The UK's Controlled Power Technologies (CPT), working with Austria's Technische Universitat Wien (TU Wien), has demonstrated how its SpeedStart belt-integrated starter generator (BISG) 48V mild hybrid can help reduce NOx emissions and improve fuel economy in diesel engines using the latest emission test procedures.

CPT, established in 2007 after a management buy-out of Visteon's advanced powertrain capability, has forged a reputation in the industry for delivering interesting solutions using its switched reluctance machine (SRM) technology. Among these solutions is its former VTES (variable torque enhancement system) that morped into Valeo's electric supercharger first employed on Audi's SQ7 SUV in 2016; a development made possible after Valeo purchased the technology in a GBP30m deal in 2011. 

In the latest demonstration of the benefits of its SRM technology CPT has again turned to its SpeedStart BISG which first saw the light of day in 2009 and has since been applied to the ADEPT electric prototype project led by Ricardo. 

In its work with TU Wien, CPT demonstrated that its 48V BISG system could produce a 9% reduction in NOx emissions while simultaneously improving fuel economy by 5% when applied to a premium saloon running a 3.0L V6 diesel engine. The benefits are achieved because an SRM machine can respond swiftly to fast changing and transient road conditions. The test was conducted utilising the forthcoming Worldwide Harmonised Light Vehicles Test Procedure (WLTP); the latest compliance requirement for any new cars launched onto the EU market from September 2017 onwards.

48V mild hybrid systems are expected to experience rapid growth – just-auto's QUBE service sees a mid-term (2017-2021) CAGR of 71.4% before hitting a global volume of 17.5m in 2031 – as they represent a low cost but high CO2 benefit alternative to full hybridisation and fully electrified vehicles. 

According to CPT the cost-benefits of 48V mild hybrids are amplified when using its SRM technology due to the lower PGM (platinum group metals) loading requirements on lean NOx trap (LNT) catalysts and selective catalytic reduction (SCR) in diesel engines. 

PGMs are a major cost component of exhaust aftertreatment technologies required by diesel engines to meet the stringent NOx limits imposed by the Euro 6 regulations. According to Johnson Matthey the average vehicle employs some 4-5 grams of PGM per exhaust, albeit there's a wide range beginning at 1g for microcars to 15g and over for larger vehicles. 

 "This research shows that the transport sector can further reduce air pollutants without it costing the earth," says CPT's co-founder and chief executive Nick Pascoe. "The cost competitiveness of 48V technology, compared with full hybrid and plug-in solutions, is a critical issue for the automotive industry, and gives it a breathing space while pursuing more affordable fully electric vehicles." 

That breathing space may be particularly welcome news for OEMs who are battling to balance meeting tightening global CO2 regulations while being somewhat hamstrung by the mounting cost of diesel aftertreatment and an increasing opposition to the presence of diesel-engine vehicles in urban situations. Hitherto, diesel has been a key component in the industry's toolbox for reducing fleet CO2 emissions.