4-3-stepen-szhatiya.html

4.3. Compression degree

From the end of a step of compression there is a high pressure of compression which at combustion топливовоздушной mixes sharply continues to increase. For pistons and piston rings, sleeves of cylinders, valves, saddles of valves, linings of cores of valves, and also linings of a head of the block of cylinders it means influence of high thermal and mechanical loading. More often such symptoms as unsatisfactory work at cold start-up or an incorrect course of the engine, the increased expense of oil and fuel, white or dark blue «the exhaust loop of a smoke», the raised water temperature, the worsened parametres of the fulfilled gas or capacity decrease declare itself in due course "creeping" defects of the engine.

If in due course there are suspicions that you Mondeo became less temperamental, than in the first days capacity losses, it is possible to explain the above-stated reasons. Global representation can be received in the event that each 60 000 kilometres to check compression degree. It concerns not only carburettor, but also diesel engines.

Rating values of degree of compression

Values of degree of compression for yours Mondeo differ, depending on compression degree in each cylinder, slightly. Our nominal parametres concern engines at their appropriate mechanical condition. Naturally, at interpretation of degree of compression it less depends on absolute limiting values, than from proportional values in all cylinders. Deviations to a maximum still can be met 2 bar. Besides, it is necessary to consider and errors of the expert. At the first stage it checks your engine by means of the device for check on tightness.

Quite normally – old engines create smaller degree of compression

In old engines compression degree is inevitably lowered. This fact should not become the basis for anxiety as it less «depends on absolute limiting value, than from probably proportional value in all cylinders». As soon as the measured value will reach, it is necessary to be adjusted in the spiritual plan for extensive repair or engine replacement if the difference with the cylinder makes more than 3 bar on the basis of practical experience it can be a consequence of following reasons:

Deterioration of pistons and piston rings, The got stuck, worn out piston rings – it is caused by the rests of combustion of fuel in ring flutes, Oval working surfaces of cylinders – often it is a consequence easy зажатия of the piston or got stuck piston rings, The rests of burning or the dried up oil on cores of valves or surfaces of saddles of valves, Hammered valves, The burnt down valves – it is caused by presence small клапанного a backlash or thermal overloads.

Preset values of degree of compression

Skilled fans-technicians can measure, of course, compression degree independently. For this purpose the assistant who turns the engine by means of a starter, and компрессометр is necessary to them. However, in well equipped workshop of the motorist such компрессометр concerns base equipment. In the beginning unscrew all spark plugs (in the diesel engine of an atomizer) from a head of the block of cylinders and be convinced that valves have "backlash". During check your assistant should press a gas and coupling pedal while you "wring out" the cylinder behind the cylinder. As diesel engines always soak up the same volume of air (internal formation of a mix) in diesel Mondeo the assistant can put "to the left" a gas pedal. It is expedient to begin with the first cylinder and further to go on a number of cylinders. Consider turns of a cranked shaft before achievement of the maximum pressure and take this value as scale of a criterion for other cylinders. The pressure of compression, the "more strong" the cylinder is fast created. According to practice, in the healthy engine the maximum pressure is created for approximately 6–8 turns.

Base for the reliable given measurements – the strong starter, the charged accumulator

It already became almost common truth, however we all the same will stop on this place more particularly: base for reliable results of measurements are a starter with powerful traction force and the charged storage battery. For if the cranked shaft only "wearily" rotates, in the inlet pipeline the gas column is created reluctantly – and measurement in this case is not meaningful. If you have established presence of the big deviations continue carrying out of the test for pressure loss further. The reference with this device, naturally, assumes presence of some practical experience – therefore our council: charge carrying out of the test for losses of pressure to experts.

How to find a trace of errors

At small degree of compression drop by means of a manual butterdish of a few engine oil in apertures of spark plugs (an atomizer aperture in diesel engines) and repeat measurement. It condenses space between the piston and a cylinder wall is better. If value all the same does not change, recognise that pressure goes down in valves, saddles of the valves, directing valves, in a head of the block of cylinders or a lining of the block of cylinders. If more good results of measurement of pressure it means that deterioration in piston rings or a working surface of the cylinder have been received.