When the roll-out of Ultra Low Sulfur Diesel (ULSD) began on June 1, 2006, it signaled a sea change in the diesel engine emissions environment. Before you jump to the conclusion of "it's the end of easy power mods for diesel engines," we've got some surprising observations, recommendations, and speculation from industry insiders on how we'll still be able to enhance the power output of our machines after January 1, 2007.
But first, since ULSD is a key component in reducing polluting emissions from all road-going diesels, here's a quick overview of what it is and how it'll affect your engine.
The EPA is requiring refiners and fuel importers to cut the sulfur content of highway diesel fuel 97 percent, from 500 parts per million to 15 ppm. The switch to ULSD fuel is scheduled to be complete this fall in California and by late 2007 for the rest of the nation.
According to the plan, owners of '07-and-later model year diesel-powered highway vehicles must refuel only with ULSD fuel. If you own an '06-and-earlier diesel, you can fill with ULSD or Low Sulfur Diesel fuel during the transition period. December 1, 2010, is the planned date to complete the transition, and only ULSD fuel will be available for highway use from that date forward.
For the most part, power and performance shouldn't suffer with the new fuel, but fuel economy is expected to be lower because the process that removes sulfur can reduce the energy density of the fuel. That, of course, lowers the miles per gallon. Expect about a one percent loss across the board.
The new fuel will have lubricity and stability additives mixed in at the refineries, making the fuel compatible with older engines. Those engines will have a bit more flexibility in that they can burn the new fuel as well as the earlier blends if necessary. The newer engines cannot.
How The New Regulations Impact The Diesel Power Aftermarket
ULSD allows several layers of emissions technology for diesels. Additional catalytic converters, particulate filters and aftertreatment components (that the sulfur would have destroyed) are on the way.
To find out how this will affect diesel performance, we talked to several industry sources and even had a terse conversation with the spokesman from the California Air Resource Board (CARB). Here's what we learned about the situation regarding installing aftermarket parts and tuning diesels for performance.
The OE engine manufacturers have to meet federal and state-mandated standards. These are different than for gasoline vehicles but include many of same elements. The difference between diesel and gas engine emissions standard is mainly found in the control of particulates and nitrogen oxides. Unburned hydrocarbons, carbon monoxide, and carbon dioxide are close to the same as gas spark-ignition engines.
In a high-pressure EGR system,...
In a high-pressure EGR system, the exhaust gas is run through a heat exchanger to cool it and then it's introduced on the boosted side of the intake. The pressure of the exhaust pulse before the turbine is used to introduce it into the air stream.
What Makes Modification Emissions Legal?
As most readers are probably aware, the aftermarket has worked with CARB to design an approval process for California street-legal, emissions-compliant components. If an installed component doesn't negatively affect the vehicle's emissions, it may be granted a CARB executive order. However, since 2001 there's been a disconnect in the ability of the aftermarket to get diesel performance products approved and get an executive order issued because CARB simply hasn't been awarding them.