In addition to a heavy-duty starter, start-stop systems require such components as enhanced engine control, battery management, DC/DC converters, and more robust crankshaft sensors.
(Source: Robert Bosch LLC)
I have always believed that the hybrid was the most innovative and effective improvement on the ICE-based motor vehicle, and past short personal experiences with the Prius (as a rental) were nothing but positive; actually spectacular, iin my view.
The outcome of a recent negative vehicular experience, has me now driving a Ford Escape Hybrid. Just the evolution from 15-16 mpg to 29-31 mpg has been a god-send, and the performance experience has been very admirable. Clearly, there is a start-stop component to the vehicle propulsion system, and I must say it is quite seamless. Watching the tach go from 1000 rpm to zero, either on coast, or stop is quite gratifying. Quite frankly, there is nothing negative I have yet encountered about the vehicle itself or the technology. Clealry , Ford has gotten it right.
I don't understand the discussion about the need to synchronize the starter to restart when a car is at substantial speed. A starter motor is not needed when the momentum of the car can be used (as almost anyone who has driven a standard shift car before steering wheel locks knows). Restaring an engine at speed effiicently is only a matter of reconnecting the engine to the wheels and then knowing the right time to put in fuel and spark. With electronically actually valves it is even easier because rengaging the engine is even more seamless if the valves are held open. Engine managment computers make all of this relatively easy.
For start-stop driving, it would be very easy to have a small hydraulic accumulator to apply full oil pressure before cranking begins. It would take less than a second to bring up the oil presure and about another second to flood all of th bearings. So there would not need to be a lack of oil pressure concern.
One other thing is that with manual control it is easy to get much better than the ten percent reduction in fuel consumption while driving in rush-hour type traffic. Adding the coasting to the stopping does a great job of reducing fuel consumption. At least, that was my experience.
I also agree that improvements to regular gas-powered car engines are not hybrids.
My 2012 Honda Civic turns off the engine when coasting (standard 1.8 litre gasoline). The tires spinning on the road surface, going through the drive-train, keeps the engine spinning. The automatic transmission downshifts when decelerating to keep the engine speed above about 1,200 RPM. The engine automatically turns back on when the gas pedal is used, at speeds below about 10 miles per hour, and when stopped. When coasting, the instantaneous fuel economy gage is pegged at 70 miles per gallon. For best fuel economy, I try to coast as much as possible, especially during city driving.
Of course when stopped, the engine is running and using gas...and that's zero miles per gallon. That's the main advantage of "start-stop", not using gas when stopped. For best fuel economy, I avoid driving around looking for a better parking spot, fast food drive-thru's, and even red lights (when possible).
I will never buy a car with an electric starter - the convenience does not outweigh the cost and the inconvenience of having to repair it when it breaks. And, one crank handle can be used to start many different cars - no need for awkward jumper cables.
This is fascinating but I certainly can see engineering hardware and software challenges with this technology. I am definitely going to follow up with GOOGLE searches to learn more about those automotive companies with systems already in place and being testing. Charles, do you feel this technique would be adaptable to 400 Hp diesel engines--in other words, 18 wheelers? Great post and very informative.
"A study was done years ago that said about 80% of engine wear happens in the first few seconds after starting because of lack of oil pressure."
It is my understanding that the 80% wear referred more to cylinder wall wear as opposed to engine bearing wear. Most wear occurs before cylinders come up to normal operating temperatures and properly mate with pistons and piston rings. It was quite common to see air cooled Volkswagen cylinders with over 100,000 miles that have no wear ridge at the top because they warmed up so fast.
With start-stop technology, certainly oil would not drain off bearings completely. As mentioned, pre-oil systems are already available to combat cold start bearing wear should that prove to be a problem. Study the maintenance history of the U.S. Postal System vehicles if you desire more data, as they are mandated to shut down between stops. Starters and associated systems will definitely be a problem, but one that can be mitigated with a more robust design.
Since this was first posted, I have learned that at least one Canadian city is making it illegal to idle for more than 60 seconds! Stated concern: polution at stop lights during the winter months (inversion layer during winter?)
If this comes even close to being enforced (70%+), a lot of older cars are going to see a lot of their local mechanics! Older cars are simply not designed for this level of abuse.
time and tide wait for no one......
I was kinda hoping to keep my older sports car for alot longer.. .(sigh)
George Leopold's talk at last week's Design & Manufacturing Minneapolis helped restore astronaut and engineer Gus Grissom's role in the beginnings of NASA, and outlined how Grissom played a pivotal role in winning the Space Race.
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