Sustainable America Blog

Engine Start-Stop Systems

As we continue our initiative to end unnecessary idling, we wanted to take a closer look at an existing technology that could go a long way to reduce the needless burning of gas at stoplights and drive thrus: engine stop-start systems. Although this technology has been around since the 1980s in Europe, American automobile manufacturers have only recently started to utilize it. Increasingly strict fuel economy standards in the United States, Asia, and Europe and sustained high gas prices are driving demand for this fuel-saving feature.

So what is an engine stop-start system? This anti-idling technology automatically turns the engine off when the vehicle is stopped and immediately restarts when the driver presses the accelerator or lifts off the brake/clutch. This feature is available in nearly all hybrid vehicles but has only recently been introduced into conventional cars. Interestingly enough, the cost is more reasonable than consumers may think — between $300 and $400, according to some industry analysts. Aside from the environmental benefits, with gasoline prices close to $4 a gallon, a $300 stop-start system could pay for itself in three years or less.

The adoption of this technology in the United States has been slow going. Luxury brands like Audi, BMW, Mercedes-Benz and Porsche have been among the first to introduce it in some 2012 models. Jaguar added stop-start to its 2013 XF and XJ sedans, and Kia plans to debut stop-start systems in upcoming 2013 Soul and Rio models. Ford’s 2013 Fusion will be the first domestic car with a stand-alone stop-start system, with others, like Chrysler Group, expected to follow.

With the praise for these new systems also comes some criticism. “Heating and cooling is one of the big challenges in stop-start development,” says Stephen Poulos, GM’s chief engineer for eAssist and battery-electric propulsion systems. (GM models with the eAssist mild hybrid system include a stop-start system.) “If you stop the engine, how do you keep the temperature in the cabin comfortable?”

This could obviously become an issue at extended stops, like railroad crossings or long red lights. Full hybrid systems, such as Toyota’s Prius, use an electric air-conditioning and heating system that isn’t dependent on the car’s internal combustion engine. Additionally, GM developed control logic for it’s eAssist system that maintains cabin temperatures for up to two minutes when the engine is stopped.

Another downside of stop-start systems is the extra strain they put on the car’s battery, which must kick in to keep things like the lights, radio and air conditioning humming when the engine shuts off. However, Milwaukee-based Johnson Controls, a leading global manufacturer and supplier of advanced batteries used in stop-start systems, says it has not experienced any increase in warranty claims due to premature battery failures in the batteries they sell for use in European cars with start-stop systems.

A few recent technological advances have the potential to help solve the the battery issue. Australia’s CAP-XX Ltd is developing “supercapacitors,” which can provide high-power support to automotive stop-start systems, protecting and extending the operating life of the car’s battery in the process. Lighter than a battery, they can operate at low temperatures and be charged/discharged almost infinitely. Panasonic has developed a battery system that harnesses and stores energy when the brakes are applied, which in turn runs the car’s electronics. And Texas-based Molecular Rebar Design has found a way to use carbon nanotubes to improve battery life by 50% to 70%.

Performance can also be an issue, with some drivers reporting unexpected jolts when the engine restarts. Consumer Reports found variances in performance with the start-stop systems by make and model. For example, testers driving the BMW 328i Porsche Cayenne last year complained that the engine was rough when restarting. On the flip side, testers said driving the Chevrolet Malibu Eco delivered “silky-smooth restarts every time.”

Potential downsides aside, Johnson Controls predicts that up to 40 percent of all new cars and light trucks sold in the U.S. in 2015 could be equipped with engine stop-start systems and expects global production of the systems to rise from 3 million a year today to 35 million a year in 2025. And a new report by advanced technologies specialist Pike Research. forecasts that the number of vehicles in the U.S. market with engine stop-start systems could more than triple from 3 million in 2015 to 10 million by 2020.

Until the day that stop-start technology is as common as cruise control and cup holders, we can all do our part the old-fashioned way: by turning off our vehicles when we’ll be idling for more than 10 seconds. Learn more about idling and support us in our quest to end unnecessary idling by pledging to quit at iturnitoff.com.

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By the Numbers

Currently 50 million households suffer from food insecurity, meaning that family members cannot always meet their basic food needs.

10 million people a year could be fed through the recovery of just one-fifth of food waste.

Only 2% of food waste is composted or otherwise recycled—62% of paper is recycled.

Consumers throw out about 40% of the fresh and frozen fish they buy.

The U.S. produced 208 pounds of meat per person in 2009—60% more than Europe.

Low income commuters spend a much higher proportion of their wages on gas—8.6% versus 2.1% at $4 per gallon.

Food prices rose 35-40 percentage points between 2002–2008.

Americans consume 25% of the world’s produced oil, but our nation holds less than 3% of the world’s proven oil reserves.

The International Energy Agency says greenhouse gas emissions rose 3.2% last year, with a 9.3% increase in China offsetting declines in the US and EU.


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