Of the major automakers, it seems like the one that's been the most ambivalent about diesel engines in passenger-car applications has been General Motors. Could it be this automaking giant is still haunted by the reputation of its unreliable oil-burners from nearly 30 years ago?
Other than the superb Duramax for the three-quarter and one-ton trucks, up until lately, it seems GM has been on the fence about light-duty diesels for the North American market. Then comes along the announcement of the 4.5L half-ton Duramax to be built at Tonawanda. Now, it's announced that GM is going to buy a 50 percent stake in Italian diesel engine manufacturer VM Motori.
Only a few months earlier, GM announced that VM Motori would be the supplier for diesel engines for the European-market Cadillac CTS. It was revealed the compact V-6 was rated for a healthy 250 horsepower and a stout 406 lb./ft. of torque. All this from a 2.9 liter package. Could it be GM was so impressed with the performance, refinement and output of the engine, that they decided it might be worth investigating a closer relationship with this engine manufacturer?
Honestly, other than both having pistons, connecting rods, camshafts and crankshafts, the troublesome 5.7 Oldsmobile V-8 diesel and this new V-6 couldn't be more different. Just look at the power figures. The Olds diesel (used across almost all the GM brands at the time) produced between 105 to 125 horsepower and 205-224 lb./ft. of torque. All the while needing a hulking 5.7 liters of displacement to do so. Granted, it did not utilize a turbocharger to make this output, but even still, the new VM engine has a specific output nearly 400 percent greater than the sluggish, smoky Olds V-8.
The fact is, the diesels from 20-30 years ago have nearly nothing in common with today's lineup. Whether you're looking at Mercedes, VW or any other company's early diesels, they were almost unanimously noisy, smoky, slow and unrefined. Now, the NVH levels have been subdued to the point where the average person probably couldn't even tell it was a diesel unless you told them. Meeting the impossibly strict Tier 2 Bin 5 emissions standards continues to be a hurdle, but the fact that it's even being considered rather than the engineers just throwing up their arms and saying "Impossible!" is a testament to how far diesel technology has come in the last 2-3 decades, though some engineers probably feel like exclaiming the "I" word while cursing CARB under their breath.
I, for one, want to extend a hearty congratulations to GM for making a bold step in the right direction, and a tangible commitment to the advancement of diesel technology.