Q. I really like the look of the prominent chrome dual exhausts seen on so many cars and trucks these days. To me, they give a look of masculinity to the vehicle. For years, it seemed that manufacturers installed only single exhausts, except on the most powerful or sporty cars. And in many cases, the exhausts were hidden from view. Are “duals” now being installed more for looks, or do they really enhance performance, fuel mileage, etc.? Thanks.

TOM: Good question. Real dual exhausts will increase performance.

RAY: Here’s the basic tutorial: Fresh gasoline and air go into the cylinders. It gets detonated by the spark plug, it combusts and then it turns into what? Exhaust.

TOM: And before you can send more fresh gasoline in there, you have to get that exhaust out. The faster you can get the old stuff out and the new stuff in, the better your engine “breathes,” and the more power it can produce.

RAY: A lot of manufacturers have made their engines breathe better by adding more valves per cylinder — valves are the holes through which stuff enters and exits the cylinders.

TOM: But another way to improve breathing is to add an additional exhaust pipe. For instance, if you have a V-6 or V-8 engine, you can use one exhaust pipe to take the exhaust from just one bank of cylinders all the way to the back of the car. And you could have a second exhaust pipe for the other bank of cylinders. That gives you twice as much capacity to remove exhaust.

RAY: So it does work. But very few cars actually do it. More often, what you see are fake dual exhausts. There’s actually a single exhaust pipe running from the engine to the muffler, and then the pipe is split, sending one tailpipe to each side of the car. That’s just for looks.

TOM: Then there’s the really cheap version, where the single exhaust pipe goes within inches of the rear bumper, then splits into two exhaust tips at the very end. Neither of those systems will affect performance. But I agree with you — they do enhance the look of a car and make it look more expensive.

RAY: Of course, the problem with a real dual exhaust system is that it is expensive — not only to manufacture, but to maintain. Think about it. When it rusts out, you’ll need to buy TWO new exhaust systems. You’ll be a hero at your local Midas Muffler. The guys’ll have pinup posters of you in every bay.

Q. My son has a 2006 Jeep that he uses to carry around tennis equipment and his dogs. His youngest dog, a 10-month-old, 60-pound male golden retriever, likes to sit in the front passenger seat. He is heavy enough to cause the seat-belt alarm to sound while the car is riding. Of course, this has become very annoying, to say the least! My son tries to get the dog to sit in the back, but he likes looking out the front window. Is there any way to disconnect the alarm so that the bell stops dinging constantly? Any help would be greatly appreciated! Thanks.

TOM: Well, first, we’d like to congratulate the dog on having done such an excellent job of training your son. Most people would start by modifying the dog’s behavior rather than modifying the electronics of their car. But clearly, this dog is very persuasive.

RAY: Your son should move the dog to the back seat. Not only because that will turn off the seat-belt warning, but because it’s safer — for the dog AND for your son.

TOM: Right. Your son carries tennis equipment. What if a tennis ball rolls out from under the driver’s seat, and the dog jumps down into the foot well to get it? He could interfere with your son’s use of the pedals, causing an accident. Or he could shift the car from drive to reverse along the way. Or he could block your son’s view of the road by standing on his lap (a favorite dog trick).

RAY: Or, if there is an accident, the 60-pound dog could get thrown into your son, and depending on where he makes contact, the results could be very ugly.

TOM: Were you thinking of the neck?

RAY: I was thinking of the groin, actually, but having 60-pound dog go flying into your neck would be bad, too.

TOM: A number of companies make car restraints for dogs. They hook onto your existing seat belts. If your son is unable or unwilling to train the dog, the dog should be in the back seat, secured with one of those restraints. Or in a crate in the cargo area. He may not be able to stick his head out the front window from there, but he won’t hit it on any “Yield” signs either.

Got a question about cars? Write to Click and Clack in care of this newspaper, or email them by visiting the Car Talk website at www.cartalk.com.