How does the gas pedal work?
Q: I get in the car and step on the gas and the car takes off. How does this work? How does the engine respond to my foot on the gas pedal?
— R.H., Hinsdale, Illinois
A: It’s all about air and how much of it enters the engine. From carburetors to computer-controlled fuel injection, the science has remained the same. Press the pedal and the throttle plate opens to allow the air to get sucked in. Most engines rely on a mass airflow sensor located ahead of the throttle plate to measure the airflow and then, based on that data, the injectors squirt the right amount to maintain an air-fuel ratio of exactly 14.7 to 1.
Q: I do not understand the constant call for people to slow down and save gas, a call being re-emphasized as gas prices zoom up. Why is that a proper call? Here’s my thinking. The sticker on any car in any showroom states the mpg for city driving and the one for highway driving; the latter is always higher because one is driving faster and less encumbered. Fuel is being more efficiently used when one is cruising unimpeded down the highway. I get better mileage (by far) in highway driving as against stop-and-start driving. As I see it faster, less-impeded driving is more economical than grandpa’s driving mode. — T.B., Winter Park, Florida
A: As speed increases, drag, caused by pushing air, also increases. There is an optimum speed above which fuel economy suffers. I could quote the formula that the Society of Automotive Engineers (SAE) developed, but only an engineer would probably get it. I certainly don’t. Like Sammy Hagar sang, “I can’t drive 55.” But it might help.
Q: I own a 1965 Chevy Impala, 283 CID, 4-BBL, 2-speed Powerglide, dual exhaust convertible. My very first car back in 1971 was a ’65 Impala but, as most of us did, I trashed it. I bought this one in 2005, and when I go to car shows, there sometimes are discussions as to what car holds the record as the most manufactured automobile in a single year. I have heard that the ’65 and ’66 Impala hold the record consecutively and have, so far, never been surpassed. Can you verify this for me? — B.O., Fishkill, New York
A: I had a 1965 Impala SS, dark green metal flake, 283 CID, 4-barrel Rochester carb, tucked and rolled interior. It was trashed by someone who rear-ended me. I miss that car. Now it’s my turn to do the asking: Dear readers, can you help me answer B.O.’s question?
Q: Should small engines on lawnmowers and snow throwers, etc. be run dry at the end of the season or does that cause damage? — B.K., Riverwoods, Illinois
A: Although doing so is a good idea, many of us are probably too lazy to run the tank dry. It is easier to just add some fuel stabilizer such as Sta-Bil, which helps avoid varnish buildup, especially in the carburetor. You can’t cause damage by running out of gas.
Bob Weber is a writer and mechanic who became an ASE-certified Master Automobile Technician in 1976. He maintains this status by seeking certification every five years. Weber’s work appears in professional trade magazines and other consumer publications.
His writing also appears in automotive trade publications, Consumer Guide and Consumers Digest. Send questions along with name and town to motormouth. tribune@gmail.com.