Offering everything from silent starts to high-torque speed boosts with ultra-low emissions, the powerful integrated starter-generator’s capabilities appear to be a technician’s dream.

But it also might be a supplier’s nightmare. Engines could shed a host of time-tested components, from the gear-toothed flywheel and starter motor to alternators and other belt-driven accessories.

Adoption of any integrated starter-generator system also will mean large cost increases for both power generation and battery storage over today’s conventional systems, says Gary Cameron, chief engineer of Delphi Automotive Systems Corp.’s Energenix working group.

“If you just look at integrated starter-generator systems as producing electricity, it’s probably a multiple of three to five times more expensive than what you have on the electrical system today, roughly. The key to making the value work on these things is what you enable with this system,” Cameron says.

That same factor of three to five times current costs applies to the battery systems needed to manage the power generated and used by integrated starter-generator systems, compared with today’s relatively modest 12-volt battery costs, he says.

ELECTRIFIED GOLF

Siemens Automotive Corp. engineer Jorg Lehmann has placed an integrated starter-generator in the 1.6-liter engine of a Volkswagen Golf, a relatively heavy car by European standards. His team also installed a technically advanced automatic-manual transmission in the package.

Siemens chose the Golf because it already provided the engine control unit for the car. But the prototype is meant as a technology demonstrator only. There are no plans at VW to build a Golf equipped with the system.

Even in the demonstrator, though, Lehmann says the ability of the system to stop an engine and restart it, rather than having it run at idle speed, already is good and continues to be refined.

“There is a problem for the driver to get his foot off the brake and to the accelerator pedal as fast as this engine starts,” he says, citing times of 0.3 seconds to spin an engine past 500 rpm. Conventional starter motors typically take about 1.2 seconds to crank an engine to life.

But fast – and silent – starts aren’t the only key to the system’s impending arrival in production cars.

It’s the ability to turn an internal combustion vehicle into what the industry has termed a mild hybrid, driving a 42-volt electrical system that excites automakers.

COLD-START CURE

The systems have many different names, including start/stop generator; integrated starter alternator; and Integrated Starter Alternator Damper, which was trade named by ContiTech and shown in a prototype in 1998.

The device will allow automakers to use smaller, less gas-hungry engines because its electric torque helps speed off from a stop and uses an electric motor turbo boost when speed increases are needed on the road.

That lets a light-displacement gasoline engine work efficiently, maintaining speeds and charging batteries for the next boost.

Integrated starter-generator systems also are expected to reduce emissions during cold start and initial low-speed driving, the time when the heaviest tailpipe emissions occur.

While moving the car with its internal electric motor, the internal combustion engine’s output is used to heat the catalytic converter. When emissions system conditions are ideal, the engine begins to share more of the driving load. This feature requires some advanced battery technology.

Finally, the integrated starter generator may turn the harshest engine into a purring kitten. The device can pulse to cancel torque peaks in the driveshaft, smoothing the output of otherwise unacceptable powerplants. That capability could speed the introduction of new, clean-burning small diesel engines in cars.

“You have hit upon a key interest,” says Franz Wressnigg, president of Siemens Automotive Systems Group.

Wressnigg and Siemens engineers say that using a starter-generator makes it possible to reduce the compression ratio in light diesels while creating the kind of steady-state operating environment that is the engine’s strength.

Other companies also have tied the devices to diesel.

DaimlerChrysler’s Dodge ESX3 concept, the result of the company’s Partnership for a New Generation of Vehicles work, uses a three-cylinder 1.5-liter diesel equipped with permanent-magnet integrated starter alternator supplied by Delphi.

Wressnigg says Siemens already has worked with one small-car manufacturer that believes a starter-generator type system makes it possible to offer a low-cost car by equipping the vehicles with a smaller, cheaper gasoline engine. He would not identify the vehicle or its maker but indicated it was not a North American manufacturer.

“You should not only take into consideration the electrical architecture but that you can reduce the engine size,” Wressnigg said.

KEY TO REDUCED EMISSIONS

Francois Castaing, former Chrysler executive vice president in charge of vehicle engineering, says the starter devices are crucial for getting improvements in fuel economy without a tailpipe emissions tradeoff.

“The cornerstone is a starter alternator integrated with the flywheel, something like that, and a new battery system. Maybe the first step will be a beltless engine with electronically controlled water pump, and electric steering and air conditioning,” Castaing said during a panel discussion at the Convergence 2000 meeting in October in Detroit.

Norio Omori, Denso Corp. senior managing director of engineering r&d, says that to reach fuel economy and carbon dioxide emissions targets already set to be introduced in Europe, small to medium-sized cars will need a motor-generator system driven by 42-volt power.

“A hybrid vehicle including the 42-volt stop and start, minor or major (electrical) regeneration and electric vehicle driving at low speed will be necessary to meet that requirement,” Omori says.

COST MAJOR FACTOR

Harry Husted, senior systems engineer for Delphi Automotive Systems, warned that cost is a major factor in discussions of mild hybrids and starter systems. Delphi has named its system Energen 10 and believes it offers promise in fuel economy gains over its investment price.

“The value of a hybrid powertrain has to be greater than its cost. That’s very simple but also very profound,” Husted said.

That means that the move to starter-generator systems may begin with an interim solution – essentially a heftier belt-driven alternator that can act as a starter motor.

The system abandons some of the benefits of a true starter generator, particularly torque pulse damping, but does not require the total engineering change of a starter generator.

“Most of our competitors are offering induction machines on the crankcase housing; we’re offering it here and implementing many of the same functions,” said Daryl Wilson, Visteon Corp.’s technical representative for Energy Transformation Systems.

Visteon showed a water-cooled start/stop alternator designed in partnership with Gates Rubber, which supplies a toughened serpentine belt as part of the system, during Convergence 2000.

Wilson says that such systems offer an affordable, evolutionary way to move to a start/stop engine system.

“Delphi also has developed a start/stop belt-driven alternator, the Energen 5, and recently demonstrated an air-cooled version during the Paris auto show.

“We think it could be well suited for applications in small cars in Europe.

“There’s not that much lateral space in the engine compartment for the system, where this belt drive off to one side can fit,” Cameron says.

He believes a mix of technologies – air-cooled start/stop alternators, liquid cooled alternators and starter-generators – will come to automobiles in the era of 42-volt systems. But Cameron also believes voltages in cars will inevitably increase, demanding further refinements to meet fuel and environmental challenges.

Other engineers view the alternator as a low-cost but potentially time-consuming diversion on the path to true integrated starter systems.

But with 42-volt systems virtually assured for power-hungry cars of the next decade, all agree some form of integrated start/stop system is coming. Today ’s rasping, squealing starter motors will go to join the hand crank in the halls of automotive nostalgia.