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The challenges of flex-fuel vehicle (FFV) emissions measurements have recently come to the forefront for the emissions testing community. The proliferation of ethanol blended gasoline in fractions as high as 85% has placed a new challenge in the path of accurate measures of NMHC and NMOG emissions. Test methods need modification to cope with excess amounts of water in the exhaust, assure transfer and capture of oxygenated compounds to integrated measurement systems (impinger and cartridge measurements) and provide modal emission rates of oxygenated species. Current test methods fall short of addressing these challenges. This presentation will discuss the challenges to FFV testing, modifications made to Ford Motor Company’s Vehicle Emissions Research Laboratory test cells, and demonstrate the improvements in recovery of oxygenated species from the vehicle exhaust system for both regulatory measurements and development measurements.

Atmospheric modelers and development engineers need accurate measures of NO2 emissions from motor vehicles. Due to the oxidative reaction of oxygen with NO, these measurements (typically taken from a bag sample) can be inaccurate if care is not taken to minimize the sample residence time in the bags. This reaction occurs slowly at low NO concentrations, however, at higher NO concentrations the reaction can rapidly speed up (for example, 50 ppm NO will experience a 10% concentration reduction in 6.5 minutes). This report explores the factors contributing to this artifact for emissions test cells. Estimates of the error in NO2 emission rate measurements for several scenarios are presented. Additionally, kinetic expressions of the reaction rate are shown to be fairly accurate for our test conditions, but should not be used in general without verification of the non-existence of competing, hindering or accelerating species within the sample bag.

The performance of zeolite based, catalyzed hydrocarbon (HC) traps were evaluated with different inlet HC species and warm up profiles. Five different settings of cold–start spark timing were used each on separate FTP75 vehicle emission tests with constant neutral engine idle speed and fueling schedule. A test vehicle aftertreatment system that consisted of two converter assemblies, close-coupled and underbody, was modified by exchanging the bricks in the latter assembly with HC traps. With increasing spark retard from 9° BTDC to −17° BTDC, exhaust temperature increased, engine–out non–methane hydrocarbon (NMHC) emissions decreased, the concentration of large chain (C6+) HC species decreased and the small chain (C2–3) HC species increased. Lab flow reactor experiments showed that HC traps do not effectively manage small chain HC species with efficient adsorption or retention to conversion.

The new generation of emission analyzers, MEXA 7000 series, manufactured by Horiba Instruments, Incorporated, operate as single range instruments. The wide operational range of the new analyzers requires a new calibration/linearization tool, a new gas divider capable of providing more calibration points over a wider dynamic operational range. The operation of the new gas divider (Horiba GDC-703), based on mass flow control technology, provides 40 cut points with a minimum step size of 1/500, or 0.2%, of the calibration gas value. This paper describes the new Horiba gas divider, GDC-700 series. The evaluation proves the gas divider's viability for use in engine and vehicle emissions test laboratories. Extensive sets of data were collected to provide an evaluation of the gas divider over a wide range of operation for measurement linearity, repeatability, and accuracy.