Quad 4, and other quandries

Dear Car Talk

Dear Car Talk | Mar 01, 1991

Dear Tom and Ray:

What does the term "Quad 4" mean when speaking of automobile engines?

RAY: Quad 4 is a registered trade mark of the General Motors Corporation. It's GM's name for a four cylinder engine with four valves per cylinder, which is now a pretty common design.

TOM: Traditionally, each cylinder in the engine had two valves--one to let the fuel/air mixture into the cylinder, and one to let the exhaust out after the explosion takes place.

RAY: But engineers figured out that if you used two intake valves and two exhaust valves per cylinder, everything goes in and out faster, and the engine produces more power. And in the last few years, this technology has become cheap enough to use on normal, everyday cars.

TOM: And although General Motors was far from the first company to offer a four valve per cylinder engine, they've demonstrated that they're still among the leaders in marketing jargon. They picked the name "Quad 4" because it harkens back to GM's glory days. It conjures up images of four barrel carburetors, four hundred cubic inch engines, four on the floor transmissions, and forty four percent market shares--all things GM had in the good old days.

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