A great question, RFB, and a wonderful opportunity to talk about some basics in the way the internal (eco-freaks say "infernal") combustion engine works. My shiny new Webster's Unabridged (Christmas present from my Editor...is this a comment on my grammar?) defines combustion as "2. rapid oxidation accompanied by heat and usually, light." Can you say explosion? The internal combustion engine is an explosion machine. It takes air and gasoline in one end, lights a fire, causes an explosion and shoves the residue out the other end. Over and over and over. Of course, it's moving the pistons up and down and turning the crankshaft as a by product at the same time. It has also been called an air pump. Sucking air in, adding fuel, squeezing the mixture, lighting it off, burning it and exhausting the leftovers. What lets the air in and out? Valves, of course. One for intake, one for exhaust. And that's the way it mostly was until about 15 years ago when Detroit was made to get serious about energy conservation, fuel economy and emissions control. The race for smaller, lighter, more fuel efficient and cleaner burning engines began in the early '80s with the imposition of emission control regulations and CAFE (corporate average fuel economy) requirements.

MIGHTY MITES

So here's what 4-valve engines have that 2-valve engines don't. Greater throughput of air. Smaller valves mean less weight. Less weight means less energy needed to open and close them. It also means lighter valve springs to hold them closed. All of which means that the engine can safely spin at a higher RPM which again, increases the power output for a given engine displacement.

By the way, it's not true that all current engines are 4-valve. Many are still 2-valve for cost reasons. At the same time, so-called multi-valve engines are spreading. There are now many V-6 engines with 24 valves and V-8s with 32 valves. Ferrari builds a gorgeous 48-valve, 12-cylinder engine. And now we are seeing some 5-valve production engines. By the way, this 4-valve technology is not new. They were building racing engines in the '30s with 4 valves and turbochargers.

HOT TIPS-SURE THINGS AND LUCKY GUESSES

GET A CHARGE OUT OF THIS Check the purchase date on your battery. If you are nearing the end of the warranty period, start looking for sale prices now. Don't wait until you have no choice.

David Thompson is President of Auto Testers, Inc., publishers of The New Driver Car Control Clinic, a program to help parents make their new drivers safer drivers.
Questions should be addressed to info@carcontrol.com or:

The Auto Advisor
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