Capturing automotive data to reduce emissions
The last 15 years has seen sustained effort by the automotive industry to reduce tailpipe emissions and improve efficiency. However, while reported figures mark dramatic improvements, there have been questions about how representative the claims are.
Engine emissions are often measured in a laboratory with a new engine running over a preset drive cycle. And while this intends to reflect real-world conditions, emission values can be considerably better in the lab, than on the road.
In addition, road tests used to derive mpg and CO2 figures, have been reported in some cases as using slick tyres pumped to higher than normal pressures to minimise rolling resistance, disconnection of brakes, body panels taped up to and wing mirrors removed.
The gap is increasingly growing between quoted and real figures according to some, as carmakers have been able to refine their testing tactics. According to official figures, average emissions from cars in the European Union fell from about 180g of CO2/km to less than 150g of CO2/km between 2001 and 2011. By comparison, real-world emissions were 190g of CO2/km and fell to only about 180g of CO2/km.
It follows that real-time emission figures are likely to be given increasing priority in coming decades. To help find exactly what is being emitted from some vehicles, Millbrook Proving Ground in Bedford, has introduced a Portable Emissions Measurement System (PEMS), made by US-based Sensors Inc.
The system has been designed to gather emission data from the exhaust of a normal car as it is driven. Emission data captured during this time will be a much more accurate reflection of tailpipe emissions. The test is not meant to catch manufacturers out, but rather give its design engineers more accurate data about real-world emissions. The ultimate goal is to reduce real-world tailpipe emissions and bring them in line with quoted figures.
"Essentially, PEMs are used to test mobile source emissions for the purposes of compliance, regulation, and decision making," says Phil Stones, manager of emissions and fuel economy at Millbrook's Technology Centre. "It can reliably and consistently obtain information that may not always be possible to replicate elsewhere."
Sensors Inc produces a high speed exhaust flow meter that has a sampling rate of up to 2500Hz and four differential pressure transducers. This is packaged with a number of real-time gas analysers and data processing equipment to accurately determine and capture all sorts of emissions that meet European emissions legislation including: HC, CO, NOx, NO, NO2, O2, and CO2. The equipment can be used on a wide variety of engine sizes and fuels including petrol, diesel, liquefied petroleum gas (LPG), compressed natural gas (CNG), as well as other alternative fuels. And with vehicles becoming ever more sophisticated with hybrid and plug-in capability, the PEMs equipment also allows tests for extended periods.
The PEMS is suitable for use on vehicles ranging from small cars to trucks, buses, and military vehicles, and can be designed for on-road an off-road exhaust emissions and fuel consumption measurements.
