The Mild Hybrid Approach

It’s the case of on the one hand and on the other: OEMs want to achieve improved fuel efficiency yet they also want to keep costs down.

It’s the case of on the one hand and on the other: OEMs want to achieve improved fuel efficiency yet they also want to keep costs down.

And there is the same this-and-that so far as consumers go: they want to have good fuel economy yet they don’t want to sacrifice performance.

While not exactly a complete solution to meeting these needs on all fronts, Mary Gustanski, vice president of Engineering & Program Management for Delphi, the supplier that has a wide array of capabilities ranging from electrical and electronic products to infotainment systems to safety electronics and sensors, suggests that 48-volt mild hybrid systems can be a viable answer.


Gustanski explains that by replacing the alternator with an electric motor and adding a 48-volt battery and a associated hardware and software, there can be fuel efficiency improvements that are on the order of 50 percent to 70 percent of the fuel-savings provided by a full hybrid system at about 30 percent of the cost.

What’s more, whereas, she says, there is an increasing number of vehicles with start-stop systems, there tends to be underwhelming performance when the accelerator is pressed following a stop (one consequence of which is that while start-stop systems help conserve fuel, some people shut the systems off due to this lag). So, she continues, the mild hybrid approach can supplement the start-stop system, and provide the sort of low-end torque that drivers are looking for.

All of which is to say that there are the benefits of improved fuel efficiency, reduced CO2 emissions, cost effectiveness, and performance through the deployment of 48-volt mild hybrid systems.

Another technology that Gustanski says can have real benefit as regards meeting fuel economy and emissions regulations is “dynamic skip fire.” While there are cylinder deactivation systems in use under the hoods of many engines today, Gustanski explains that they deactivate a fixed number of cylinders.

With dynamic skip fire, the number of cylinders deactivated is continuously variable, depending on load conditions. So rather than, say, deactivating three cylinders of a six-cylinder engine, it might be possible to shut off four, or maybe two.

Gustanski talks about all this and more on this edition of “Autoline After Hours,” where Christie Schweinsberg of and Joe Szczesny of the Oakland Press and The Detroit Bureau join me.


In addition to which, Schweinsberg, Szczesny and I discuss the new 2017 Prius Prime plug-in hybrid (this is a full hybrid, not mild), Volkswagen’s and Mercedes’ electric vehicle strategies announced at the recent Paris Motor Show (I.D. and EQ, respectively), and September auto sales.

And you can see it all right here: