Luxury brand Mercedes-Benz has asked struggling carmaker Renault for a French kiss to help shed its stodgy small-car image.
Mercedes yesterday admitted it is leaning on its alliance with the volume French brand to find a powerplant for its lower, sleeker, youth-oriented third-generation A-Class.
Due to hit showrooms before the European summer break before arriving Down Under early next year, the A-Class will come with a development of Renault’s 1.5-litre, four-cylinder turbodiesel in its efforts to sneak beneath the 100 grams per kilometre barrier for CO2 emissions.
While it will also launch the A-Class with a larger, proprietary diesel engine and cleaner, tech-clad petrol four-cylinder engines, it will be the Renault-derived four-cylinder engine which will power the entry-level A180 CDI, which is planned to be the biggest seller.
While Mercedes-Benz engineers insist they redesigned or swapped more than 50 parts in the 1.5-litre, inline engine, the core of the powerplant is the same engine that powers the French company’s humble Dacia – itself a sub-brand pitched beneath Renault.
“With 98 grams of CO2 per kilometre and 3.8 litres/100km, it is among the most environmentally friendly diesels in the compact car segment,” Mercedes-Benz diesel engine developer Dr Peter Lückert said of the engine, dubbed the OM607 in factory code, at this week’s technology forum in Stuttgart.
“The OM607 engine has been done in conjunction with Renault. It’s a Renault engine adapted massively to Mercedes-Benz requirements,” he admitted.
While the Renault version of the engine is now in its sixth generation and mostly sells in single-camshaft, eight-valve form, Mercedes-Benz has fitted it with an all-new 16-valve cylinder-head and a variable-vane turbocharger to produce 80kW of power.
It will also have 250Nm of torque when it mates to its six-speed manual gearbox, but Mercedes has wound that back to 260Nm when fitted with a seven-speed dual-clutch transmission.
“Like all Mercedes engines, the OM607 was required to complete the extensive engine test program involving bench-testing and endurance runs. The application effort devoted to the OM607 by Mercedes-Benz was very considerable,” Dr Lückert said.
“In a joint project team of Mercedes and Renault personnel, the engine was especially improved in NVH (noise, vibration and harshness) and drivability.
“Numerous components are specific to Mercedes-Benz, for example the OM607 has the engine mountings of the M270 petrol engine, as well as a special dual-mass flywheel,” he defended.
“The starter is also flanged onto the transmission and the alternator and the air-conditioning compressor also come from the Mercedes modular system.”
It will sit in the A-Class range alongside the OM651 1.8-litre turbodiesel four-cylinder engine that was introduced by Mercedes-Benz in 2011, with a high-performance “TopType” 2.1-litre turbo-diesel following later this year.
While the smaller 1.8-litre versions of the OM651 will be available in 80kW and 100kW forms, the 2.1-litre diesel will crunch out 125kW of power and 350Nm of torque, when mated exclusively to the seven-speed double-clutch transmission.
The petrol engine is an all-new animal, dubbed M270, which will power the A-Class in either 1.6- or 2.0-litre forms. Designed to be spun around and used longitudinally in larger, rear-drive Benzes as well (where it will be codenamed M274), the M270 will push out between 90kW and 155kW of power, depending on the model.
While not as torque-rich as the diesel variants, the base 1.6-litre petrol motor will offer 200Nm, while the 2.0-litre version can reach 350Nm.
Mercedes claims a number of breakthroughs with the engine, including the addition of new piezo injectors for its direct fuel-injection system, lowering emissions and making for a cleaner burn.
With the injector mounted in the centre of the combustion chamber, where the sparkplug normally sits, the fuel jet penetrates less deeply than with multi-hole or early piezo systems. With this generation, the piezo injector has a response time of 0.1 milliseconds and its injection is precise to within a few thousands of a millimetre.
That’s then hit with up to four sparks within a millisecond, creating plasma with a large expansion and a very clean burn.
While rivals from Audi and BMW offer twin-scroll turbochargers, Benz claims it can achieve the same results with more-humble variable-vane geometry turbos on its engines.
The 1.6-litre version also receives a variable valve lift system it calls Camtronic, which switches quickly between two different valve depths to improve its efficiency.
The A-Class family will be the first to use Benz’s new seven-speed DCT (dual-clutch transmission), which is good for up to 450Nm of torque and can handle engine speeds of up to 7250rpm.
The 86kg gearbox is 367mm long and will be offered with a featherweight (try 46kg) all-new, three-shaft manual gearbox in the A-Class. Both transmissions are also slated for future use in the C- and E-Class.