A camshaft is a rod that rotates and slides against a bit of machinery to show rotational motion into linear motion. This variation of motion is accomplished by the camshaft moving further and closer from the axis of rotation because the camshaft is pushed by the machinery. These moving pieces of the shaft are the cams. The linear distance moved is termed the ‘throw’.
A camshaft on an enclosed combustion engine is a device that controls both the input of fuel and therefore the expulsion of gas. It consists of several radial cams, each displacing intake or exhaust valves. This camshaft is connected to the crankshaft via belt, chain, or gears. This ensures consistent timing of the valves concerning the motion of the pistons.
The function of a camshaft relies on how a valve works and therefore the function of the cam itself. A valve on a plate consists of two basic parts, a stem, and an ahead. The top plugs the nozzle that enables fuel intake or exhaust flow and requires linear motion.
Since an automotive engine has several pistons, a single-cam is insufficient for all of those pistons. a whole rod covered with cams must be used. This is often the camshaft. Note that the precise placement of the cams along the shaft allows for the precise timing of the opening and shutting of the relative valve. This precise timing is required since a car engine is firing at thousands of RPM.
What Does a Camshaft Do?
This is what a Camshaft does:
The camshaft is critical to the fundamental function of an engine. Comprised of two distinct parts, the cams, and also the shaft, the camshaft is that the element that allows valves to open. Because the shaft rotates, the egg-shaped cams (or “lobes”) push the valves open in sync with the crankshaft gear.
In modern overhead-cam (OHC) engines, the camshaft is found within the cylinder head. Single OHC (SOHC) engines have one cam per bank, usually mounted between the valve stems. Rocker arms transmit SOHC movement to the valves. Dual OHC (DOHC) engines have two cams per bank, usually directly over the valve stems, one for intake valves and one for exhaust valves. Force is transmitted on to the valve.
An i4 (four-cylinder) SOHC engine has one camshaft, while a V6 or V8 SOHC engine has two. An i4 DOHC engine has two camshafts, while a V6 or V8 DOHC engine has four camshafts. Overhead-cam engines have three to 5 valves per cylinder, but usually two intake valves and two exhaust valves.
Older engines and some newer “pushrod” engines have one camshaft within the engine block. Long metal pushrods transmit camshaft movement to the rocker arms, which transmit that movement to the valves. Pushrod engines usually have two or three valves per cylinder, usually one valve and one valve.
The typical camshaft is milled from a rough-formed cast steel blank. Some performance and custom camshafts are also milled from a solid steel block.
How Camshafts Works?
As the camshaft rotates, the cam lobes move up and down. In DOHC engines, every rotation causes one cam lobe to push the valve down, opening it into the cylinder. Similarly, in SOHC and pushrod engines, the cam lobe pushes on the rocker arms (or pushrods then rocker arms), opening the valve. Because the cam lobe rotates further, the valve spring forces the valve to make a copy, closing it.
The camshaft is sometimes connected to the crankshaft employing a timing chain or timing belt. In some pushrod engines, timing gears may additionally be used. The camshaft gear has twice as many teeth because the crankshaft gear, which allows it to rotate at half the speed of the crankshaft. The camshaft has four distinct strokes: intake, compression, power, and exhaust.
Common camshafts are made to match typical operating characteristics and will accentuate highway cruising efficiency or low-end power. Similarly, valve “lift” refers to the peak of the lobe about the middle of the shaft, which determines how far the valve opens. On fixed camshafts, this can be not adjustable, but there are circumstances at which the engine might “breathe” better if only the valves could open a touch more.
Also, a hard and fast camshaft might open the valve 10° before TDC (BTDC) and shut it 5° after bottom spatial relation (ABDC) and open the valve 15° before bottom spatial relation (BBDC) and shut it 5° ATDC. This is often cited as valve opening duration. This works well on average but doesn’t excel in anyone’s driving situation.
What are the Specialized Camshaft Functions?
Specialized Camshaft Functions:
Timing is vital. Valves must open and shut at specific intervals concerning cylinder position. As an example, as the cylinder is coming to the highest dead center (TDC) on the exhaust stroke, the camshaft is opening the intake valves and shutting the exhaust valves. At the identical time, the cylinder may be reaching TDC on the compression stroke, therefore the camshaft would go away those valves closed.
Camshafts fitted with variable valve timing (VVT) use hydraulic actuators to advance or retard valve timing about the crankshaft angle. VVT enables high-speed efficiency or low-speed power.
Using specialized variable valve lift (VVL) camshafts and computer-controlled solenoids or hydraulic actuators, the ECM can select between two valve lift options, looking at driver demand.
On vehicles with a direct mechanical system, some diesel engines, and most gasoline direct injection engines, the high-pressure fuel pump (HPFP) is driven by a lobe on one amongst the camshafts.
What are the Common Camshaft Problems?
Common Camshaft Problems:
The camshaft is a solid steel component, it isn’t susceptible to wear or breakage. In most engines, other parts will wear out before the camshaft. Still, some common camshaft problems may arise.
Worn Cam Lobes (also called “wiped out” or “flogged”);
This refers to cam lobes that are worn down. Worn cam lobes won’t open the valves the maximum amount as intended, resulting in poor engine performance and cylinder misfiring. If this affects the HPFP, insufficient fuel pressure will result in higher emissions and random misfiring.
They don’t confer with an exclusive camshaft problem but may be driven by the camshaft. A worn lifter won’t lift the valve the maximum amount as intended, if at all, and is often heard as a clattering or tapping within the valve cover.
It refers to the catastrophic failure of the camshaft. This might be a producing defect or be caused by the camshaft seizing. In pushrod engines, a broken camshaft could significantly damage connecting rods, engine block, pistons, or the crankshaft. In interference engines, a broken camshaft could damage the cylinder head, valves, or pistons.
All three of those problems are caused by the absence of proper engine maintenance. Prevent camshaft issues by getting regular engine oil changes with quality oil, adhering to manufacturer recommendations regarding car care interval, oil type, and oil viscosity, and avoiding engine overheating.
What are the key parts of a Camshaft?
Key Parts of a Camshaft:
The key parts of any camshaft are the lobes. Because the camshaft spins, the lobes open and shut the intake and exhaust valves in time with the motion of the piston. It seems that there’s a direct relationship between the form of the cam lobes and also the way the engine performs in several speed ranges.
To understand why this can be the case, imagine that we are running an engine extremely slowly — at just 10 or 20 revolutions per minute (RPM) — so that it takes the piston a pair of seconds to complete a cycle. It’d be impossible to truly run a standard engine this slowly, but let’s say that we could. At this slow speed, we’d want cam lobes shaped so that:
- Just as the piston starts moving downward in the intake stroke (called the highest spatial relation, or TDC), the valve would open. The valve would close right because the piston bottoms out.
- The valve would open right because the piston bottoms out (called bottom spatial relation, or BDC) at the top of the combustion stroke, and would close because the piston completes the exhaust stroke.
This setup would work very well for the engine as long because it ran at this very slow speed. But what happens if you increase the RPM? Let’s understand.
When RPM Increased:
When you increase the RPM, the ten to twenty RPM configuration for the camshaft doesn’t work well. If the engine is running at 4,000 RPM, the valves are opening and shutting 2,000 times every minute, or 33 times every second. At these speeds, the piston is moving very quickly, that the air/fuel mixture rushing into the cylinder is moving very quickly further.
When the valve opens and also the piston starts its intake stroke, the air/fuel mixture in the intake runner starts to accelerate into the cylinder. By the time the piston reaches the underside of its intake stroke, the air/fuel is moving at a reasonably high speed. If we were to slam the valve shut, all of that air/fuel would come to a stop and not enter the cylinder. By leaving the valve open a bit longer, the momentum of the fast-moving air/fuel continues to force air/fuel into the cylinder because the piston starts its compression stroke.
Therefore the faster the engine goes, the faster the air/fuel moves, and therefore the longer we wish the valve to remain open. We also want the valve to open wider at higher speeds — this parameter, called valve lift, is governed by the cam lobe profile.
What are the different engine arrangements of a Camshaft?
Different Engine Arrangments of a Camshaft:
There are some different arrangements of camshafts we found on engines. We’ll discuss a number of the foremost common ones. You’ve probably heard the terminology:
- Single overhead cam (SOHC): The oldest configuration of an overhead camshaft engine is that the single overhead camshaft (SOHC) design. A SOHC engine has one camshaft per bank of cylinders, therefore a straight engine has a complete of 1 camshaft. A V or flat engine with a complete of two camshafts (one per bank of cylinders) could be a single overhead camshaft engine, not a double overhead camshaft engine.
- Double overhead cam (DOHC): A double overhead camshaft or dual overhead camshaft (DOHC or “twin-cam”) engine has two camshafts per bank of the plate, one for the intake valves and also the other for the exhaust valves. Therefore there are two camshafts for a straight engine and a complete of 4 camshafts for a V engine or a flat engine.
- Pushrod: An overhead camshaft or OHC engine has overhead valves; but, not to be confused, Overhead valve engines that use pushrods are often called “pushrod engines”. Some early “intake over exhaust” engines used a hybrid design combining elements of both side-valves and overhead valves.
What is a SOHC Arrangement?
Single OverHead Cam:
This arrangement denotes an engine with one cam per head. So if it’s an inline 4-cylinder or inline 6-cylinder engine, it’ll have one cam; if it’s a V-6 or V-8, it’ll have two cams (one for every head).
The cam actuates rocker arms that move on the valves, opening them. Springs return the valves to their closed position. These springs need to be very strong because at high engine speeds, the valves are pushed down very quickly, and it’s the springs that keep the valves in grips with the rocker arms. If the springs weren’t strong enough, the valves might come off from the rocker arms and snapback. This is often an undesirable situation that might lead to extra go down the cams and rocker arms.
A single overhead cam:
On single and double overhead cam engines, the cams are driven by the crankshaft, via either a belt or chain called the timing belt or timing chain. These belts and chains have to get replaced or adjusted at regular intervals. If a timing belt breaks, the cam will stop spinning and therefore the piston could hit the open valves.
What is a DOHC Arrangement?
Double OverHead Cam:
A double overhead cam engine has two cams per head. So inline engines have two cams, and V engines have four. Usually, double-overhead cams are used on engines with four or more valves per cylinder — one camshaft simply cannot fit enough cam lobes to actuate all of these valves.
The main reason to use double overhead cams is to permit more intake and exhaust valves. More valves mean that intake and exhaust gases can flow more freely because there are more openings for them to flow through. This increases the power of the engine.
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