Golf Course Management

FEB 2017

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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Page 35 of 127

Scott R. Nesbitt Timing troubles Easily overlooked, the timing chain system can be the most important factor in the poor performance of many four-cycle gasoline and diesel engines found in turf equipment and on- road vehicles. Old-timey mechanics used the term "tuneup" to refer to the installation of new parts and adjustments to the fuel-delivery and igni - tion systems of engines. Like a guitar or violin, an engine sounds in good tune when all the op - erating pieces are synchronized and balanced. Modern engines use a computer to achieve proper tuning (top photo). The computer pro - gram makes modifications in response to input data from sensors that report on the movement of the crankshaft and/or the camshaft, the den - sity and temperature of incoming air, the posi- tion of the throttle plate, and the cooling sys- tem's temperature. Output commands adjust the amount of fuel sent to the cylinders and the time at which spark plugs fire in a gasoline engine. "Knock" sensors and oxygen sensors report whether things are out of sync because the plugs are fir - ing too soon, or because the air-fuel mixture is too lean or too rich. The computer is pro - grammed to maximize power and efficiency. All of this electronic wizardry assumes there is proper coordination among the mechanical parts — the crankshaft-piston system and the camshaft-intake-exhaust-valves system. The camshaft must rotate at half the crank - shaft speed, and be synchronized so the valves open and close at exactly the right time as the pistons move up and down. If the cam and crank are close together, a set of gears keeps them connected and coordinated. Most engines use a set of sprockets con - nected by a chain or belt. Chains are mounted inside the engine, sealed in with the lubricat - ing oil. Belts are mounted outside, given that oil destroys them. Belts are made of materials Depending on its program, the computer may refuse to let the engine start, or may switch into low-power "limp" mode while triggering a "check engine" warning light. Replacing the timing chain and sprock - ets can be easy or painful, depending on the engine installation. At the worst, you'll have to pull the engine out to replace the tim - ing chain set. Always follow the factory ser- vice manual to make sure everything is right and tight. Never pound on the sprockets or chain — you can soak the chain in hot oil to make it grow a bit, easing installation. For more on engine management and the role of timing chains, search online for "loose timing chain." Good coverage of engine con - trol can be found at learn-engine-management . Scott R. Nesbitt is a freelance writer and former GCSAA staff member. He lives in Cleveland, Ga. (shop) 32 GOLF COURSE MANAGEMENT 02.17 that don't stretch, so timing remains accurate, but belts must be changed periodically or you risk engine destruction. Engine-makers are increasingly going back to chains, which can last for many decades and thousands of hours. Chains, however, can stretch, and sprockets can wear down, especially if the engine oil gets too thin or contains grit. Stretching increases if the chain's workload rises, because weak oil increases friction as the camshaft lobes slide against the valve train components to open the valves. You see this same effect when you have to frequently tighten a chain saw's chain that has to slide along the bar rails. An engine control computer that uses only one sensor to monitor either the crank or cam cannot know that things are not in sync. A computer that uses both crank and cam sensors will get con - flicting input data. Some engines monitor the camshaft by putting the sensor in the igni - tion distributor, which is rotated by the cam- shaft. This adds more moving parts, increas- ing the chances of an out-of-sync situation. Engine control computer programs may reduce engine power and efficiency when a loose timing chain causes inaccurate data to come from input sensors. Photos by Scott R. Nesbitt Replacing the timing chain set requires disassembling the front of the engine, and that may involve removing lots of chassis components. A chain-and-sprocket system coordinates crankshaft and camshaft positions to set the foundation for fuel, air and ignition control and adjustment.

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