Thoughts on the supercharged engine...

Dear Car Talk

Dear Car Talk | Jan 01, 1990

Dear Tom and Ray:

I read your comments on the decreased longevity of turbo-charged engines. You said that these particular engines don't last as long as their non-turbo counterparts. What are your general feelings about the supercharged V-6 engine that is now being sold in the Ford Thunderbird SC and the Mercury Cougar XR-7. Do you think the supercharged engine will last longer than a turbo-charged engine?

RAY: We drove a Thunderbird with the supercharged V-6 and liked it very much--particularly with the automatic transmission. But with any type of "charging," you do pay a price for all that power.

TOM: Like turbo-charging, supercharging increases engine power by forcing extra air into the combustion chamber. But the two systems work in different ways.

RAY: A turbo-charger is a turbine that spins at a very high speed. The turbine is powered by the pressure of the engine exhaust. When it spins, it forces fresh air into the combustion chamber; that's what provides the turbo-boost. The amount of turbo "lag" is determined by how long it takes the exhaust pressure to get the turbine spinning. Most turbos take a few seconds to kick in--providing boost when the engine reaches about 2500 rpm.

TOM: A supercharger does not rely on engine exhaust for power. It's a separate blower driven by a notched belt off that runs off the crankshaft. That means it's running all the time--so there's less "lag" with a supercharger.

RAY: Turbo-charging is harder on the engine because every time the turbo kicks in, it really jolts the engine components with that surge of power. Since superchargers provide more gradual boost, they are somewhat better.

RAY: Both systems would be fine if their purpose was to give a fuel efficient but somewhat wimpy engine a little bit of extra power once in a while--like while passing on a hill or entering an expressway. But everybody knows that the people who buy turbos and superchargers buy them for performance, and not to save gas--you wouldn't be interested in a supercharged Subaru Justy, would you?

TOM: The harder you drive these cars--the more "boost" you use--the faster you wear out the engine's moving parts. So our advice depends on the reason you're buying the car. If you feel you can get by with a smaller, fuel efficient engine 99 percent of the time, but would like a little reserve power for those times you need it, a turbo-charged or supercharged car is fine.

RAY: If, on the other hand, you are buying a car with the intention of driving the lugnuts off of it, why not just start off with a bigger engine. A bigger engine will give you the power you're looking for, and is better equipped to handle the abuse we know you're going to give it. Whichever way you decide to go, Darryl, don't ever expect to take MY teen-age daughter out on a date!

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