Optimum turns of the petrol engine 1.6. Is it worth turning the engine? What is harmful high crankshaft speed

26.09.2019

Salon

A LOT of letters, but everything is on point!
WITH “WEDGE”
Instructors who teach to drive “pull-in”, at minimum speed, have not been translated into driving schools - they say, this way the engine will wear out less. Some of them even bend the pedal or put a wooden stop under it - then, with all your desire, you will not fully open the gas. So then another driver drives - with a “wedge”, frightened, as soon as the tachometer needle crosses the 2000 mark. This style is justified by fuel economy, caring for the engine.
As for fuel economy, this is only partly true. At low revs, the engine does not pull, so when overtaking or on a more or less noticeable rise, an adherent of this driving style is forced to “tread” the gas pedal, further enriching the mixture and burning the saved fuel.
So, maybe we win in the resource? At first glance, the answer is obvious: less engine speed means lower relative speeds of movement of parts, and wear decreases accordingly. But not everything is so simple. The most critical plain bearings (camshaft, main and connecting rod journals of the crankshaft) are designed to operate in hydrodynamic lubrication mode. Pressurized oil is fed into the gap between the shaft and the bushing and perceives the resulting loads, preventing direct contact of the parts - they simply “float” on the so-called oil wedge. The friction coefficient for hydrodynamic lubrication is extremely small - only 0.002-0.01 (for lubricated surfaces with boundary friction it is ten times higher), therefore, in this mode, the liners withstand hundreds of thousands of kilometers. But the oil pressure depends on the engine speed: the oil pump is driven by the crankshaft. If the load on the engine is high and the speed is low, the oil wedge can be pressed through to the metal, and the liner will begin to break, and wear progresses rapidly as the gaps grow: it is more and more difficult to create a “wedge”, there is not enough oil supply.
In addition, when driving at low speeds, there are shock loads in the engine and transmission. The inertia of the rotating parts is no longer sufficient to smooth out the resulting vibrations. The same thing happens when touching. Recall a driving school: as soon as you release the clutch sharply at low gas, the car starts to jump. Sometimes this ends with a breakdown of the clutch: the elastic plates of the driven disk fastening to the casing do not withstand, burst, springs pop out of the windows. It is better to lose a little on wear and tear, but to avoid premature failure.
So, the more we demand from the motor (sharp acceleration, rise, loaded car), the higher the speed should be. And vice versa, with a quiet ride, when the engine is lightly loaded, it makes no sense to drive the tachometer needle to the end of the scale.
GOLDEN MEAN
Accelerated wear of the liners is not the only evil from the passion for low speeds. During short trips in such modes, low-temperature deposits accumulate in the engine, primarily in the lubrication system. It’s worth “grabbing” along the highway - and hot oil under pressure will thoroughly flush the system, at the same time, excess carbon deposits in the combustion chambers and piston grooves will burn out. Sometimes it is possible to restore the compression in the cylinders that has decreased due to the occurrence of rings.
When disassembling the “Zhiguli” motor, many paid attention to the worn recesses on the end of the valves - traces of levers. These marks mean that the valves did not rotate, but worked all the time in one position. Meanwhile, the rotation of the valve prolongs its service life, only this is possible at speeds above 4000-4500 rpm. Few bring the motor to these modes, so a notch appears on the valves. And then she herself will prevent their rotation.
But long work near the red zone is also not good for the engine. Cooling and lubrication systems are working to the limit, without a margin. The slightest defect of the first - a radiator clogged with fluff in front or sealant from the inside, a faulty thermostat - and the arrow of the temperature gauge will be in the red zone. Bad oil or clogged lubrication channels can cause scuffing on parts or even “sticking” of liners or pistons, breaking the camshaft. Therefore, “racers” should not lose sight of the pressure gauge and temperature gauge. A serviceable engine, filled with good oil, tolerates maximum speed without problems. Of course, in this mode, its resource is reduced, but by no means catastrophically - if only the spare parts were not “left”!
Between these two extremes lies the golden mean. Depending on the specific conditions, the optimal mode is 1/3-3/4 revolutions of maximum power. In the break-in mode, too low revolutions are also unacceptable, and the upper limit should be lowered to 2/3 of the “maximum speed”. But the main principle remains unshakable - the higher the load, the higher the speed should be.
COLD START
Starting in the cold is not good for the engine. Gasoline condensed on the cold walls of the cylinder does not burn out, but dilutes and washes away the oil film from them. Therefore, high speeds are harmful to an unheated engine, and old carburetor engines do not pull at low speeds. Injection engines allow you to drive right away, but it’s better to wait a minute until the oil scatters a little through the system and goes to all nodes.
Oil starvation can occur immediately after start-up if the oil does not have time to return to the sump and air cooler pump. Therefore, if the low oil pressure light comes on, immediately turn off the engine for 30-40 seconds - let it drain. The reason can be either too thick oil, or its insufficient level or a clogged oil receiver (ZR, 2002, No. 4, p. 188).
HEATSTROKE
This danger lies in wait for the driver, who is always in a hurry: having won some seconds in a crazy race, he flies up to the sidewalk, turns off the ignition and ... at the same moment, the engine temperature begins to rise. A second ago, the thermal balance of the engine running at high speeds was maintained due to the intensive circulation of the coolant and the cooling of the radiator. But the pump pumping it over stopped, and the pistons, valves, cylinder head are still very hot. Sometimes the liquid even has time to boil, and the steam removes heat hundreds of times worse. After several such overheating, the cylinder head may be deformed, its gasket may burn out - the repair is not cheap.
There is only one way out - after an active drive, let the engine cool down at idle for at least 15-20 seconds. This is especially important on turbocharged engines. Replacing a failed turbine will cost much more than the time saved.
THE MORE WE NEED FROM THE MOTOR (SHARP ACCELERATION, LIFT, LOADED VEHICLE), THE HIGHER RPM SHOULD BE
OPTIMAL MODE - 1/3 - 3/4 TURNS OF MAXIMUM POWER
HIGH RPM FOR A WARM ENGINE IS HARMFUL
AFTER AN ACTIVE RIDE, ALLOW THE ENGINE TO COOL AT IDLING

September 13, 2017

The mode of operation of the engine is one of the main factors affecting the wear rate of its parts. It is good when the car is equipped with an automatic transmission or a variator that independently chooses the moment of switching to a higher or lower gear. On machines with “mechanics”, the driver is engaged in switching, who “spins” the motor according to his own understanding and not always correctly. Therefore, motorists without experience should study at what speed it is better to drive in order to maximize the life of the power unit.

Low speed driving with early shifting

Often, driving school instructors and old drivers recommend that beginners drive “in tension” - switch to a higher gear when the crankshaft reaches 1500–2000 rpm. The first give advice for safety reasons, the second - out of habit, because before the cars had low-speed engines. Now this mode is only suitable for a diesel engine, whose maximum torque is in a wider rev range than a gasoline engine.

Not all cars are equipped with tachometers, so inexperienced drivers with this style of driving should be guided by speed. The early shift mode looks like this: 1st gear - moving from a standstill, shifting to II - 10 km / h, to III - 30 km / h, IV - 40 km / h, V - 50 km / h.

Such a shifting algorithm is a sign of a very relaxed driving style, which gives an undoubted advantage in safety. The downside is an increase in the wear rate of parts of the power unit, and here's why:

The oil pump reaches its nominal capacity from 2500 rpm. The load at 1500–1800 rpm causes oil starvation, especially connecting rod plain bearings (liners) and compression piston rings.
Conditions for combustion of the air-fuel mixture are far from favorable. In the chambers, on the valve plates and piston bottoms, carbon deposits are heavily deposited. During operation, this soot is heated and ignites the fuel without a spark at the spark plug (detonation effect).
If you need to rev the engine sharply when driving downhill, you press the accelerator, but acceleration remains sluggish until the engine reaches its torque. But as soon as this happens, you shift into a higher gear and the crankshaft speed drops again. The load is large, there is not enough lubrication, the pump poorly pumps antifreeze, hence overheating occurs.
Contrary to popular belief, there is no fuel economy in this mode. When you press the gas pedal, the fuel mixture is enriched, but does not burn completely, which means it is wasted.

It is easy for owners of cars equipped with an on-board computer to be convinced of the uneconomical movement "in tightness". It is enough to turn on the display of the instantaneous fuel consumption.

Such a driving style wears out the power unit intensively when the car is operated in difficult conditions - on dirt and country roads, with a full load or trailer. Owners of cars with powerful engines of 3 liters or more, capable of accelerating sharply from the bottom, should not relax either. After all, for intensive lubrication of rubbing engine parts, you need to keep at least 2000 rpm of the crankshaft.

Why is high crankshaft speed harmful?

The driving style “sneaker on the floor” implies constant crankshaft spinning up to 5–8 thousand revolutions per minute and late gear shifting, when engine noise literally rings in the ears. What is fraught with this driving style, in addition to creating emergency situations on the road:

all components and assemblies of the car, and not just the engine, experience maximum loads during the service life, which reduces the overall resource by 15-20%;
due to the intense heating of the engine, the slightest failure of the cooling system leads to a major overhaul due to overheating;
exhaust pipes burn out much faster, and with them an expensive catalyst;
transmission elements wear out rapidly;
since the crankshaft speed exceeds the normal speed by almost twice, the fuel consumption also increases by 2 times.

The operation of the car "at break" has an additional negative effect associated with the quality of the road surface. Driving at high speed on rough roads literally kills the suspension elements, and in the shortest possible time. It is enough to fly the wheel into a deep pothole - and the front strut will bend or crack.

How to ride?

If you are not a race car driver and not an adherent of tight driving, who finds it difficult to retrain and change driving style, then to save the power unit and the car as a whole, try to keep the engine operating speed in the range of 2000-4500 rpm. What bonuses will you receive:

The mileage before the engine overhaul will increase (the full resource depends on the brand of car and engine power).
Thanks to the combustion of the air-fuel mixture in the optimal mode, you can save fuel.
Fast acceleration is available at any time, you just need to press the accelerator pedal. If there is not enough speed, immediately switch to a lower gear. Repeat the same steps when moving uphill.
The cooling system will function in operating mode and protect the power unit from overheating.
Accordingly, suspension and transmission elements will last longer.

Recommendation. On most modern cars equipped with high-speed gasoline engines, it is better to change gears when the threshold of 3000 ± 200 rpm is reached. This also applies to the transition from higher to lower speed.

As mentioned above, car dashboards do not always have tachometers. For drivers with little driving experience, this is a problem, since the crankshaft speed is unknown, and the beginner does not know how to navigate by sound. There are 2 options for resolving the issue: buy and install an electronic tachometer on the dashboard or use a table that shows the optimal engine speed in relation to the speed in different gears.

Position of the 5-speed gearbox	1	2	3	4	5
Optimum crankshaft speed, rpm	3200–4000	3500–4000	at least 3000	> 2700	> 2500
Approximate vehicle speed, km/h	0–20	20–40	40–70	70–90	over 90

Note. Considering that different brands and modifications of machines have different correspondences between the speed and the number of revolutions, the table shows average indicators.

A few words about coasting from a mountain or after acceleration. In any fuel supply system, a forced idle mode is provided, which is activated under certain conditions: the car is coasting, one of the gears is engaged, and the crankshaft speed does not fall below 1700 rpm. When the mode is activated, the supply of gasoline to the cylinders is blocked. So you can safely brake the engine at top speed without fear of wasting fuel.

Almost every driver is well aware that the resource of the engine and other components of the car directly depends on the individual driving style. For this reason, many car owners, especially beginners, often think about what speed is best to drive. Next, we will consider what engine speeds you need to keep, taking into account different road conditions during the operation of the vehicle.

Read in this article

Engine life and revs while driving

Let's start with the fact that competent operation and constant maintenance of optimal engine speeds can increase engine life. In other words, there are operating modes when the motor wears out the least. As already mentioned, the service life depends on the driving style, that is, the driver himself can conditionally “adjust” this parameter. Note that this topic is the subject of discussions and disputes. More specifically, drivers are divided into three main groups:

the former include those who operate the engine at low speeds, constantly moving "pulled".
the second should include such drivers who only periodically spin up their motor to above-average speeds;
the third group is considered to be car owners who constantly maintain the power unit in a mode above medium and high engine speeds, often driving the tachometer needle into the red zone.

Let's understand in more detail. Let's start with driving on the "bottom". This mode means that the driver does not raise the speed above 2.5 thousand rpm. on gasoline engines and holds about 1100-1200 rpm. on diesel. This style of driving has been imposed on many since the days of driving school. Instructors authoritatively state that it is necessary to drive at the lowest speeds, since in this mode the greatest fuel economy is achieved, the engine is loaded the least, etc.

Note that in driving courses it is advised not to turn the unit, since one of the main tasks is maximum safety. It is quite logical that low speed in this case is inextricably linked with driving at low speeds. There is logic in this, since slow and measured movement allows you to quickly learn how to drive without jerks when shifting gears on cars with manual transmission, teaches a novice driver to move in a calm and smooth mode, provides more confident control over the car, etc.

Obviously, after obtaining a driver's license, this driving style is further actively practiced on your own car, developing into a habit. Drivers of this type begin to get nervous when the sound of an untwisted motor begins to be heard in the cabin. It seems to them that the increase in noise means a significant increase in the load on the internal combustion engine.

As for the engine itself and its resource, too “sparing” operation does not add to its service life. Moreover, everything happens exactly the opposite. Imagine a situation when a car is moving at a speed of 60 km / h in 4th gear on smooth asphalt, the speed is, say, about 2 thousand. In this mode, the engine is almost inaudible even on budget cars, fuel is consumed minimally. At the same time, there are two main disadvantages in such a ride:

there is almost no possibility of accelerating sharply without downshifting, especially to "".
after changes in the road surface, for example, on slopes, the driver does not downshift. Instead of shifting, he simply presses harder on the gas pedal.

In the first case, the motor is often outside the “shelf”, which does not allow you to quickly disperse the car if necessary. As a result, this driving style affects the overall driving safety. The second point directly affects the engine. First of all, driving at low revs under load with a strongly depressed gas pedal leads to detonation of the motor. The specified detonation literally breaks the power unit from the inside.

In terms of fuel consumption, the economy is almost non-existent, as more pressing on the gas pedal in high gear under load causes a richer air-fuel mixture. As a result, fuel consumption increases.

Also, “pull-in” driving increases engine wear even in the absence of detonation. The fact is that at low speeds, the loaded rubbing parts of the motor are not sufficiently lubricated. The reason is the dependence of the performance of the oil pump and the engine oil pressure it creates on all the same engine speeds. In other words, plain bearings are designed to operate under hydrodynamic lubrication conditions. This mode involves the supply of oil under pressure into the gaps between the liners and the shaft. This creates the desired oil film, which prevents wear of the mating elements. The effectiveness of hydrodynamic lubrication is directly related to engine speed, that is, the higher the speed, the higher the oil pressure. It turns out that with a heavy load on the engine, taking into account the low speed, there is a high risk of severe wear and breakage of the liners.

Another argument against driving at low speeds is a reinforced engine. In simple words, with a set of revolutions, the load on the internal combustion engine increases and the temperature in the cylinders rises significantly. As a result, part of the soot simply burns out, which does not happen during constant operation on the "bottom".

High engine speed

Well, you say, the answer is obvious. The engine needs to be revved more strongly, as the car will respond confidently to the gas pedal, it will be easy to overtake, the engine will be cleaned, fuel consumption will not increase so much, etc. This is true, but only in part. The fact is that constant driving at high speeds also has its drawbacks.

High speeds can be considered those that exceed the approximate figure of about 70% of the total number available for a gasoline engine. With the situation is slightly different, since units of this type are initially less revving, but have a higher torque. It turns out that high revolutions for engines of this type can be considered those that are behind the “shelf” of diesel torque.

Now about the engine resource with this driving style. Strong spinning of the engine means that the load on all its parts and the lubrication system increases significantly. The temperature indicator also increases, additionally loading. As a result, engine wear increases and the risk of engine overheating increases.

It should also be borne in mind that at high speed modes, the requirements for the quality of engine oil increase. The lubricant must provide reliable protection, that is, meet the declared characteristics for viscosity, oil film stability, etc.

Ignoring this statement leads to the fact that the channels of the lubrication system may become clogged during constant driving at high speeds. This happens especially often when using cheap semi-synthetics or mineral oil. The fact is that many drivers change the oil not earlier, but strictly according to the regulations or even later than this period. As a result, the liners are destroyed, disrupting the operation of the crankshaft and other loaded elements.

What speed is considered optimal for the motor

To save engine life, it is best to drive at such speeds, which can conditionally be considered average and slightly above average. For example, if the “green” zone on the tachometer suggests 6 thousand rpm, then it is most rational to keep from 2.5 to 4.5 thousand rpm.

In the case of atmospheric internal combustion engines, designers try to fit the torque shelf in this range. Modern turbocharged units provide confident traction at lower engine speeds (the torque shelf is wider), but it is still better to spin the engine a little.

Experts say that the optimal operating modes for most motors are from 30 to 70% of the maximum speed when driving. Under such conditions, minimal damage is caused to the power unit.

Finally, we add that it is periodically desirable to spin up a well-warmed and serviceable engine with high-quality oil by 80-90% when driving on a flat road. In this mode, it will be enough to drive 10-15 km. Note that this action does not need to be repeated frequently.

Experienced motorists recommend spinning the engine almost to the maximum once every 4-5 thousand kilometers traveled. This is necessary for various reasons, for example, so that the cylinder walls wear out more evenly, since with constant driving only at medium speeds, a so-called step can form.