In materials about cars, the expressions "high revs", "high torque" are often used. As it turned out, these expressions (as well as the relationship between these parameters) are not clear to everyone. Therefore, we will tell you more about them.
Let's start with the fact that the engine internal combustion It is a device in which the chemical energy of the fuel combusted in the working area is converted into mechanical work.
Schematically, it looks like this:
Combustion of fuel in the cylinder (6) causes the piston (7) to move, which in turn causes the crankshaft.
That is, the expansion and contraction cycles in the cylinders drive crank mechanism, which, in turn, converts the reciprocating motion of the piston into rotational motion of the crankshaft:
What the engine consists of and how it works, see here:
So, essential characteristics of the engine are its power, torque and revolutions at which this power and torque are achieved.
Engine speed
The commonly used term "engine speed" refers to the number of revolutions of the crankshaft per unit of time (per minute).
Both power and torque are not constant values, they have a complex dependence on engine speed. This relationship for each engine is expressed by graphs similar to the following:
Engine manufacturers strive to ensure that the engine develops maximum torque in the widest possible range of revolutions ("the torque shelf was wider"), and maximum power was achieved at rpm as close as possible to this shelf.
Engine power
The higher the power, the great speed develops auto
Power is the ratio of the work done over a period of time to that period of time. In rotary motion, power is defined as the product of torque and angular velocity rotation.
Engine power has recently been increasingly indicated in kW, and previously traditionally indicated in horse poweroh.
As can be seen in the above graph, maximum power and maximum torque are achieved at different crankshaft speeds. The maximum power for gasoline engines is usually achieved at 5-6 thousand rpm, for diesel engines - at 3-4 thousand rpm.
Power graph for diesel engine:
In practical terms, power affects the speed characteristics of a car: the higher the power, the higher the speed the car can develop.
Torque
Torque characterizes the ability to accelerate and overcome obstacles
Torque (moment of force) is the product of force per lever arm. In the case of a crank mechanism, this force is the force transmitted through the connecting rod, and the lever is the crankshaft crank. The unit of measurement is Newton meter.
In other words, torque characterizes the force with which the crankshaft will rotate, and how well it will overcome the resistance to rotation.
In practice, the high engine torque will be especially noticeable during acceleration and when driving off-road: at speed the car accelerates more easily, and off-road the engine can withstand loads and does not stall.
More examples
For a more practical understanding of the importance of torque, we will give a few examples on a hypothetical engine.
Even without considering the maximum power, some conclusions can be drawn from the graph reflecting the torque. Let's divide the number of revolutions of the crankshaft into three parts - these will be low, medium and high revolutions.
The graph on the left shows a variant of the engine that has high torque at low rpm (which is equivalent to high torque at low speeds) - with such an engine it is good to drive off-road - it will "pull" out of any quagmire. The graph on the right shows an engine that has high torque at medium revs (medium speeds) - this engine is designed for use in the city - it allows you to quickly accelerate from traffic lights to traffic lights.
The following graph characterizes an engine that provides good acceleration even at high speeds - this engine is comfortable on the track. The graphics are closed by a universal engine - with a wide shelf - such an engine will pull out of the swamp, and in the city it allows you to accelerate well, and on the highway.
For example, a 4.7-liter gasoline engine develops a maximum power of 288 hp. at 5400 rpm, and a maximum torque of 445 Nm at 3400 rpm. A 4.5-liter diesel engine installed on the same car develops a maximum power of 286 hp. at 3600 rpm, and the maximum torque is 650 Nm with a "shelf" of 1600-2800 rpm.
The 1.6-liter X engine develops a maximum power of 117 hp. at 6100 rpm, and the maximum torque of 154 Nm is achieved at 4000 rpm.
The 2.0-liter engine delivers a maximum power of 240 hp. at 8300 rpm, and a maximum torque of 208 Nm at 7500 rpm, being an example of "sportiness".
Outcome
So, as we have already seen, the relationship between power, torque and engine rpm is quite complex. In summary, we can say the following:
- torque responsible for the ability to accelerate and overcome obstacles,
- powerresponsible for maximum speed car,
- and engine speed everything is complicated, since each value of revolutions has its own value of power and torque.
In general, everything looks like this:
- high torque at low rpmgives the car traction for off-road driving (such a distribution of forces can boast diesel engines). In this case, the power may become narrower secondary parameter - remember, at least, the T25 tractor with its 25 hp;
- high torque (or better - "torque shelf) at medium and high revsmakes it possible to accelerate sharply in city traffic or on the highway;
- high power engine provides high top speed;
- low torque (even at high power) will not allow the engine to be realized: Being able to accelerate to high speed, the car will reach this speed for an incredibly long time.
The engine operating mode is one of the main factors affecting the rate of wear of its parts. It's good when the car is equipped automatic transmission or a variator that independently chooses the moment of transition to a higher or lower gear. On cars with "mechanics", the driver is engaged in switching, who "spins" the engine according to his own understanding and is not always correct. Therefore, motorists without experience should study at what speed it is better to drive in order to maximize the life of the power unit.
Driving at low speeds with early shifting
Often, driving school instructors and old drivers recommend that beginners drive "tightly" - switch to top gear when reaching 1500-2000 rpm of the crankshaft. The first give advice for safety reasons, the second - out of habit, because earlier the cars had low-speed motors. Now such a mode is suitable only for a diesel engine, whose maximum torque is in a wider rpm range than gasoline engine.
Not all cars are equipped with tachometers, so inexperienced drivers with this driving style should be guided by the speed. The mode with early switching looks like this: 1st gear - moving from a standstill, transition to II - 10 km / h, III - 30 km / h, IV - 40 km / h, V - 50 km / h.
This shift pattern is a sign of a very relaxed driving style, which gives a clear advantage in safety. The downside is in increasing the rate of wear 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 starvationespecially suffer connecting rod bearings sliding (liners) and compression piston rings.
- Burning conditions air-fuel mixture are far from favorable. Carbon deposits are heavily deposited in chambers, valve plates and piston crowns. During operation, this soot heats up and ignites the fuel without a spark at the spark plug (knock effect).
- If you need to sharply increase the engine speed while driving from the very bottom, you press the accelerator, but acceleration remains sluggish until the engine reaches its torque. But as soon as that happens, you shift into high gear and the crankshaft speed drops again. The load is large, there is not enough lubrication, the pump does not pump enough 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 not completely burned out, which means it is wasted.
For car owners equipped with on-board computer, it is easy to be convinced of uneconomic movement "in tightness". It is enough to turn on the display of the instantaneous fuel consumption on the display.
Such a driving style strongly wears out the power unit when the car is operated in difficult conditions - on dirt and country roads, fully loaded or with a trailer. Owners of cars with powerful motors volume of 3 liters or more, capable of sharply accelerating from the bottom. Indeed, 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 manner of driving "slipper to the floor" implies constant unwinding of the crankshaft up to 5-8 thousand revolutions per minute and later gearshifts, when the noise of the engine literally rings in your ears. What this driving style is fraught with, except for creating emergency situations on road:
- all components and assemblies of the car, and not only the engine, experience maximum loads during the service life, which reduces the total resource by 15–20%;
- due to intense engine heating, the slightest failure of the cooling system leads to overhaul due to overheating;
- exhaust pipes burn out much faster, and with them - an expensive catalyst;
- transmission elements wear out;
- since the crankshaft rotation speed exceeds the normal rpm, if not double, the fuel consumption also doubles.
Exploitation of the vehicle has an additional negative effect related to quality road surface... Movement on high speed on uneven roads literally kills suspension elements, and in the shortest possible time. It is enough to fly the wheel into a deep pothole and the A-pillar will bend or crack.
How to drive correctly?
If you are not a race car driver and not an adherent of pull-back 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 get:
- The mileage before the overhaul of the engine will increase (the full resource depends on the brand of the car and the power of the engine).
- By optimizing the combustion of the air / fuel mixture, you can save fuel.
- Fast acceleration is available at any time, as soon as you press the accelerator pedal. If the revolutions are not enough, shift down on the move. Repeat the same steps when driving uphill.
- The cooling system will function in working mode and will save the power unit from overheating.
- Accordingly, the suspension and transmission elements will last longer.
Recommendation. Most modern carsequipped with high-speed gasoline engines, it is better to switch gears when reaching the threshold of 3000 ± 200 rpm. This also applies to the transition from high to low speed.
As stated above, dashboards cars do not always have tachometers. For drivers with a short 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 indicates the optimal engine speed in relation to the speed in different gears.
| 5-speed gearbox position | 1 | 2 | 3 | 4 | 5 |
| Optimum crankshaft rotation speed, rpm | 3200–4000 | 3500–4000 | not less than 3000 | > 2700 | > 2500 |
| Approximate vehicle speed, km / h | 0–20 | 20–40 | 40–70 | 70–90 | more than 90 |
Note. Considering that different brands and modifications of machines have different correspondence between the speed of movement and the number of revolutions, the table shows averaged indicators.
A few words about coasting from a mountain or after acceleration. Any fuel supply system has a forced idle move, activated in 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 petrol to the cylinders is blocked. So you can safely brake the engine on top speedwithout being afraid to waste fuel.
Almost every driver is well aware that the resource of the engine and other vehicle components directly depends on the individual driving style. For this reason, many car owners, especially beginners, often think about which revs are best to drive. Next, we will consider what engine speed you need to keep taking into account different road conditions during the operation of the vehicle.
Read in this article
Engine resource and revolutions while driving
Let's start with the fact that competent operation and constant maintenance optimal speed engine allows you to increase the service life. In other words, there are modes of operation 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 "regulate" this parameter... Note that this topic is the subject of discussion and controversy. More specifically, drivers are divided into three main groups:
- the first are those who operate the engine at low speeds, constantly moving "vnatyag".
- the second should include those drivers who only periodically spin their engine up to above average rpm;
- the third group is considered to be car owners who constantly maintain the power unit in a mode above average and high engine speeds, often driving the tachometer needle into the red zone.
Let's understand in more detail. Let's start with a low-end ride. This mode means that the driver does not raise the revs above 2.5 thousand rpm. on gasoline engines and holds about 1100-1200 rpm. on diesel. This driving style has been imposed on many since the days of driving schools. Instructors authoritatively argue that it is necessary to drive at the lowest rpm, since in this mode the greatest fuel economy is achieved, the engine is least loaded, etc.
Note that during 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 revs in this case are inextricably linked with driving at low speeds. There is logic in this, since a slow and measured movement allows you to quickly learn how to drive without jerks when changing gears on cars with manual transmissions, teaches a novice driver to move in a calm and smooth mode, provides more confident control over the car, etc.
Obviously, after receiving driving license This driving style is further actively practiced in your own car, growing into a habit. Drivers of this type start to get nervous when the sound of a spinning engine starts to be heard in the cabin. They think that an 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, rpm, say, at around 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 opportunity to accelerate dramatically without switching to downshift, especially on "".
- after changing the topography of the road, for example, on inclines, the driver does not downshift. Instead of shifting, he simply pushes harder on the gas pedal.
In the first case, the motor is often outside the "shelf", which does not allow the car to be quickly accelerated if necessary. As a result, this driving style affects overall driving safety. The second point directly affects the engine. First of all, driving at low revs under load with a strongly pressed gas pedal leads to detonation of the engine. The indicated detonation literally breaks the power unit from the inside.
In terms of consumption, the savings are virtually nonexistent, as pressing the accelerator pedal harder in an overdrive under load increases the air / fuel mixture. As a result, fuel consumption increases.
Also driving "vnatyag" 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 pressure it creates engine oil in from all the same engine speed. In other words, sleeve bearings are designed to operate under hydrodynamic lubrication. This mode involves supplying oil under pressure to the gaps between the liners and the shaft. This creates the desired oil film, which prevents wear of the mating elements. The efficiency of hydrodynamic lubrication is directly dependent on the engine speed, that is, the more revolutions, the higher the oil pressure. It turns out that with a high load on the engine, given the low speed, there is a high risk of severe wear and damage to the liners.
Another argument against driving at low revs is the reinforced engine. In simple words, as the speed rises, the load on the internal combustion engine increases and the temperature in the cylinders rises significantly. As a result, part of the carbon deposit simply burns out, which does not happen with constant operation at the bottom.
High engine speed
Well, you say, the answer is obvious. The engine needs to be spinned harder, since the car will confidently respond to the gas pedal, it is 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 revs also has its drawbacks.
High revs can be considered those that exceed the approximate figure of about 70% of the total available for a gasoline engine. The situation is slightly different, since units of this type are initially less revolving, but have a higher torque. It turns out high turnover for motors of this type, those that are located behind the "shelf" of the diesel torque can be considered.
Now about the engine resource for this driving style. Strong cranking of the engine means that the load on all its parts and the lubrication system increases significantly. The temperature indicator also increases, additionally loading. The result is increased engine wear and increased risk of engine overheating.
It should also be borne in mind that at high speed modes, the requirements for the quality of engine oil increase. Lubricant should provide reliable protection, that is, meet the declared characteristics of viscosity, oil film stability, etc.
Ignoring this statement leads to the fact that the channels of the lubrication system can clog with constant driving at high speeds. This happens especially often when using cheap semi-synthetics or mineral oil... The fact is that many drivers change oil not earlier, but strictly according to the regulations or even later than this period. The result is the destruction of the liners, disrupting the operation of the crankshaft, and other loaded elements.
What rpm are considered optimal for the motor
To preserve the engine's resource, it is best to drive at such speeds, which can be conventionally considered average and slightly above average. For example, if the "green" zone on the tachometer assumes 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 are trying to fit the torque shelf precisely 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 is from 30 to 70% of maximum number revolutions while driving. Under such conditions power unit minimal damage is done.
Finally, we add that from time to time it is advisable to spin up a well-heated and serviceable motor with quality oil 80-90% when driving on flat road... In this mode, it will be enough to drive 10-15 km. Note that this action does not need to be repeated often.
Experienced car enthusiasts recommend turning 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.
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Adjusting idle speed on the carburetor and injection engine. Features of the XX carburetor adjustment, idle speed adjustment on the injector.
DIY chainsaw carburetor setting
For an independent carburetor option, you must familiarize yourself with its device and understand the procedure for the work that is carried out to adjust the parts responsible for the correct functioning component parts device and nearby parts.
It is necessary to carefully handle the items for the system option, and also to determine whether the set characteristics correspond to very permissible values.
About the carburetor device
The carburetor serves to mix the combustible consistency with air, while observing the proportions established in advance. If clear doses are not followed, the proper operation of the motor is at risk. When a huge amount of air enters during mixing of a component, and there is not enough fuel, then such a mixture is considered "poor".
Over-saturation should not be allowed, because with a large amount of fuel compared to air, malfunctions or engine wear are also likely. Adjustment of the carburetor is needed not only before the initial introduction, but also when any differences in its operation are revealed. Before starting work with the chainsaw, do not forget to run it in.
Components of the carburetor
The carburetor design contains standard set parts, but may vary slightly depending on the manufacturer. Components:
- The foundation... It is a special tube that visually resembles an aerodynamic structure. Air passes through it. In the transverse direction in the middle of the pipe there is a damper. Its position can be changed. The more it is pushed into the passage, the less air enters the engine.
- Diffuser... This is the tapered part of the tube. With its help, the air flow rate increases exactly in the segment from which the fuel comes out.
- Channels for fuel supply. Fuel mixture contained in the float chamber, then passes into the nozzle, from which it flows into the sprayer.
- Float chamber... It is a separate structural element, reminiscent of the shape of a tank. Designed to constantly maintain the optimal level of the fuel fluid in front of the inlet to the air channel.
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What you need to have to set up
Every carburetor owner must have necessary tools to adjust this system. There are three adjusting screws located on the body of the device. They have their own markings:
- L - screw for low rpm correction.
- H - screw for high speed adjustment.
- T - regulates the idle speed, in most cases it is used for experiments.
Chainsaw air filter
Before adjusting the carburetor, you need to prepare the device:
- The engine warms up, that is, it starts about 10 minutes before the repair, and turns off when you start work (see how to start the chainsaw).
- The air filter is checked and washed.
- The chain is stopped by turning the screw T as far as it will go (see chain oil).
To carry out a safe repair, you need to prepare a flat surface where you can carefully position the device, and turn the chain in the opposite direction. We need a tachometer. It determines the presence of a malfunction in the carburetor. When the screws are turning, the sound should be perfect and absolutely even. If squealing notes are noticed, then the mixture is oversaturated.
Setting instructions
Carburetor adjustment is divided into two main steps. The first is called basic. It is performed with the engine running. The second is performed when the engine is warm.
To carry out the carburetor tuning procedure successfully, you need to read the operating instructions in advance specific model to identify additional features device settings.
First stage
The adjusting screws for the highest and lowest speed should be moved clockwise until the highest resistance is encountered. When the screws reach the stop, you need to translate them into back side and leave after passing 1.5 turns.
The main stage
Chainsaw STIHL 180 checking how many turns
In this video we will answer the question of how to tune or adjust the carburetor chainsaw do it yourself
Chainsaw STIHL 230 checking how many turns
Carburetor adjustment chainsaw DIY Champion 254. Initial carburetor adjustment shown
The engine turns on at medium speed and warms up like this for about 10 minutes. The screw responsible for adjusting the idle speed must move clockwise. It is released only when the engine comes into stable operation. It is necessary to check that the chain does not move during this process.
In idle mode, the engine may stall (the reason is here). In this case, immediately turn the adjusting screw clockwise until it stops. Sometimes the chain starts to move. In this case, turn the adjusting screw in the opposite direction.
Checking acceleration work
A little research needs to be done. Device acceleration is initiated. The serviceability of the engine should be assessed during the maximum revolutions. When the engine is functioning properly it means when you press the accelerator, the speed quickly increases to 15,000 rpm.
If this does not happen or the increase in speed is too slow, you must use the screw marked with the letter L. It turns counterclockwise. Moderate movements must be observed, since the turn cannot be more than 1/8 of a full circle.
Maximum number of revolutions
To limit this figure, you need to use a screw marked H. To increase the number of revolutions, turn it clockwise, and to decrease them in the opposite direction. The maximum frequency should not exceed 15000 rpm.
If you increase this indicator, the engine of the device will work for wear, which will lead to problems in the ignition system. When turning this screw, the ignition processes of the device must be taken into account. If the slightest glitches appear, then the maximum value of the revolutions must be reduced.
Final check at idle speed
Before this procedure, it is necessary to make a full adjustment of the components of the carburetor when operating at maximum speed. Next, you should check the functioning of the device in idle cold mode. When the correct parameters are reached during the adjustment, you can see the exact conformity of the carburetor design to the following criteria:
- When the idle cold mode is connected, the chain does not move.
Chainsaw accelerator
- When the accelerator is pressed even slightly, the engine revs up at an accelerated pace. With a gradual deepening of the pressure, it can be seen that the engine speed increases commensurately, reaching the maximum allowable values.
- When the engine is running, you can compare its sound to a four-stroke instrument.
If violations are noticed in the above parameters or the device was not adjusted in in full, you need to perform the main configuration step again. Sometimes actions are performed incorrectly. In this case, the device may fail due to the loss of the correct node settings. In this case, you will have to contact a specialist.
Dismantling the carburetor when it is necessary to check or repair components
Device different models carburetors are almost the same, so when working with them, you can use the standard scheme. All elements must be removed carefully, and then lay out in the order belowso that you can successfully place items in place at the end of the repair work.
Read:
Removing the top cover
- The top cover is removed. To do this, unscrew the 3 bolts holding it in a circle.
- The foam rubber is also removed, since it is the top part of filter that conducts air.
- The fuel hose is removed.
- The drive thrust is output directly to it.
- The cable end is disconnected.
- The petrol hose can be removed completely by pulling it off the fitting in a planned manner.
To finally prepare the carburetor for overhaul or replacement of the smallest parts, you need to carefully disconnect it from the main system... Sometimes further disassembly is required. Unscrew the components carefully and stack the fasteners in groups, as these small parts are easily lost.
Instruction for Chinese
To properly configure the carburetor of a Chinese chainsaw, you must first remember the factory settings of the device, then turn on the engine. Subsequently, you will have to leave it to work for several hours in order to accurately set your own parameters. Sometimes the work is performed once after ten minutes of engine operation, but many Chinese-made models require special handling.
Chinese Chainsaw Model
Adjustment procedure:
- Activities start in idle mode... With the help of the adjusting screws, you need to achieve a systematic set of revolutions by the engine, therefore, you should first let it run at low speeds. The deviation from the norm is the movement of the chain along the tire. In this case, you need to adjust the extreme screws to the optimal position so that the chain remains stationary.
- Transition to average speed... Sometimes the engine will smoke. This defect can be eliminated by tightening the screw to supply a leaner fuel mixture.
In this case, the smoke will disappear, but the engine speed will increase. It is necessary to adjust the settings until the level is reached when, when you press the throttle, the engine smoothly picks up speed, no sudden jerks or interruptions are heard.
Selecting the correct camshaft should start with two important decisions:
First, let's check how we define the operating RPM range and how the choice of camshaft is determined by that choice. The maximum engine rpm is usually easy to isolate as it directly affects reliability, particularly when the main parts of the block are common.
Maximum engine speed and reliability for most engines
| Maximum engine speed | Estimated working conditions | Life Expectancy with Corresponding Parts |
| 4500/5000 | Normal movement | More than 160,000 km |
| 5500/6000 | "Soft" forcing | More than 160,000 km |
| 6000/6500 | Approximately 120,000-160,000 km | |
| 6200/7000 | Forcing for everyday driving / "soft" racing | About 80,000 km |
| 6500/7500 | Very "hard" street driving or racing from "soft" to "hard" | Less than 80,000 km in street driving |
| 7000/8000 | Only "hard" races | Approximately 50-100 rides |
Keep in mind that these guidelines are general. One engine can hold up much better than another in any category. How often the engine accelerates to maximum rpm is also very important. However, as general rule you need to be guided by the following: maximum speed engine must be below 6500 rpm if you are building a high-powered engine for everyday driving and you want reliable operation. These engine speeds are typical for the limits of most parts and can be obtained with medium force valve springs. Therefore, if reliability is the main goal, then the maximum speed of 6000/6500 rpm will be a practical limit. While deciding the maximum RPM required can be a relatively straightforward process, based in principle on reliability (and perhaps cost), an inexperienced engine designer may find it much more difficult and dangerous to determine the engine's operating speed range. Valve lift, cycle times and cam profile camshaft will determine the power range, and some inexperienced mechanics may be tempted to choose the “largest” camshaft possible in an attempt to increase the maximum engine power. However, it is important to know that maximum power is only needed for a short time, when the engine reaches maximum rpm. The power required from most high-powered engines is well below maximum power and rpm; in fact, a typical boosted engine may "see" full opening throttle just a few minutes or seconds in a full day of work. However, some inexperienced engine builders ignore this obvious fact and choose a camshaft by intuition rather than guided? If you suppress your desires and make careful choices based on real facts and possibilities, then you can create an engine capable of delivering impressive power. Always keep in mind that the camshaft is pretty much a compromise piece. After a certain point, all the increases come at the cost of power at low rpm, loss of throttle response, economy, etc. If your goal is to increase the number of horsepower, then first make modifications that add maximum power by improving intake efficiency, since these changes have less effect on power at low revs. For example, optimize the flow in the cylinder head and in the exhaust system, reduce the flow resistance in the intake manifold and in the carburetor, then install the camshaft in addition to all of the above "kit". If you use these techniques carefully, the engine will deliver the broader power curve possible for your investment of time and money.
In conclusion, if you have a car with automatic transmission, then you need to be conservative when choosing the valve timing of your camshaft. Excessive valve opening times will limit engine power and torque at low rpm, which are essential elements in good acceleration and pulling away. If your vehicle's torque converter (converter) stops at 1500 rpm (typical for many standard transmissions), a camshaft that delivers good torque, although not necessarily maximum power, at 1500 rpm will accelerate well. You may be tempted to use a torque converter with a high stop rpm and a camshaft with a long opening time in an attempt to achieve better result... However, if you use one of these torque converters during normal driving, their efficiency at low revs will be very poor. Fuel efficiency will suffer quite a lot. For a car in everyday use, there are better ways to improve acceleration from low revs.
Let's summarize the main elements of camshaft selection. First, for day-to-day driving, the maximum engine speed must be maintained at no more than 6500 rpm. Above this limit will significantly reduce engine life and increase component costs. While a "conventional" engine may benefit from as much valve lift as possible, too much valve lift will reduce engine reliability. For all high-lift camshafts, bronze valve guides are essential to ensure long bushing life, but for valve lift of 14.0 mm or more, even bronze guide bushings cannot reduce wear to a level acceptable for normal applications.
The longer the valves are held open, especially inlet valve, the more maximum power the engine will deliver. However, due to the variable nature of the camshaft timing, if the duration of valve opening or valve overlap goes beyond a certain value, all the additional maximum power will be gained at the expense of quality at low rpm. Camshafts with an intake stroke of up to 2700, measured at zero valve lift, are a good replacement for standard camshafts. For high-performance engines, the upper limit for intake stroke times over 2950 is a pure racing engine's accessory.
Valve overlap causes some torque loss at low rpm, however, this loss is reduced when overlap is carefully selected for a particular application - from about 400 for standard engine camshafts to 750 or more for special applications.
Valve opening times, valve overlap, valve timing and cam center angles are all related. It is not possible to set each of these characteristics independently on engines with one camshaft.
Fortunately, most camshaft technicians have spent many years creating cam profiles for power and reliability, so they can offer a camshaft that suits your needs well. However, do not blindly take what the masters are offering you; you now have the information you need to competently discuss the specifics of the camshafts with their manufacturers.
After all, the camshaft is one part of the intake system. It should be matched with the cylinder head, intake manifold and exhaust system. Volume intake manifold and the exhaust manifold pipes must be sized to fit the engine power curve. In addition to this, carburetor air flow rate, number of chambers, type of secondary chamber activation, etc. also have a noticeable effect on power.
