Can "start-stop" technology be added to an older car?

Dear Car Talk

Dear Car Talk | Apr 01, 2011

Dear Tom and Ray:

I wonder if it is possible to take one feature from a hybrid car and use it on a regular car to save gas. When stopped at a red light or stop sign, or dead cold in a traffic jam, why can't a regular car have the feature that simply shuts off the engine and then turns it on again when you hit the gas pedal? Come to think of it, golf carts do this, too. Is it some Foreign Oil or Big Three conspiracy that keeps us from benefiting from this ingenious fuel-saving feature? Or am I missing something very obvious as to why this could not be installed in my trusty 2006 Saturn Ion? -- Luther


RAY: You already have that feature, Luther. It's called the key.

TOM: Actually, you're looking for an automatic system. The good news is that it's on its way. A number of manufacturers are planning to add "stop-start" technology to their non-hybrid new cars in coming years.

RAY: Engineers say that gas mileage can be increased by as much as 5 percent to 10 percent with stop-start, depending on how much you what? Stop and start!

TOM: But you can't easily retrofit it to your 2006 Saturn Ion. The problem is that your car's starting system, which consists of a 12-volt battery and a 12-volt starter motor, is designed to start the car only a few times a day. It's not built to start the engine hundreds of times a day. And it won't hold up over time.

RAY: Even if it did hold up, starting it so many more times would eventually damage the gear on the flywheel. And replacing the flywheel on most cars requires removing the engine and transmission, which runs into big money.

TOM: What you'd need is a more robust starting system, and that's really something you have to design into the car from the beginning.

RAY: A popular system in use by cars that have start-stop systems is a belt-driven alternator that doubles as a starter motor. So when the engine is running, the engine turns a belt, which spins the alternator, which charges the battery. And when the engine's not running, the alternator becomes a starter motor, and it turns the belt, which starts the engine. That avoids the flywheel altogether.

TOM: But while you can't install a system like this on your old Ion, Luther, we're guessing your next new car will have something like this. In fact, we think all cars will have start-stop at some point. Sooner rather than later.

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