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The selection of the correct belt in an automotive power train transmission is not a random decision effected by engineering, but prepared and accurate and affects the timing, accessory drive efficiency and maintenance schedule. A mis-matched belt will result in belt slippage, belt squeal or even valve to piston interference that can result in the total destruction of an engine. It is a critical issue for the fleet buyer, workshop owners and after market distributor. With more than 26 years of professional experience in the manufacturing of automotive V-belts, timing belts and PK-type multi-ribbed belts, Xingtai Guanpin Rubber Products Co., Ltd (Guanpin) has put together this handy guide to help you find belt models in a systematic manner, according to vehicle classification, engine configuration and load.
Decoding the Vehicle Classification – Passenger Cars vs. Commercial Vehicles
In the first step of vehicle matching, the weight of the vehicle and the type of its engine come into play. Multi-ribbed PK belts and toothed timing belts are primarily used in overhead-cam (OHC) engines, mainly for accessory drives (like the water pump, a/c compressor, alternator) and for passenger cars such as sedan, SUVs and crossovers. The length of these belts is usually much shorter (PK4 or PK5) and the lengths which they can be reliably inserted into the hose, measure between 950mm – 1,500mm. Commercial vehicles, such as light trucks, heavy-duty trucks and buses, however, use wider V-belts (AVX or AV series) with deeper cross-sections for transmitting greater torque from their diesel engines. Between these two families are divided the production lines, with different structures of rubber compounding (higher heat resistance for turbo-diesel uses) and tensile cords constructions. Now it is important to know if it is a petrol or diesel engine, and if petrol whether it is a naturally aspirated or turbocharged engine, to identify the lowest and highest possible temperatures for the engine to operate in and the maximum belt tensions.
Engine Type Specifics – OHC, OHV, and Pushrod Architectures
The valvetrain design is the most important factor when selecting a timing belt. The timing belts used on the overhead-cam engines (single or dual cam) must be highly dimensionally stable in order to ensure the synchronization of the crankshaft and camshafts. In these applications, Guanpin belts have very little elongation of the tensile cord during their service life of 60,000 - 100,000 km, and the tensile cord made from high-modulus glass-fiber, aramid are used. The tooth profile to be used should be the same as that of the sprocket. Asian and most European OHC engines have a trapezoidal or curvilinear (HTD) tooth form. A few of the American OHV V8 engines still employ more industrial-style timing belts of a wider pitch. Do not normally use timing belts on pushrod or flathead type engines; make note of timing belt for accessories (serpentine). Guanpin tech team will be able to cross-reference more than 500 engine families on request with an engine code (stamped on the cylinder block).
Interpreting Belt Specifications – Length, Ribs, and Angle
In model matching, the length (Effective length (mm), for model V-belts the number of ribs or top width, for V-belts the included angle) are the key factors for measurement. A typical example of designation is 6PK1250 which indicates 6 ribs and profile thickness (rib pitch = 3.56mm) & 1250mm effective length (for PK belts) for Pk type serpentine belts. Measuring the belt outside circumference or using a laser pulley gauge to measure center distances are the requirements for belt matching. V belts are available in widths AV10 through AV25 and have the typical angle of 40° (for auto use) or 30° (for some Japanese kei cars). Guanpin always guarantees that its belts can be interchanged with OEM belts and complies to ISO 9981 (for PK belts) and DIN 7753 (for V-belts). Note: If your belt is 10mm longer than it should be, it will slip and overload the belt and same goes for a faulty 10mm short belt that will overload bearings. Please always provide the Vehicle's VIN/Engine serial number with bulk orders and Guanpin will compare your target engine with its application database and determine the exact Guanpin model number for you.
Environmental and Load-Based Adjustments – Air Conditioning and Power Steering
Belt loads are another important factor determining belt selection and service life, aside from type of engine. Variable tension requirements on the same belt can be as high amperage alternators (start-stop systems), dual A/C compressors (minibuses), or hydraulic power steering pumps. If this is the case, Guanpin suggests making a change from standard eprd compound to a nitrile compound in a state of highly saturated nitrile or a hydrogenated nitrile (HNBR) compound which can keep flexible running performance under cyclic thermal shock condition and the range is from -30℃ to +150℃. For Tropical climates (high humidity and dust) think of anti-static belts as well as covers that resist the ozone. Remember the accessory pulley number: If accessory pulley uses too many or too few ribs, the belt will wear out or slip off the pulley. Guanpin's Sales Engineers frequently help customers choose the right belt width and compound according to the local operating condition. Enter the regular duty cycle and ambient temperature range of your fleet and get suggestions that fit the situation.
Finally, belt matching is a methodical procedure based on a vehicle class, the design of the engine valvetrain, dimensions, and the type of accessories for load-profile integration. Xingtai Guanpin Rubber Products Co., Ltd. is a more than rubber v-belt, timing belt and PK belt supplier who can also provide application consulting for bulk buyers free of charge! It is Guanpin's 26 years experience which covers from the compact, light load truck of Japan, to the luxury sedan of Europe and the heavy duty pickup of the USA, with belts that fit, perform and last. Please call Guanpin's export department with your engine codes and we will be able to match your needs with 100% accuracy for a model verification or if you request sample kits for testing and verification for fit.