Kiwi Indy stars' wheel story

Superwheels received a letter from reader Mike Ure wanting to know about the difference between Kiwis Scott Dixon's IndyCar and Wade Cunningham's Indy Lights car.

At the recent Kentucky race meeting, Dixon and Cunningham raced in their respective IndyCar and Indy Lights vehicles.

Several aero changes and the push-to-pass button were introduced to rev up the racing. "The button" was used in the now-defunct ChampCar series and is used to increase engine power over short bursts.

The device is activated by a button on the steering wheel and adds five to 20bhp, depending on fuel mixture, and up to an additional 200 engine revs.

During a race, drivers can use the 12-second burst of extra power 20 times in total. There is a stand-down period of 10 seconds after each button press to recharge the device.

The IRL previously announced several aerodynamic options that include winglets in front of the rear tyres, side-pod extensions and wheel-backing plates and the removal of the half-inch rear wing wicker. This change improves the handling of cars while drafting others and will increase speed.

IndyCar series teams will employ three rear-wing configurations, which vary according to the track.

Indianapolis 500: Consists of a main plane with no flaps. There are no restrictions on the angle of the main plane. The single-element wing is used to trim and balance the car as it travels through the flat corners at the Indianapolis Motor Speedway.

Short ovals: Consists of the standard (-2.5 degree) main plane with a top flap. The sanctioning body-designated minimum flap angle varies according to track. The two-element wing increases down force and drag and limits speeds at venues with larger turn radii and higher banking. This configuration is used at Homestead-Miami Speedway, Twin Ring Montage, Texas Motor Speedway, Kansas Speedway, Nashville Super Speedway, Kentucky Speedway and Chicagoland Speedway.

Street circuits: Consist of the standard main plane with two vertically stacked flaps. The sanctioning body-designated minimum flap angles vary according to track. The three-element wing provides maximum down force and enhances the driver's ability to carry speed through the turns. This configuration is used at short tracks such as the Milwaukee Mile, Iowa Speedway and Richmond International Raceway. The three-element wing is also designed for street and road-course use.

INDYCAR SPECIFICATIONS

CHASSIS
Type: Open-wheel, single-seat, open-cockpit and ground-effect underbody; outboard wings front and rear.
Construction: Monocoque contains cockpit, fuel cell and front suspension; engine is stressed (integral) member of chassis, rear assembly contains bellhousing, gearbox and rear suspension members.
Materials: Carbon fibre, Kevlar and other composites.
Weight: 709kg minimum for ovals and 739kg minimum for road courses, including lubricants and coolants. Does not include fuel or driver.
Length: 490cm minimum.
Width: 200cm maximum, 190cm minimum (measured outside rim to rim).
Height: Approximately 96cm.
Wheelbase: 300cm.
Wheel Size: Front: 38cm diameter, 25cm wide; Rear: 38cm diameter, 35.5cm wide.
Tyres: Firestone Firehawk. Front diameter: 66cm maximum, 63.5 cm minimum @ 35psi; Rear diameter: 69cm maximum, 67cm minimum @ 35psi.
Gearbox: XTRAC (gears forward of rear axle) six forward gears, Mega-Line Assisted Gear Shift (paddle-shift).

Fuel Cell: Single, rupture-proof cell, 83 litres.
Manufacturers: Dallara Automobili, Italy.

ENGINE
Type: 3.5-litre V8, 32-valve dual-overhead cam (DOHC), normally aspirated (no turbocharger) four camshafts, four valves per cylinder.
Weight: Minimum dry weight is 127kg - no headers, clutch, engine control unit, spark box or filters.
RPM: 10,300 maximum (league-supplied rev limiter).
Power: Estimated 650 horsepower.
Fuel: 100 per cent fuel-grade ethanol.
Injector: Electronic.
Models: Honda Racing Indy V8.
Manufacturer: American Honda Motor Company.

INDY LIGHTS SPECIFICATIONS

CHASSIS
Type: Open-wheel, single-seat, open cockpit and ground effect underbody; outboard wings front and rear.
Construction: Monocoque contains cockpit, fuel cell and front suspension; engine is stressed (integral) member of chassis, rear assembly with gearbox and rear suspension members.
Materials: Carbon fibre and composites.
Weight: 649kg minimum, including all lubricants and coolants used, but does not include fuel or driver.
Power: 427bhp 3.5 litre V8 built by Speedway Engines - a modified engine from the Infiniti Q45 street production car.
Length: 486cm minimum.
Width: 190.5cm.
Wheelbase: 297cm.
Wheel size: 38cm diameter x 25.4 front; 38cm diameter x 35.5 rear.
Tyres: Firestone Firehawks.
Gearbox: Ricardo six forward gears, sequential shifter.
Fuel cell: single, rupture-proof cell, 95 litre.