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Jim Bauman
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How does DD15's turbo compounding work?

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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!!

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Chris Hileman
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Will this new engine eliminate the need for a variable geometry turbo? No more turbo actuators? No more turbo problems? I have questions too.

The new DD15 uses an asymetric turbo instead of variable geometry. I like that, at variable geometry turbos (think ISX and Volvo) are not reliable past 300,000 miles.... and very expensive to get a reman.

Jim Bauman,

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richard
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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.''

http://www.demanddetroit.com/engines/

Turbo compounding was/is only offered on DD15. It adds weight (100 lbs) and complexity, so it is not practical for local driving only, where mpg is not as important. TC actually is a slight negative on mpg when pulling light. Thats probably party why DD15 without TC is said to be more efficient overall.

Jim Bauman,

i must have transposed the 2013 into the dd15 in my mind when i saw this a the other day.

richard,

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