It's the little things that count. Start-stop technology, in which your car's engine shuts down when you're stopped at a red light or sitting in gridlock but automatically restarts when you lift your foot from the brake pedal, will likely be standard equipment in 20% of all cars by 2015. It has proven to be reliable, cheap to manufacture, and it could save millions of barrels of oil a year and hundreds of tons of greenhouse emissions.
Now transmission maker ZF Friedrichshafen AG has introduced a technology that improves on the efficiency of start-stop. It's called hydraulic impulse oil storage, and it makes for faster starts while also saving fuel. The system supplies the hydraulic oil the eight-speed tranny needs for starting within 350 milliseconds. Fuel consumption on starts is reduced by 5%.
The technology uses a spring piston accumulator which fills with oil and "tensions" as the car engine runs. When the engine starts up, this "reserve" of around 100 centiliters is flushed to the hydraulics, supplying oil to the shift elements. The results are faster starts using less gas.
