Cold time of year always brings problems to motorists. Looking for other tires, oil, fuel, liquid for washing windows - and all you name it.
Many of the cars is becoming difficult to run - frost requires a good state of power systems, ignition. starter battery. And we have to change the spark, high voltage wires, adjust the engine ...
But everything seems normal. The engine can now be easily run in any frost. However, one question still remains - whether it is necessary to warm up the engine or mowho immediately after the launch of touch As a way? The question is not so simple as it seems, even among specialists there is no consensus.
To answer it, you need to track which processes occur in the engine is cold, and that changes upon heating.
At that affects temperature?
To get started please refer to the structure. It is known that engine parts are often made of different materials: for example, one of the mating parts - aluminum, while the other - steel or cast iron.
And if the thumb in the piston, camshaft in the cylinder head or the body at low temperatures will have small gaps, then as the warm-up due to difference in the coefficients of thermal expansion of aluminum and steel (iron), the gaps become larger.
On the contrary, in a pair of piston - cast iron cylinder block or liner, at low temperatures, the gap would be great. Further, when the engine warms it drops to desktop, and in case of engine overheating - and completely to zero.
Obviously, the particular change in performance gaps have a major impact on the character of lubrication, friction and wear. Consider these questions in more detail.
Piston usually has a nominal gap in the cylinder of about 0,04 - 0,06 mm at 20 ° C. When the air temperature when the engine is smaller gap increases in proportion to the temperature difference. If the frost reaches 30 ° C, the gap in the cylinder will increase by half - to 0.08 - 0.1 mm.
With this gap, the piston can knock Changing roll, ie, passage of the upper and lower dead point. A engine with worn piston group with higher clearances of pistons in cylinders, will start work after noisy. And only after warming up the noise will be less.
Designers typically try to reduce "cold" sound of the pistons, pushing a finger on the 0.5 - 1.5 mm from the axis of the piston. Then the pressure of gases during combustion creates a force on the piston, preventing blow the skirt of the cylinder wall during roll direction at top dead center. However, this method does not operate in all modes of operation of the engine and remove the tap completely impossible.
Since the sound of the piston appears in the event of an impact piston skirt on the surface of the cylinder. it causes accelerated wear. Therefore, the work of the engine on these conditions - the right tool significantly reduce its longevity.
But the cold piston knock - not all problems. As we know, the colder the street, the more enriched fuel mixture should flow into the cylinders to ensure reliable starting, and engine performance. In this case, the excess fuel entering the cylinder in the form of drops, washes oil from its walls.
This is further exacerbated by the conditions of the piston in the cold engine - in some cases may cause scuffing at the piston skirt, piston rings and cylinder, leading to an increase in oil consumption, decrease compression. True, in modern engines to solve this problem by choosing materials for the parts, as well as the application of special coatings on them.
Experience has shown that if the engine is idling, hard punches roll direction when the piston does not arise. Another thing, when the cold engine running under load, for example, during acceleration and driving. It is on these conditions and there are usually defects on the working surfaces of parts.
A somewhat different picture emerges in the other pairing, for example, where aluminum parts comprises a steel or cast iron.
For example, piston pin installed in the holes of the piston bosses with a gap of about 0.01 mm at a normal temperature of 20 ° C). If cold start is carried out at -30 ° C, the joint gap is close to zero. Enough when you start the engine to give greater momentum or start a movement, and may happen next.
Rapid rotation of the finger in the hole without a gap and also when there is insufficient lubrication (thickened oil is not immediately begins to flow to the rubbing pairs) leads to a marked increase in friction. This causes rapid heating of the contact surfaces, as well as the piston can not warm up soon, the diameter of the holes for the first time is not increased, but decreased as a result of the finger may jam into him deny the piston.
At least dangerous situation is possible and camshaft bearing. He is most remote from the oil pump, and after starting the oil to him go on last. At low temperatures and too viscous oil camshaft bearings may have "oil starvation" within a few tens of seconds after launch.
The result will depend on the mode of operation of the engine: at low speeds possible jamming of the shaft in the bearings, and high - their fusion with the severe damage the shaft and cylinder heads. Lack of lubrication - one of the main causes of failure at cold start and warming up the engine.
So in the cold season should be attentive to motor oil - primarily to use oil with proper viscosity. We should not forget about the quality of the oil determined by its specification. Oil of poor quality are sometimes prone to the formation of low-temperature deposits nA internal parts and surfaces of the engine, particularly in circumstances where warm-up time to operating temperature increases significantly.
By the way, because of this winter of frequent travel on short distances without the engine warms up unsafe - bad oil is quite capable of turning into some mysterious substance that covers the walls with a thick layer of ointment and oil clogging the channels and holes.
In modern engines, with very compact design, the channels of lubrication system, tend to have small cross sections. Because of this engine is very sensitive to the viscosity of the oil - if at cold start it is too large, no oil will flow to the bearings for a long time with all the ensuing consequences. Obviously, there is a risk of defects is possible, using synthetic oil with a stable temperature viscosity.
So warming or not warming?
Without a doubt, our brief analysis of the processes in the engine shows that from a technical point of view, it should warm up. And you can even specify under what conditions - no load at idle, with a somewhat increased frequency of rotation. And until then. until the coolant temperature does not rise to at least 40 - 50 ° C (the temperature gauge "stragivaetsya with zero-stop, which takes an average of two to five minutes depending on temperature).
