Monday, August 6, 2012
New petrol engines for Merc's B-Class
The prime movers in the petrol variants of the new Mercedes-Benz B-Class - launched in South Africa this week as companion pieces to the diesels that were released in March this year - are in fact two versions of the same engine, an all-new, short-stroke (83 x 73.7mm) 1595cc turbocharged transverse four, tuned for 90kW and 200Nm in the B180, and 115Kw and 250Nm in the B200.
Their fuel-injection is based on the third-generation Mercedes-Benz direct-injection with fast-acting piezo injectors running at 200 bar for as many as five injections per power stroke, introduced last year with the BlueDirect V6 and V8 engines.
It has variable timing on both camshafts, multi-spark ignition, on-demand oil and waterpumps, high compression (10.3:1) despite turbocharging, scavenging for instantaneous turbocharger response and a clever new idle-stop system.
Because there's no fuel in the intake charge, it's possible to increase valve overlap to the point where some of the intake gases are lost down the exhaust manifold before shutting the exhaust valve, which improves cylinder filling, and helps spin up the turbo, considerably reducing turbo lag.
IMPRESSIVE TURNING CIRCLE
When the engine is cold in the morning, a switchable water pump with flow-optimised ball valve ensures that no coolant flows through the engine so the combustion chambers heat up quickly.
The new 7G-DCT dual-clutch transmission is a very compact, automated three-shaft manual transmission consisting of two sub-transmissions, each with its own “wet” multi-disc clutch. Both clutching and gearshifts are done automatically and without any interruption in power flow.
At only 367mm long and 86kg installed, it's more compact and lighter than previous transmissions, giving the new B-Class an impressive turning circle for a front-wheel drive minivan of only 11 metres, and in what Mercedes claims as a first, has both an electric and a manual oil pump; the electric pump keeps the poil pressure up while the idle-stop function is activated, so the car is ready to move as soon as the engine fires again, and supplies extra oil pressure under high-temperature/heavy load conditions.
The new transmission has three modes:
ECONOMY: The transmission short-shifts automatically, keeping the revs down to reduce fuel consumption.
SPORT: Still automatic, but shift and response times are set for maximum performance.
MANUAL: The driver shifts gears by paddle shifters behind the steering wheel. Shift and response times are shorter still.
The new six-speed manual 'box also has a three-shaft layout; it was designed at the same time by the same people as the DCT and shares a lot of its components.
FOUR TRIM LEVELS
The new B-Class is available to order with four trim packages - Chrome, Sports, Exclusive and Night - and a range of optional extras.
The Chrome package is standard, with three shiny slats on the grille, chrome trims on front and rear bumpers, daytime running lights with chrome ring, a beltline trim strip in chrome, chromed load sill protector and an oval stainless-steel tailpipe trim.
Inside, the Chrome package includes matrix-style trim, airvents with nozzle ring and cross in silver chrome, chrome rings for the rotary light switch, the central operating unit and the controller on the centre console, a shift/selector lever with applications in silver shadow, and contrasting stitching on the armrests in the doors and the centre console.
The Sports package has double grille slats in brilliant silver with chrome applications, diamond-pattern air intake grilles with chromed trim on the front bumper, and more chrome on rear bumper, the daytime running lights, and beltline trim strip.
Seventeen-inch five-spoked alloys are standard, the front brake discs are perforated and the front callipers have “Mercedes-Benz” lettering. Sports suspension with selective damping and the variable power-assistance and steering ratio provide for more dynamic handling.
The seats are trimmed in Artico man-made leather with contrasting stitching; The trim has a honeycomb pattern, the air-vents' ring and cross are chromed, the high-gloss black rotary lightswitch has chromed trim, and the three-spoked, perforated leather multifunction sports steering wheel has 12 function buttons.
The leather shift/selector lever has chromed trim, the door sill panels are extruded stainless-steel and sports pedals in stainless steel with rubber studs complete the look.
The Night package comes with double grille slates in glass black with chrome trim, no chrome on the bumpers, high-gloss black beltline and roof trim strips, heat-insulating dark-tinted glass from the B pillar back, 18” light-alloy rims in five-twin-spoke design, painted black with high-sheen finish and 225/40 radials.
The Exclusive package has door centre panels in Artico man-made leather with contrasting stitching and brown silk matt burr walnut trim, a three-spoked leather steering wheel with 12 function buttons, infrared comfort locking system and electric four-way adjustable lumbar support on the heatable front seats.
B 180 R 299 600
B 200 R 319 600
B 180 CDI R 325 000
B 200 CDI R 358 000
These include bi-xenon headlamps with variable light distribution and dynamic headlamp range, adaptive high-beam assist, active light function, LED daytime running lights and headlight wipers, a swing-away trailer coupling, Front seats with memory function, automatically dimming rear-view and exterior mirrors, an electrically operated panoramic glass sunroof with tilting/sliding function, A reversing camera, activated automatically when reverse gear is engaged, and active parking assist.