For 2015, Volkswagen introduced their all-new 2.0 liter TDI EA288 series turbo-diesel engines to North American models, an engine sharing very little with the one it replaced.
Redesigned to offer more power, better fuel efficiency and up to 40% fewer emissions, the new TDI engine has a number of major changes we can see as we explore under the hood of a 2015 Golf SportWagen.
The new engine has 150 horsepower at 3500 rpm, up 10 from the EA189 series and offers 236 pound-feet of torque at 1750 rpm. Changes in how the air intake charge is cooled and routed however net better response.
Its air-to-water inter-cooler is now an integral part of the intake manifold right up front. With a separate water cooling circuit, the new design shortens the path between the turbocharger and cylinders, which ultimately reduces turbo-lag.
Also up front can be seen an easily reachable fuel filter for service intervals and the belt-driven high-pressure fuel pump is located right at the front of the engine. Packaging of the battery, air filter box and ECU as as tidy as ever.
Big changes come with the dual overhead camshafts which now have variable valve timing, each cam opening one intake and one exhaust valve per cylinder. With this arrangement, the computer can vary valve timing and even effect cylinder compression ratio on the fly.
Looking down over the rear of the engine you can see the turbocharger and catalyst after-treatment bundle right up on top, with a good deal of heat shielding to be seen. But there is a lot more underneath you can’t see from here.
Turning the engine around, you see a new and quite complex catalyst and diesel particulate filter assembly which is combined as one for better packaging but also better thermal management.
And to meet US Tier 2 emission requirements, it features both a high-pressure high-temperature and a water-cooled low-pressure exhaust gas recirculation circuit.
So there’s the normal EGR path between the exhaust and intake manifolds, but also a second path which features its own heat exchanger where gasses are cooled and recirculated through the intake cooling system.
By enabling either EGR loops depending on engine load, temperatures and speeds the system allows for a dramatic reduction in nitrogen oxides (NOx) even before the Urea injection stage of exhaust after-treatment.
Efficiencies are also achieved through the reduction of friction throughout the engine assembly by some 15% using camshaft roller bearings, increasing piston-to-wall clearance, and lower piston-ring tensioning.
In our recent test drives of 2015 Volkswagen models both with manual and DSG transmissions we have found the new engine to indeed offer quicker response with much quieter and smoother operation. Average mpg observed has been in the low to mid 40’s.
See our expanded post at DieselDig.com for additional photo gallery.
