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The Hydrogen-Balance equation makes it possible to calculate the fuel economy or fuel consumption of hydrogen powered vehicles simply by analyzing exhaust emissions. While the benefits of such a method are apparent, it is important to discuss possible influencing factors that may decrease Hydrogen-Balance accuracy. Measuring vehicle exhaust emissions is done with a CVS (Constant Volume Sampling) system. While the CVS system has proven itself both robust and precise over the years, utilizing it for hydrogen applications requires extra caution to retain measurement accuracy. Consideration should be given to all testing equipment, as well as the vehicle being tested. Certain environmental factors may also play a role not just in Hydrogen-Balance accuracy, but as also in other low emission testing accuracy.

Although hydrogen ICE engines have existed in one sort or another for many years, the testing of fuel consumption by way of exhaust emissions is not yet a proven method. The current consumption method for gasoline- and diesel-fueled vehicles is called the Carbon-Balance method, and it works by testing the vehicle exhaust for all carbon-containing components. Through conservation of mass, the carbon that comes out as exhaust must have gone in as fuel. Just like the Carbon-Balance method for gas and diesel engines, the new Hydrogen-Balance equation works on the principle that what goes into the engine must come out as exhaust components. This allows for fuel consumption measurements without direct contact with the fuel. This means increased accuracy and simplicity. This new method requires some modifications to the testing procedures and CVS (Constant Volume Sampling) system.

New Federal and California Regulations present some new challenges for emission testing as low emission variability and different test cell environments through SFTP. One approach to achieve these challenges could be replacing the human driver by a robot driving system. To make a great step forward in the improvement of such robot systems, the German automotive technology research association (FAT) initialized an investigation program in cooperation with three different suppliers. The work was done and reported by the Department of Internal Combustion Engines at the Darmstadt University of Technology. This report summarizes the comparison of the driving style of the human driver to three automatic driving systems from those major manufacturers and some basic optimization work.

In the environmentally conscious world we live in, auto manufacturers are under extreme pressure to reduce tailpipe emissions from cars and trucks. The manufacturers have responded by creating clean-burning engines and exhaust treatments that mainly produce CO2 and water vapor along with trace emissions of pollutants such as CO, THC, NOx, and CH4. The trace emissions are regulated by law, and testing must be performed to show that they are below a certain level for the vehicle to be classified as road legal. Modern engine and pollution control technology has moved so quickly toward zero pollutant emissions that the testing technology is no longer able to accurately measure the trace levels of pollutants. Negative emission values are often measured for some pollutants, as shown by results from eight laboratories independently testing the same SULEV automobile.

This paper reports on the development and testing of a compact and mobile CVS system for the measurement of particulate matter emissions of diesel passenger cars. It consists of the same components as a conventional CVS system but needs much less space. Reducing the size of the CVS system was achieved by the optimization of the turbulent flow in the dilution tunnel by the use of an optimized mixing chamber, in which the engine exhaust gas is diluted with filtered ambient air. The measures taken to improve the turbulence in the dilution tunnel lead to the same effect as a tunnel with dimensions according to the legislative regulations. All the components of the mobile CVS system are arranged in a very compact design, so that the new system has a size of only about (1.70 x 0.80 x 2.10) m. Due to the mobility which is possible with such a design, the new system can be quickly adapted to different engine and vehicle test cells for passenger cars.