How does DD15's turbo compounding work?
I see that Detroit Diesel is now offering a 2013 DD15 without turbo compounding, and they say that this is the most fuel efficient engine. Does that not indicate that Turbo Compounding (TC) was a mistake? After all, if you are using exhuast pressure/flow to spin the turbo in the first place, does that not take just as much power from the engine to spin the turbo in the first place.... compared to the power you "get back" from TC? Keep in mind that with DPF behind the turbo, there is little desired heat exchange to help spin the turbo for "free" (you do not want to lose exhaust temps, or the DPF will not stay clean without a (fuel powered) regen. I'd love it if Kevin would interview a Detroit engineer about these exact questions. Why even continue to offer DD15 with TC if it is not as efficient as the new model without!!
from the detroit web site
Designed for in-town, construction and less-than-load (LTL),
then noteing what it's designed for you get the next statement.
the Detroit DD13 stands out for its best-in-class fuel-economy,
''i have yet to see the detroit website list the turbo compounding as an option. dealers have told me it's because the dd13 is designed to have a PTO and that gets in the way of the turbo compounder.
if you hall mainly light loads the dd13 would get better fuel economy than the bigger engines.''