TROY, MI – If cars of the next decade turn out as global auto supplier Delphi wagers, drivers will be the big winners with thrifty fuel economy and performance punch.

Delphi, a U.K.-based electronics specialist and onetime captive parts maker to General Motors, is placing a big, but well-reasoned, bet on 48V technology in the coming years. The supplier thinks penetration of the advanced stop/start system will reach 12.5 million installations globally by 2025, according to third-party estimates, as automakers strive to meet tightening carbon-dioxide and fuel-economy regulations without sacrificing drivability or deploying fleets of expensive hybrids and plug-ins.

A seat-of-the-pants evaluation by WardsAuto editors here of a Delphi prototype suggests the supplier’s bet is a sure thing.

In most applications, 48V technology replaces a vehicle’s traditional alternator with a motor-generator backed by a small, lithium-ion battery. The system does not replace the vehicle’s conventional lead-acid battery; instead, it provides extra power when the vehicle shuts down at a stop and helps restart quickly and smoothly. Regenerative braking replenishes the li-ion battery.

But it also can efficiently run other vehicle systems and components, such as the adjustable suspension on the new Bentley Bentayga midsize CUV or the electric supercharger of the upcoming Audi SQ7 large CUV. Fuel savings can be upwards of 15%, or a 10% slash in carbon-dioxide emissions, according to estimates.

The Honda Civic-based prototype Delphi provided to WardsAuto editors for a few loops around its campus north of Detroit uses 48V technology to run an electric turbocharger, or e-charger, to boost performance of the car’s 1.6L diesel engine. Delphi says the car delivers a 10% reduction in CO2 emissions compared with a standard Civic Earth Dreams turbodiesel.

The prototype, which Delphi had borrowed from its European operations where principle development is taking place to showcase 48V technology to investors and local journalists, includes two driving modes for experimentation: one with the system engaged and a second with it disengaged.

In the traditional driving mode, where 48V technology is turned off, the manual-transmission Civic performs like a standard turbodiesel. There’s a good bit of grunt, but it works best at mid-range and higher engine speeds. At lower rpms, which drivers could encounter during stop-and-go traffic, there’s excessive turbo lag and drivability is subpar.

Switch on the 48V power, and the turbo lights up immediately. Even if you’re nearing a stall, the technology delivers quick pick-up. Turbodiesel owners know to keep their engine speeds up for optimal performance, but in traffic congestion you can sometimes get caught in the wrong gear and stomping the throttle returns nothing. It can be irritating, but also dangerous in heavy traffic. Delphi’s 48V technology eliminates that quirk by providing a 25% increase in torque below 1,000 rpm.

The supplier’s 48V system solves another emerging quirk on the road to improved efficiency: sluggish stop/start performance. Vehicles with stop-start, a big fuel-saving play becoming commonplace technology around the world, oftentimes take an extra split-second at the stoplight because of the restart. Like turbo lag, it can be a turnoff for drivers new to the technology. Stop/start is particularly difficult to match with diesels because of their high compression ratios, a whopping 16:1 on the Civic.

However, Delphi’s 48V unit provides a lightning-quick restart, as well as a little dose of electric power to get the car moving more quickly off the line. There is very little engine shudder as the car shuts down and restarts, compared with many cars that rely solely on 12V power and come on and off like a farming implement.

As is the case with many new technologies, 48V is not entirely perfect. There’s an added cost to the consumer of between $1,000 and $2,000, although that is one-third the investment of strong-hybrid technology. The li-ion battery adds weight, too, which in some applications could negate the fuel-economy gain. In the Delphi prototype, however, there is no spare tire so it is an even tradeoff.

Delphi sees itself as an integrator on 48V technology, tying together hardware from strategic partners with its software and electronics expertise to create tailored packages for OEMs.

For example, the prototype uses a li-ion battery and starter-generator from Magneti Marelli. The e-charger comes from Honeywell. Delphi provides the remainder, such as the power-distribution unit, controllers and engine management and mild-hybrid software, a DC/DC convertor to marry 12V with 48V and sealed connectors for the unit’s wiring.

Delphi has begun work on a second-generation 48V system, which will add Dynamic Skip Fire cylinder deactivation technology. Currently under testing in a GMC Yukon Denali large SUV, DSF and 48V promise a 25% fuel-economy gain in cars such as the Delphi prototype.

Delphi says its 48V technology will launch in products from two unidentified OEMs by the end of the year.