Low temperature cranking

A new proposed SAE Viscosity Classification not only reflects lower than 0°F temperature cranking characteristics of an oil, but also covers low temperature pumpability characteristics (j), 10). Low temperature cranking success without oil pump-ability could result in oil starvation and subsequent engine damage. This new proposed classification attempts to establish a maximum cranking viscosity and then classifies oils according to what temperature they match this viscosity. It also includes a low shear test (mini-rotor viscometer) to duplicate pumpability of the oil at various low temperatures. Needless to say, minimum... 

Caracciola, F. and McMillan, M. L. SAE Paper 790728, June 1979, "Effect of Engine Oil Viscosity on Low-Temperature Cranking, Starting, and Fuel Economy. ... 

Low temperature performance. The cold crank simulation test is of vital interest to any car owner living in a cold climate. The advantage of a PAO-based formulation in the crankcase is immediate and obvious on a cold winter morning ... 

SAE viscosity grade Low temperature (°C) cranking viscosity (cP, max)b Low temperature (°C) pumping viscosity (cP max, with no yield stress) Kinematic viscosity (cSt) at 100°C mind Kinematic viscosity (cSt) at 100°C mind High shear viscosity (cP), at 150°C and 10 V, mine... 

Diester synthetic base stock lubricants formulated with 2-ethylhexanol (e.g., di-2-ethylhexyl adipate) provide excellent low temperature starting properties in automotive crank case applications and are also employed as lubricants for industrial machinery such as compressors and turbines. 

It should also be mentioned that low oil viscosity at low temperatures is desirable in the new small 4 cylinder and V-6 cylinder fuel economy automobiles ( 5, 6). This is to permit sufficient speed of engine cranking for cold weather starting at winter temperatures. Low oil volatility must be maintained to prevent oil misting and blowby from poisoning the catalyst system and oxygen sensors in the anti-pollution devices (7). 

The cold crank simulator test, ASTM D2602/IP 383, measures the apparent viscosity of an oil sample at low temperatures and high shear rates, related to the cold starting characteristics of engine oils, which should be as low as possible. The oil sample fills the space between the rotor and the stator of an electric motor, and when the equipment has been cooled to the test temperature, the motor is started. The increased viscosity of the oil will reduce the speed of rotation of the motor and indicates the apparent viscosity of the oil. The test is comparative for different oil samples rather than an accurate prediction of the absolute performance of an oil in a specific engine. 

SAE viscosity grade Low-temperature,°C, cranking viscosity, mPa-s, maximum Low-temperature,°C, pumping viscosity, mPa-s, maximum, with no yield stress Low-shear rate kinematic viscosity mm /s at 100°C maximum/minimum High-shear rate viscosity, mPa-s at 150°C, minimum... 

Insufficient crank power at low temperature Engine will not start 8 Cell incorrect design for cold temperatures 2 Validation plan 2 32... 

A similar policy applies for motorcycles and for trucks, with smaller and higher battery capacity, respectively. Specific cold-cranking capability is less an issue for both these types of vehicle. Motorcycles are seldom used under conditions of extreme cold, and truck batteries are, in many cases, so high in capacity that even the low-temperature performance is sufficient for engine cranking. 

Cold cranking simulator The apparent low temperature viscosity of engine oils (ASTM D5293) correlates with the ease of low temperature engine cranking, measured in centipoise rather than centistokes, and the temperature is always given (e.g., CCS at -25°C = 1405 cP). 

Mekonnen and Crank also found the same reaction dichotomy in Friedel-Crafts reactions of 622 (X = O) with acid chlorides or acid anhydrides. In general, acylation of 622 (X = O, R = CH3) with acetic anhydride or benzoyl chloride/ pyridine afforded the corresponding 2-(acylamino)-4-methyloxazole 630a and 630b (Scheme 1.174). However, low-temperature acetylation or aroylation of 622 (X = O, R = CH3) in the presence of two equivalents of AICI3 produced a 5-acyl-2-amino-4-methyloxazole 631 in low to modest yield. The authors reported that AICI3 was the most effective Lewis acid (SnCLj and TiCL) and that the reaction required two equivalents of Lewis acid. Selected examples are shown in Table 1.48. 

Viscosity is a key lube oil property and is a measure of the fluidity of the oil. There are two measures of viscosity commonly used kinematic and dynamic. The kinematic viscosity is flow due to gravity and ranges from approximately 3 to 20 cSt (centistokes) for solvent neutrals and about 30-34 cSt at 100°C for Bright stock. The dynamic viscosity is flow due to applied mechanical stress and is used to measure low temperature fluidity. Brookfield viscosity for automobile transmission fluids (ATF s) at -40°C and cold cranking simulator (CCS) viscosity for engine oils at -25°C are examples of dynamic viscosity measurements. 

The eombined effeets of 4, 5 and 6 means that a properly matehed starter motor ean crank the engine faster at low temperatures while in most cases drawing a smaller eurrent from the battery. This is a very important feature, which enables a further stage of system optimization to take place. 

Lithium-ion batteries are used in Nissan s Tino, a hybrid electric vehicle. The Tino seats five and achieves twice the fuel economy of the corresponding non-HEV car. Only a hundred Tinos will be built and they use Shin-Kobe LiMn204 packs. Saft [11] has recently reported good low temperature performance for cold cranking and projects that a 15-year life should be achievable with LiNiCoOj-based cells. Cost and safety appear to be the only issues now limiting use of lithium-ion batteries in hybrid electric vehicles. 

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