Drewd wrote:
Other than what Sir Sam and GDE posted, I will add the following about biodiesel
• Lower fuel economy and power (10% lower for B100, 2% for B20)
• More nitrogen oxide emissions
I ran B100 (actually 99) for a short while in my CRD and TDIs. At the time, the higher cost of biodiesel purchased from a Denver Co-op and the decrease in power made it a no-brainer to stick with B20 and lower blends. However, if I could get B100 cheaper than diesel-*F*, could you sell me some of your stash?- I'd gladly put up with the decrease in power.
The "more nitrogen oxide emissions" needs to be clarified a bit. The vast majority of bio fuel studies on diesel engines show bio to output lower particulates and increased NO2 and NO3. The problem is most studies just change the fuel and do not change the engine calibration to match the fuel properties. Since bio fuel has much higher cetane ratings (55-65) it auto ignites faster than #2 diesel with cetane around 40-45. The earlier combustion leads to the higher levels of NOx emissions. If the timing was retarded a couple degrees the NOx emission drop back to the same levels of #2 diesel and still have less particulates. In the future as more diesel engines get combustion pressure sensors built in they will be able to adjust the injection timing based on the rate of cylinder pressure rise in a closed loop feedback internal to the ECM. This will help make diesels more "flex" fuel capable with less noticeable differences in engine operation.