This article caught my attention from a tweet by SAE on the debut of Volvo’s new diesel engine. The main advancement described in the article is a more accurate closed-loop control system for fuel injection that includes a pressure sensor in each injector rather than just a single high-pressure rail sensor.
Fuel consumption of the new engines is reduced by 10-30% compared to units of similar output but of larger capacity, Crabb claimed. Denso engineers have stated that i-ART can improve fuel efficiency by 2%, compared with open-loop systems.
So is this a truly revolutionary improvement or another small incremental step? It is unclear from this quote, but my guess is that under certain conditions, they are improving efficiency by 2% – sometimes. So if you start with 40 mpg, this system could improve it to 40.8 mpg under certain conditions. Of course this is only a guess.
Something else that I found very interesting is that they are using ball bearings for the cam shafts. This can clearly have benefits on reducing friction, but ball bearings have always been avoided on engines due to a lack of load capacity and longevity. I wonder how they are solving this problem! Knowing Volvo, I am sure that these bearings have been tested six ways to Sunday. Interestingly enough, in our first CCI prototype we used ball bearings as main bearings because we were not overly concerned with longevity in that lab-only prototype.