type cars as the M3 is a rear wing is essential to create the down force you need. We use a similar wing on the E46 M3 CSL Cup cars to great effect, we can run from 0-13 degrees of rake (the angle of the wing relative to the ground), have the ability to run a gurney flap (small strip running behind the wing – not shown in the pictures)  and its very light (2kg’s) which is important.

You’ll note a certain vagueness in my comments this month, thats because until we get the car on track we wont know how good or bad some of the bodywork modifications are, we know the bumper is good and there are few other way we can improve and the boot and bonnet are both exercises in weight and heat really but the wing will take some testing to find the right heights and angle for optimum performance – low drag/high down force. At this time we’ll also decide on an exhaust, side exit or rear, side allows the use of a full rear diffuser package but is more expensive and more difficult to make, rear will be heavier but easier but allows us to run a standard fuel tank, decisions decisions.