Torque converter9/19/2023 ![]() ![]() Adhere to the manufacturer's recommended specifications for testing. Whatever the malfunction, mpg will be decreased.ĪCTIVITY: Complete the torque converter activity sheet. Internally, the lockup device itself could fail or wear out. Sensors - temperature, speed, selector position, engine vacuum - may fail wiring and connectors could fail or become disconnected. Lockup torque converters may exhibit additional fuel-eating malfunctions. The transmission may shift normally even when the one-way torque converter clutch slips or fails to release properly! Top cruising speeds are lowered to 40 or 50 mph. The failure results in a 30 to 50% reduction in mpg. Vehicles with a non releasing one way clutch will accelerate normally but at a decreased top speed. A vehicle with a slipping one-way torque converter clutch will experience a 20 to 30% decreased fuel economy.Ī one-way torque converter clutch that does not release is a second type of torque converter failure. Mpg will be significantly reduced since engine torque is not being multiplied during acceleration. If the one-way torque converter clutch slips, then the vehicle will characteristically have very poor acceleration. Internal failure will reduce mpg and affect vehicle performance. If any one sensor fails to complete the string, the converter will not lockup. Some manufacturers add additional parameters to converter lockup. Transmission must have shifted into the top gear. Vehicle must be in a cruise or near cruise condition. Vehicle must be at or above minimum lockup speed. Transmission selector must be in drive if a non-overdrive vehicle or in "O" or "OD" overdrive if an overdrive vehicle. Coolant must be at or above minimum temperature. Therefore, for most converters to lockup, the following must be present:Ī. That is, if one sensor gives a "no" signal then the converter will not lockup. Typical lockup converters connect these sensors in a series creating a "string" arrangement. To prevent engine lugging, which could result in serious engine damage, a sensor determines if low manifold vacuum exists. Under low engine vacuum, heavy part-throttle acceleration is an additional power demand which could result in the engine lugging. Overdrive lockout would normally only be used when pulling heavy loads, thus the converter is logically "locked out."ģ. Overdrive unit locked out - when an automatic overdrive is "locked-out" the torque converter lockup feature will also be locked out. Engine temperature too cold - most converters will not lockup until the coolant reaches about 120☏.Ģ. Besides the speed sensing indicator, a converter may not lockup for any of the following reasons:ġ. Other factors may also prevent this type converter from locking up. This lockup feature will not engage until the vehicle reaches approximately 40 mph. Recently developed torque converters have had a "lockup" feature added to reduce this energy loss and improve mpg. This energy loss is transmitted to the vehicle's radiator and shed as heat. This accounts for most of the mpg difference between a standard and automatic transmission vehicle. At this point, the converter is said to be "coupled hydraulically." Under these conditions, up to 10% of the engine's output power could be lost to the torque converter's internal slippage. Once turbine speed is approximately 90% of impeller speed, the one-way clutch race spins on its own axis. This action aids an automatic transmission vehicle's acceleration capacity. (See Figure 1 for the torque converter part relationship.) Internally, torque converters use a one-way clutch device to multiply engine torque at low engine RPMs. Some energy is lost between the input (the impeller) and the output (the turbine) sections. Torque converters are not 100% efficient. All automatic transmissions use a torque converter to couple the engine and transmission. OBJECTIVES: The student will identify common, standard non-lockup torque converter and common lockup torque converter malfunctions that can result in reduced mpg. GOALS: To understand the relationship between a malfunctioning lockup torque converter and reduced fuel economy. Torque Converters and Fuel Economy TORQUE CONVERTERS AND FUEL ECONOMY ![]()
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