• improvements in the engine efficiency ratio by as much as approximately 8.5%;

• decreased fuel consumption (in liters) by up to approximately 4%;

• reduced hydrocarbon (HC) and carbon monoxide (CO) emissions by up to approximately 70%;

• reduced particulate matter (PM) emissions by up to approximately 50%; and

• the ability to reduce nitrogen oxides (NO_x) by up to approximately 30%.

On a non-optimized basis (i.e., a straight drop-in of renewable diesel for conventional sulfur-free diesel), other studies and trials have shown that using renewable diesel results in:

• 33% lower levels of fine particulates (and a smaller number of particulates in general);

• 9% less NO_x;

• 30% less HC;

• 24% lower CO; and

• reduced levels of polyaromatic hydrocarbons (PAHs).

The FEV results are based on a comparison between figures from the use of the engine optimized for Neste MY Renewable diesel and the use of conventional fossil diesel in the same engine, optimized for typical European EN 590 fossil diesel operation at Euro 6 emission level. The emission measurements were carried out before the catalytic converter and diesel particulate filter (DPF).

The results are dependent on the chosen engine, and the improvements may not all be achieved simultaneously. The listed figures only apply to Neste MY Renewable Diesel, a paraffinic fuel fulfilling EN 15940 standard specifications. Similar figures could be expected from the engine optimization for other HVO-type renewable diesels, but cannot be generalized to conventional biodiesels.

Engine optimization for HVO-type low-carbon fuels provides engine manufacturers an additional tool to improve efficiency and realize tailpipe emission compliance under real driving conditions, such as required in the Euro 6 standard valid in Europe.

—Markku Honkanen, Head of Technical Services at Neste

The study explored the potential to lower fuel consumption without compromising engine performance or increasing the noise level or emissions of nitrogen oxides (NO_x limit of 80 mg/km is set in the Euro 6 emission standard) when compared to an engine optimized for a conventional fossil diesel. Optimizing the engine for Neste MY Renewable Diesel reduced fuel consumption and nitrogen oxides emissions without affecting the high performance or low noise levels required for premium engines.

Different engine construction components and engine control parameters were tested to identify optimal engine parameters for Neste’s renewable diesel. In addition to engine testing, the results were finally verified through carrying out measurements in an actual vehicle in a laboratory setup simulating real life conditions and certification test procedures. The best results were reached by modifying only the engine control parameters, such as fuel injection control (timing, injection pressure and volume), the air volume, and the exhaust gas recirculation volume and strategy.

Neste is in the process of publishing the report in a series of technical papers in peer reviewed publications, said Markku Honkanen, Head of Technical Services at the company.