Competent technicians always have been comfortable with basic arithmetic, including the placement and meaning of decimal points.
After all, this is a science-and-numbers business.
Too many tire dealers and service shop operators, however, think that advancements in vehicle technology as well as in diagnostic equipment nearly have eliminated the need for basic math know-how. Baloney! Techs don't need to know integral calculus or differential equations, but they should recognize the importance of the decimal point and how that decimal point got to its assigned location. They also should understand the concepts of positive and negative values.
For one thing, these things are all vital to making accurate measurements-and measurement is the basis of all knowledge. For another, understanding basic math and numbers gives a tech a vital perspective on just how big or small certain measurements really are. This perspective helps reinforce the importance of properly maintained electrical and hydraulic circuits.
Rest assured that competent carpenters know when a fraction of an inch makes or breaks, for example, a door frame installation. Plumbers understand the concept of correct slope (the rise over the run) because slope ensures that pipes drain reliably and efficiently.
In our service bays, though, we encounter measurements that carpenters and plumbers don't. For instance, competent techs are comfortable with common Latin and Greek prefixes. Latin prefixes indicate a value less than one; Greek prefixes indicate values greater than one.
Milli (1,000) is a common, critical prefix techs use. Because it's Latin-derived, it really means one-thousandth (1/1,000) because these prefixes apply to values less than one (1.00). When a spark plug fires, for instance, it typically arcs for about 2 milliseconds. In other words, it sparks for about 2/1,000th (0.002) of a second. A spark plug that arcs for a considerably shorter or longer time indicates a problem.
When an engine is warmed up fully and running at idle speed, the ignition control module usually has to turn on the ignition coil for about 5 milliseconds in order to store enough electrical energy to fire the spark plugs. That means the primary ignition circuit charges the coil with energy for about 5/1,000th or 0.005 second. Sometimes an engine misfires because a failing ignition module cannot keep the ignition coil turned on for the proper period of time. (Old timers knew this ``on'' period as the dwell period.)
An engine control computer may turn on a fuel injector for about 3 milliseconds at idle. That's 3/1,000th or 0.003 second at idle. When you floor the gas pedal to accelerate quickly, that injector ``on'' time typically increases to about 10-11 milliseconds. If it doesn't, the engine runs poorly. The most common cause of this condition is sensor failure under the hood. The appropriate sensors failed to tell the computer that you mashed the gas pedal; consequently the computer didn't respond to the condition correctly (ie., ``garbage in, garbage out'').
When that engine is warmed up and idling, it takes about 10,000 volts to start the arc across the spark plug gap. This is a value greater than 1.00, so we use a Greek prefix kilo (thousand). Therefore, an ignition oscilloscope would show this measurement as 10 kilovolts (10 KV). When a poorly maintained engine misfires during acceleration due to worn spark plugs, the oscilloscope may show an excessive value such as 25,000 volts (25 KV).
Meanwhile, vital values such as fuel trim are displayed in positive or negative numbers. For instance, positive fuel trim readings mean the computer's richening the air/fuel mixture; negative readings mean the computer's leaning out the mixture. Good techs know there's a whale of a difference between making that mixture richer or leaner. Similarly, some pressures we measure are positive ones (fuel, transmission, power steering) but others are negative ones. Vacuum really is a negative pressure.
Simple math skills help consumers spot when the waiter has totaled the tab incorrectly. Out in the bays, it helps good techs recognize when something on an ailing vehicle doesn't ``add up.''