It’s not every day I visit a company only to be told “You’ve probably come six to 12 months too early”. But then it’s not every day we get a story about a joint venture aimed at converting existing Euro 4 truck and bus engines to Euro 6 emissions standards while also improving fuel economy.
So what’s this about? British-based Controlled Power Technologies (CPT), which majors on drivetrain electrification, has joined forces with Eminox, the emissions-busting specialist, to develop just such a system. It’s based on CPT’s electric supercharger and Eminox’s SCRT (combined continuously regenerating trap and selective catalytic reduction) technology.
What’s more, this is just one of several projects harnessing CPT’s 48V electrification platform. Others include its Cobra (controlled boosting for rapid response applications) electric supercharger, Tigers (turbine integrated exhaust gas energy recovery system), and SpeedStart and SpeedTorq motor-generator torque-assist and kinetic energy recovery systems.
First things first. Why should anyone electrify powertrain ancillaries currently driven mechanically? CPT’s CEO Nick Pascoe explains that to gain engine efficiencies and cut emissions, truck and bus makers must follow the car makers to electrification. “The truck industry can’t ignore what’s happening in automotive, even if there is a time lag.” But while electrification of CVs may well mean going bigger, more powerful, it doesn’t automatically mean full electric drives. “That’s the last thing you go for,” he insists.
Which is not to say CPT isn’t involved with electric drives. The firm is lead contractor on Project Fever and is developing a 48V ultra-lightweight electrified rear axle for a hybrid city car in partnership with Ricardo, Tata Motors European Technical Centre and Provector. For CVs, however, its electrification priorities are to cut (or eliminate) parasitic losses from engine ancillaries, harvest wasted energy and provide supplementary power boost for downsized truck and bus engines.
CPT sees 48V as the future here. Why? Because you can run ancillaries more efficiently at 48V, than 12 or 24, not least due to the lower current draw. Why not go higher than 48V? “Because at 60V you hit a safety limit,” explains Pascoe. “That’s when the big orange cables appear and the costs start soaring.”
So which ancillaries are ripe for electrification? Pascoe picks out fuel and steering pumps, each of which typically requires 5—10kW. Electrification could also supplement air compressors on downsized diesels. However, you need to do more than simply swap a mechanical pump for an electric alternative, he says. You need to make it switchable, with on and off control, and ideally also regenerative.
Mark that last word. For Pascoe, electrification is in large part about recycling energy. On trucks and buses that means regenerative braking and waste heat recovery – using CPT’s Tigers. “Then you’re not only getting your electrical energy for free, but you’ve also got ways of returning energy back to the wheels,” he explains.
Consider CPT’s SpeedStart motor generator (engine side of the clutch) and SpeedTorq (driveline side) for electrically-driven transmissions and axles. As well as replacing alternators and starter motors, these can boost engine torque in launch and hill climbing. It’s about helping the engine through “maximum flame growth”, says Pascoe. “We’re reducing demand on the combustion chamber when NOx is at its worst and the chamber hottest.” The choice of drive – direct to the starter ring-gear or belt-driven – then depends on engine size and cranking cycles.
However, with motor generators and regenerative braking (typically recovering 10—12.5kW) effectively providing free energy, what is the best storage method?’ Not just batteries, replies Pascoe. A more attractive solution is supercapacitors which can capture and release large-scale electrical energy very fast. “That’s why I say come back in six to 12 months,” he laughs.
But there’s more. On the boosting front, Pascoe reiterates there’s nothing to be gained simply from swapping turbochargers for electric compressors. “Turbochargers are very good at providing pressurised air into the engine. Their problem is they can’t do it quickly.” That’s where CPT’s electric supercharger comes in. It can deliver more air, faster at low engine revs, so ensuring better combustion, performance and emissions, particularly on downsized engines.
So how will a CPT/Eminox Euro 4 to Euro 6 conversion perform? CPT engineering manager Andy Dickinson explains that its Cobra supercharger will “fill-in some of the operational holes” of existing engine turbos. It will reduce engine load, especially during launch, so allowing the fuel sweet-spot to be enlarged, particularly into the lower rev range. That, in turn, delivers the driveline efficiencies and fuel savings.
“It’s what we call part-load assistance. We’re providing air all the time, which means the engine doesn’t have to pump so hard,” he says. And he adds that, since accelerating Cobra to 50,000rpm takes just 0.5 seconds, air is delivered super-fast on demand. Meanwhile, better combustion means lower emissions, especially particulates – which are then tackled downstream by Eminox’s SCRT emission control system.
Encouragingly, Dickinson states that in prototype installations there have been no packaging problems in existing engine bays. The Cobra electric supercharger simply mounts upstream of the turbocharger, using the existing water cooling supply and delivering extra air very fast as required. Furthermore, the conversion doesn’t involve major ECU re-programming. Cobra reads engine speed, etc, from the vehicle Canbus, and calculates when to supply supplementary boost, he says.
“Cobra reduces the [engine] pumping work by reducing the pressure difference between inlet and exhaust manifold. At certain conditions the BSFC can be improved significantly.”
For even greater efficiency gains, Dickinson concedes more integration would be required, along with changes to engine fuelling. However, for the moment CPT’s focus for its electric supercharger conversion is all about the low rev (700—1,000rpm) boost enhancement on large displacement engines.
By teaming up with Eminox, CPT gains a partner already well versed in reducing older engine emissions. Eminox’s service network can also undertake conversions, as could dealers and operator workshops. As for timescales, Pascoe says: “In retrofit terms it could come next year. We also see this as an opportunity for the OEMs over the next three years and beyond.”
There’s certainly plenty to play for. The current consultation from London mayor Sadiq Kahn on bringing forward the proposed Euro 6-based ULEZ to 2019 and extending its scope in 2020 will surely focus the minds of operators, especially bus companies, running non-Euro 6 vehicles. And there are plenty of those: according to a recent study, while some 3,500 Euro 6 buses are now operating in the UK, more than 17,000 are still in service with Euro 5 or below engines.
What about the pay-back? While there’s still some months to go before the CPT/Eminox conversion is available, Dickinson suggests that potential buyers should expect a two-year ROI (return on investment).