Insight into aerodynamic improvements for the S2 Lotus

Exige

BySimon Farren

Presented at US Distributor Sector 111 11th April 2009

Why can Improvements be made?Manufacturers Vehicles have to meet certain criteria for type approval:

• Approach Ramp angles• Heights above ground for lamps (Minimum ride heights)• Edge radius have to meet minimum requirements

Manufacturers also try to optimise drag to improve fuel economy or top speed figures.Vehicle Styling, practicality and packaging plays an important part in design.Cost constraints

Wind tunnel testing

S2 Exige Specs TestedThe ride heights on both cars were set to 120mm front and rear.The Frontal areas: Standard Exige = 18.30 Sq ft Modified Reverie wide arch Exige = 18.73 Sq ft

Std ExigeThis had an aftermarket exhaust fitted with above diffuser exit, and a new diffuser with no Centre exhaust hole.

Reverie modified ExigeReverie Wide Arch kit +40mm front & Rear.7.5x17” Et18 (fitted with 20mm spacers) Team dynamics front wheels with 215/40R17 Toyo T1-r tyres.9.0x18” Et25 (fitted with 20mm spacers) Team dynamics front wheels with 245/35R18 Toyo T1-r tyres.Reverie 225mm chord adjustable (plan view curved) clamshell mounted rear wing.Fitted with Reverie Wide arch Exige s2 front spoiler.Fitted with reverie bolt on front S2 Elise / Exige Canards.Simulated with New Reverie Wider S2 Elise /Exige Rear Mid Floor (Tests 7,8,9 only).Simulated with New Reverie Horizontal S2 Elise / Exige Side Sill extensions (Tests 8 & 9 only).Simulated with New Reverie wide 3 element rear diffuser , running under rear wishbones (Tests 8 & 9 only).Note regrettably this car had a stage 2 exhaust with tip exits in the centre rear diffuser tunnel.

Rear diffuser smoke flow visualization

Rear wing smoke flow visualization

Front spoiler fences / canards

Side Skirts

Key aerodynamic Improvements

Taped static pressure bubble on top of front splitterMaximised under floor areaImproved rear diffuser vanes to control air flowing in from sidesSide tunnels in diffuser working as floor under wishbonesExhaust out of diffuser so centre tunnel workingFitted efficient adjustable rear wingReduced leakage of air under floor to low pressureTuned aero balance front to rear to match CoGBetter lift / drag ratio with increased down forcePositive arch louvers (not fitted in test) Allow High pressure out

Table of coefficients

10N = 2.248 lbs

Table of aerodynamic forces

10N = 2.248 lbs

Table of aerodynamic forces

10N = 2.248 lbs

Reverie positive louvers

Reverie wide wheel arch kit

Reverie aerodynamic parts on track

Recent Customer Developed Parts

Supercharged Rst-V6 550hp Evo Rear Wing, Diffuser, Floor, Splitter