The BMW 320si WTCC A New Advertisement For BMW Customer Sport BMW has created a brand new car for the 2006 World Touring Car Championship: the BMW 320si. The company’s latest racer was developed by BMW Motorsport in Munich and is based on the production car with which it shares its name. It took nine months to create a car capable of building on the successful history of its predecessor, the BMW 320i, and the 320si is now primed to extend BMW’s customer sport activities through this season and beyond. Private teams can purchase a BMW 320si racing kit and enter the car in any of eight race series around the world according to Super 2000 or Super Production regulations. The new car was ready for delivery to the BMW national teams in the WTCC as early as December last year. And demand from other customer teams for the sportiest member of the new BMW 3 Series family is booming. A total of 17 orders have already been received in Munich ahead of the new season. The BMW 320si WTCC has certainly earned this early vote of confidence. The standard production car which provided the outline for the racing 3 handed the engineers an excellent platform for the development of the competition model. “The development of the racing car was running only a few weeks behind that of the standard road car”, notes BMW Motorsport Director Mario Theissen. “The basic concept on which the 320si is based provides an outstanding template for a racing version.” From Sporty Road Car To The WTCC The 320si is also available for BMW customers with a particularly fine nose for motor sport in the shape of a limited-edition model, of which 2,600 will be made. A high-revving four-cylinder engine which reaches 8,000 rpm, a short rear axle ratio (4.10) and M sports suspension with 18-inch mixed tyres give the BMW 320si true sporting pedigree even in roadgoing trim. However, the 40 or so BMW Motorsport employees involved in the development of the new WTCC racing car have managed to further enhance the roadgoing model’s driving characteristics in preparation for the rarified atmosphere of the world’s premier touring car race series. The BMW 320si WTCC is longer and broader than last year’s car. “A wider car means a larger frontal area”, explains Theissen. “The immediate effect of this is to increase drag. However, this can be counteracted by improving the streamlining of the car’s form. Indeed, we’ve done a great job on the aerodynamics.” The new car is much more aerodynamically efficient than the BMW 320i and also has the benefit of a wider and firmer chassis. One challenge for the engineers was how to adapt the rear axle of the BMW 320si for race action on the track. The five-link axle has a larger track width and wheel camber than the production version. Development work with Sachs saw the creation of new rear-axle shock absorbers which allow five-way adjustment. Further optimisation was also possible on the axle carriers and some pivot points. The pedals in the 2006 car also display some new features. BMW 320si WTCC drivers will use standing pedals fixed on a plate in the footwell which can be adjusted according to the size of the driver. This has helped to further lower the car’s centre of gravity. Naturally, reductions in weight also play a significant role in the development of a racing car. The engineers shaved three kilograms off the overall weight by using a new windscreen made from the special plastic Makrolon. Safety In The Cockpit, Continuity In The Transmission The BMW 3 Series is an extremely safe car and the new 320si raises the bar yet another notch in terms of both active and passive safety. Helping it to do so are the race car elements stipulated for the racing version in the series regulations, including a steel safety cage. To this end, BMW Motorsport benefited in the development phase from its FIA certification as an analysis centre for safety cells. Additionally, the driver is protected by further components such as a safety seat, the Head and Neck Support system (HANS), crash pads in the doors and energy-absorbing foam. The BMW 320si will line up in 2006 with a five-speed H-gate transmission optimised for the race track and featuring a mechanical limited-slip differential. Integrated strain gauges in the gearshift lever trigger a power signal. This quick-shift system cuts ignition during gear changes in line with the chosen configuration, removing the need to operate a clutch. Using a sequential six-speed transmission would raise the basic weight of the vehicle to 1,170 kg (incl. driver). As it stands, the BMW 320si WTCC weighs just 1,140 kg with the driver. New developments promise success on the race track The BMW 320si WTCC sees the introduction of a CAN bus system for the first time. Taking the place of conventional relay and safety technology, the newly developed high-performance control unit POWER400 uses the system to control all the actuators in the car, such as those for the lights, windscreen wipers etc. This new feature results in significant weight savings, reduced susceptibility to faults and greater ease of use. The engineers are expecting the ECU404 engine management system, another in-house development from BMW Motorsport, to provide benefits in terms of variable shift times and engine map switches. The software and interface for this technology were also created by the experts in Munich. The body for the BMW 320si WTCC is built at BMW’s Regensburg plant. The bodyshells for the WTCC car are prepared just a stone’s throw from the assembly lines for the series-production cars. Here, again, the focus is on cutting weight to a minimum. Strengthening elements have been welded in around other areas of the car to accommodate the safety cell demanded by the race regulations. The experts from the BMW plant in Dingolfing contributed their know-how in the design of the gear teeth and the materials for the rear-axle differential. The quality assurance laboratory is also located in Dingolfing. The concept and production of the cardan shaft, meanwhile, was a joint project with BMW’s Landshut plant, where the 2,600 engines for the roadgoing models are made. A certain number of the components are subsequently used in the construction of the race engines. BMW Motorsport enjoyed active support from the series-production engineers over the course of the development process. Sessions in the wind tunnel and with the pendulum test rig to establish the vehicle’s centre of gravity and transmission test rig have provided significant assistance in transferring the BMW 320si WTCC from drawing board to race track in a matter of months. The BMW P45 Engine The BMW P45 provides the powerful heartbeat of the BMW 320si WTCC. By contrast to the BMW 320i, the new car is fitted with a two-litre four-cylinder engine. As Theissen explains: “Our rivals in the two-litre class have always used four-cylinder powerplants, and that’s made BMW’s six-cylinder something of a special case in the WTCC. Now our aim is to show that we can also play a decisive role in the championship with the four-cylinder engine.” The four-cylinder is lighter and shorter than its six-cylinder forebear and develops considerably greater torque from its maximum 8,500 rpm (as dictated by the regulations), without any reduction in output. The BMW P45 engine already delivers 275 bhp, putting it on the same performance level as its predecessor. The powerplant is mounted further back in the car, which again helps to improve the centre of gravity of the BMW 320si. Synergies In Engine Construction The engine under the bonnet of the BMW 320si is also rooted in the production car’s sporty and innovative concept. The N45 powerplant, which develops 173 bhp at 7,000 rpm in the 320si special-edition model, is the first series-produced unit to feature a carbon cylinder head cover and integral oil separator. The engine developers opted for conventional valve control with two overhead camshafts, rocker arms and four valves per cylinder in the design of their new creation. The omission of numerous moved parts allows the valve train in both the special-edition model and the race-trim car to ensure impressive rigidity and precision even at high engine speeds. Following modifications carried out by BMW Motorsport engineers, the power unit was put through its paces on the state-of-the-art test rigs at BMW’s plant in Munich. The race engine then had to prove its mettle on the chassis dynamometer, which calculates the powertrain’s mechanical power loss. The engineers used the data collected to work on further detailed improvements. Like the series-produced engine, the BMW P45 is also cast in Landshut. Its cylinder head is a completely new construction and the requisite castings are produced in Landshut’s Formula One foundry. Computer-controlled machine tools ensure that the intake and exhaust ducts and combustion chambers boast maximum precision and surface finish quality. Together with the larger valves and adapted intake and outlet flange contours, this ensures optimal fuel preparation. Special spark plugs controlled by dedicated ignition coils trigger the combustion processes. Formula One technology is also lurking below the surface of other engine components, such as the rocker arms. They are coated in a process developed specially for BMW’s Formula One engines. Technical Specifications BMW 320si WTCC 2006 Vehicle Length: 4,535 mm Width: 1,845 mm Height: approx. 1,350 mm Wheel base: 2,763 mm Vehicle weight: 1,140 kg (with driver) Tank capacity: approx. 45 litres Chassis/body: Unitary construction steel body with welded safety cell made of extremely rigid precision steel tubing; safety fuel tank bedded in a CFRP (carbon fibre-reinforced plastic) sandwich tray; pneumatic three-stamp rapid jack system Aerodynamics: front apron, rear apron, rear wings, front wings and flared rear wheel arches made of CRFP Transmission: single-disc carbon-fibre clutch operated by a hydraulic central slave cylinder; five-speed dog-type racing transmission based on the production variant; additional oil/air cooler; quick-shift system with ignition cut-off controlled by shifting force; production rear axle casing with mechanical limited-slip differential and additional oil/air cooler Front axle: double-joint strut suspension with increased wheel caster angle, enlarged track width and enhanced wheel camber compared to the production version; five-way adjustable shock absorbers; tubular stabiliser bar Rear axle: five-link axle, with enlarged track width and enhanced wheel camber compared to the production version; five-way adjustable shock absorbers; stabiliser Brake System Front: four-piston aluminium brake callipers; inner-vented grey-cast iron brake discs of 332 mm diameter, 32 mm thickness Rear: two-piston aluminium brake callipers; grey-cast iron brake discs of 291 mm diameter, 18 mm thickness Steering: Rack-and-pinion steering with electric-hydraulic power assistance Wheels: Aluminium rims, 9 x 17 inches Tyres: Yokohama race tyres, 240/610 R17 (front and rear) BMW P45 Engine Type: Four-Cylinder In-line Capacity: 1,999 cc Bore x stroke: 86 x 86 mm Compression: 11 : 1 Max. output: approx. 275 bhp at approx. 8,300 rpm Max. torque: approx. 242 Nm at approx. 7,250 rpm Max. engine speed: 8,500 rpm (as per regulations) Cylinder Block: Aluminium Cylinder Block Construction with “bed blade” lower section Crankshaft: Steel Crankshaft With Reduced Bearing Diameters Pistons: Forged Skirt Pistons Conrods: High-performance Steel Cylinder Head: Aluminium DOHC (double overhead camshaft) construction; four valves per cylinder Valve Train: Two Overhead Chain-driven Camshafts; Valve Actuation Via Rocker Arms Intake System: Single-throttle Valve (64 mm, as per regulations); air box made of CFRP with load change-optimised ram tubes Exhaust System: High-performance Header, Silencer And Catalytic Converter Fuel System: Single-cylinder Multipoint Injection With One Injection Valve Per Cylinder; Injection Pressure 5.0 Bar Lubrication: Wet Sump Lubrication With Optimised Oil Sump/Oil Suction System Cooling: Water/Air Cooler And Oil/Water Heat Exchanger Flywheel: Steel, Weight-optimised To 4 kg Fuel: Standard Fuel, Super Plus Unleaded Electrics/Electronics Engine Management: BMW Motorsport ECU404 with two high-performance microprocessors; Individual Cylinder Injection And Ignition; Pit Speed Limiter Function, Quick-shift Function; Engine Data Memory System Energy Management: Electric Energy Management And Monitoring With BMW Motorsport POWER400 control unit, networking of all sensors and actuators using a bus system Cable Harness: Weight-optimised Ignition Coil: Four High-performance Pencil Coils With Integrated Ignition Drivers Spark Plugs: NGK high-performance spark plugs Cockpit: Programmable LCD display with integrated indicators Steering Wheel: Quick-release multifunction steering wheel with integrated display control Copyright ©2000-©2006 TotalMotorSport