Komo-Tec in the wind tunnel of “MIRA” in England

Started on 20.02.2017

Komo-Tec in the wind tunnel of “MIRA” in England

Serious engine development requires precise measurement methods to verify and document every single development step. That is the reason why we have purchased and installed a „Schenck“ engine test bed and a four wheel “SuperFlow“ rolling road already some years ago.

However, the optimization and measurement of aerodynamic modifications on a vehicle requires a completely different effort. Wind tunnels in which vehicles can be measured in their original size are extremely rare, since their operation is associated with a very high structural and financial expenditure.

In hardly any other vehicle discipline, presumption and fact are further apart than in aerodynamics. Therefore, we were very happy to receive the opportunity for a full test programme at the „MIRA“ wind tunnel in England in order to get down to some hard facts in more than 50 measurement cycles.

We tested different wing profiles and settings, front end, underbodies and diffusor modifications on our „Exige 460“, all with the same goal:

To determine the optimal aerodynamic configuration for our „Track“ and „Race“ packages with which the best compromise between downforce and drag can be achieved. At the same time, the aerodynamic balance front/rear should be as close to the static weight distribution as possible.

At the beginning of our measurements, the following standard vehicle data were established:

Total weight 1.140,80 kg (2.515,1 lb)
Front axle load 412,40 kg (909,2 lb)
Rear axle load 728,40 kg (1.605,9 lb)
Weight distribution (F / R) 36% / 64%
Frontal area 1,70 sqm
Drag (CD) 0,41 (without rear wing)
Airspeed in the tunnel 36 m/s
All forces and moments 160 km/h (99,42 mph)

 

The baseline run without a rear wing – as the basis of all subsequent trials – showed a small amount of positive lift at the rear and a CD of 0,41.

The subsequent measurement with the original rear wing of the “Exige Sport 350” already added a small amount of rear downforce (11.8 kg). At the same time, the CD value rose to 0.44 and thus corresponded to the standard of the “Exige Sport 350”.

The „Track“ aero package consists of the 1.350 mm wide rear wing with a specially curved profile to generate an excellent ratio between downforce and drag as well as the „Lotus Motorsport“ front splitter.

Our measurements of downforce and drag at wing were carried out at angles of 6°, 9°, 12° and 14°.

The highest aerodynamic efficiency was achieved with an angle of 12° for the rear wing:

Rear downforce: 50,2 kg (160 km/h)
Front downforce: 28,3 kg (160 km/h)
Aerodynamic Balance front/rear 36% / 64%
Static Balance is identical with 36% / 64%
Efficiency (Downforce L / Drag D) -78,5 kg / 101,4 kg = – 0,775

Required power to overcome

the aerodynamic drag 61 hp (160 km / h)

For comparison:

Drag power „Sport 350“ 55 HP (160 km/h)
Drag powerwithout rear wing 52 HP (160 km/h)

 

The forces on front and rear axles increase with the square of the speed.

Thus, the downforce on the rear axle is already 122 kg at a speed of 250 km/h.

The special Komo-Tec mounting brackets are designed to sustain this load on the rear engine cover.

In the subsequent trial of the “Race” Aero package, the maximum result on the rear axle with the “Race” wing in the 14 ° position and a 5 mm Gurney at 250 km / h achieved a downforce of 260 kg. The enormous downforce of the “Race” wing with Gurney cannot be brought into balance with the downforce on the front axle at this point.

The best compromise of all the demands placed on an Aero package for the race track was therefore achieved with the “Race” rear wing without Gurney with an angle of 14 ° and in the following configuration:

  • “Race” wing (without Gurney)
  • Front Splitter “Lotus Motorsport”
  • “Canards” front
  • Splitter Fences
  • Cover on the rear lower crossbars
  • Angle of the ground (rake) is raised by 0.25 °

 

This setting results in:

Rear downforce: 72.5 kg (160 km / h)
Front downforce: 44.2 kg (160 km / h)
Aerodynamic Balance front/rear 38% / 62%

 

Required power to overcome

the aerodynamic drag 67,3 hp (160 km / h)

 

For comparison:

Drag power “Track” 61 HP (160 km/h)
Drag power „Sport 350“ 55 HP  (160 km/h)
Drag power without rear wing 52 HP  (160 km/h)

 

Efficiency (Downforce L / Drag D) -116.7 kg / 110.4 kg = – 1.057

The measurement in the overall configuration “Track” – but with a yaw angle of 6 ° – reduced the total downforce by 8.1 kg, but shifted the aerodynamic balance slightly towards the rear axle. This effect is desired since an additional stabilization of the rear axle is welcome at high cornering speeds and large yaw angles (“drift angles”).

In addition to the huge number of measured data, we were also able to collect many interesting experiences on the complex aerodynamics of the automobile. Wool threads in numerous areas of the bodywork contributed effectively to the visualization of the airflow processes around our “Exige 460”.

Our future development focus will build on these experiences and focus on the further optimization of the vehicle front, the underbody and the diffusor.

Our future aero-developments will be build up on these findings and will focus on the further optimization of the front end, the underbody and the diffusor.

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Sorry, this entry is only available in German.


Lotus Exige