Quote:
Originally Posted by Big Dave
Roflwaffle posted:
“I've seen 1-2% less energy on ULSD, but not 4%, any sources?”
Big Dave sez:
That isn’’t 4% less heating value in the fuel. What that 4% refers to is the EPA’s underestimation of the loss of thermal efficiency of the engine compliant with Tier II engine requirements. Tier II and ULSD go together. As usual, the EPA has (deliberately I believe) underestimated the efficiency penalty of Tier II. 2008 model IH 6.4 (Ford) and Cummins (Dodge) 6.7 diesels are showing 10% lower MPG than the same 2007 model 6.0 IH and 5.9 Cummins engines.
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OIC! Makes sense.
Quote:
Originally Posted by Big Dave
The problem is that the improvement curves have all flattened. We have hit the asymptote. All improvements will be very, very small and witll come at very high cost. This is exactly what we are seeing with ULSD/Tier II. The promised improvement in measureable air quality will be miniscule, but the costs will be enormous. At this point, until there is a massive embrace of nuclear (zero air emissions) power, all improvements in air quality come at an unacceptable price.
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I doubt that. After looking at CARB's 2007 emissions standards for heavy duty diesels, I was surprised to see they were roughly equivalent to CARB's early 80s/late 70s emissions standards for passenger car diesels, such as IDI VWs, per horsepower*hour. Since the EPA tends to be behind CARB in terms of emissions regs, I think saying that requiring larger diesels to comply with the same emissions standards diesel car manufacturers had to comply with nearly three decades ago (in the case of semis) results in minuscule AQ improvements is a bit of a stretch. The same goes to diesel pickups since they have had relatively relaxed emissions regulations as well, but the difference isn't as pronounced.