The new 1.6CDTi diesel in a Zafira where it needs urea injection to meet Euro 6

The new 1.6CDTi diesel in a Zafira where it needs urea injection to meet Euro 6

It's not that long ago some of General Motors Europe's engines had a pretty poor reputation for durability as plastic cam belt pulleys failed or water pumps seized at relatively low mileages, cam belts were thrown off and engines self destructed, while the automaker, in the absence of a cast-iron, official dealer network-only service history, was often pretty unsympathetic to owners.

Designs did improve but consumers have longer memories than marketing wonks and I can't help wonder if those less than stellar days are partly behind the planned massive revamp of Opel/Vauxhall powertrains with the launch of three new engine families and 13 new engines between 2012 and 2016, renewing 80% of the line.

We've already covered the details but have now had the chance to visit Opel's tech centre in Dudenhofen, not far from company HQ on the outskirts of Frankfurt, and have a brief try of both new engines and gearboxes.

Essentially, GM is slimming down its in-line petrol engine families from seven to three in I3 and I4 configuration and categorising them into small (1.0-1.5-litre, medium (1.6 and 1.8) and large (2.0-2.5). Medium petrols and diesels are in production in Hungary this year and the small units follow in 2014.

Petrol and diesel are made on the same line in this flex plant.

The engineers are pretty proud of what they achieved with the petrol units, getting CO2 down by over 10% and torque up 30%. Noise is down about 2db and the medium engine meets Euro 6 emissions with only one close coupled catalyst. There's both 'eco' and performance versions; the eco made its debut in the new Cascada convertible at Geneva.

And forget rubber belts and disintegrating pulleys - chain drive camshafts and gears are now used.

The new CDTi diesels are new, all-alloy engines and mark the end of using ancient, 80s-designed Isuzu designs and those from the more recent alliance with Fiat that ended in 2005.

In-house design - in Torino - began with a "clean sheet" in 2008, according to chief engineer Gianmarco Boretto with the aim of class-leading power density, "right sizing" to replace the current, rather agricultural two-litre, low fuel consumption and CO2, set an NVH benchmark and meet Euro 6.

Vehicle integration and calibration was done at Russelsheim and there was some help from Warren Michigan and Millbrook in England.

Over 1,000 test engines were used and 24,000 hours of analysis work.

Boretto highlighted the clever integration of oil and vacuum pump in the oil pan, a two-step variable displacement oil pump that distributes the gooey stuff according to need (including via electronically controlled piston cooling jets) and a switchable water pump that doesn't kick in until the coolant is warm enough to need circulation.

It'll appear first in the Zafira Tourer where it also needs urea injection to meet Euro 6 though installation in lighter models like the Meriva require only a NOx trap and DPF.

Control is by an Opel developed ECU with 150 diesel-specific functions but a reduced number of sensors.

We tried it briefly; there's quite a bit of diesel 'combustion crackle' outside the car but it's much quieter inside and pretty refined with low vibration levels. The 1.6 petrol was smooth and quiet but needed plenty of stirring of one of Opel's new gearboxes to make decent progress.

But then, we did try it straight after a stonking V6 with an eight-speed auto....

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