Sikander Safary

HIIT stands for High Intensity Interval Training and has become a popular workout method due to its efficiency and effectiveness. Combined

N-version programming, also known as multiversion programming or multiple-version dissimilar software, is a method or process in software engineering where multiple functionally equivalent programs are independently generated from the same initial specifications.

Cost-based transfer prices. •Transfer price is based on the costs of producing the intermediate product. Examples include: - Variable production costs.

This page undergoes regular review and was last comprehensively reviewed on February 7, 2023. Some sections may reflect more recent updates.

The four COVID-19 vaccines available for use in the U.S. follow various dosing schedules. All four vaccines have been demonstrated to be highly effective against severe outcomes related to COVID-19 in clinical trials and postauthorization observational studies. However, given concerns about waning immunity and the emergence of novel variants, there is interest in understanding the potential role of alternative dosing strategies for these vaccines to augment or prolong their protective effect, including (but not limited to) administration of additional doses of each vaccine, schedules containing different products (“mix and match”) and modified dosing intervals.

Although individuals may receive the second dose in the primary series at extended intervals, shorter intervals are still recommended for moderately to severely immunocompromised individuals, adults aged 65 and older and others who need rapid protection. The very small risk of myocarditis, especially for males aged 12-39 years, may be further reduced with an extended interval between primary doses.

*Children and adults aged 6 years or older can receive a Pfizer-BioNTech or a Moderna bivalent booster, regardless of what they received in the primary series. Children aged 5 years who received a Moderna primary series can receive a Pfizer-BioNTech or a Moderna bivalent booster. Children aged 5 years who received a Pfizer-BioNTech primary series should receive a Pfizer-BioNTech bivalent booster.

‡Children aged 6 months to 4 years who received a Moderna primary series should only receive a Moderna bivalent dose as a booster.

§Patients aged 18 years and older who completed a primary series of any COVID-19 vaccines and have not received any previous booster dose(s) may receive a monovalent Novavax booster dose at least 6 months after completion of their primary series, if they are not able or not willing to receive an mRNA vaccine and would otherwise not receive a booster dose.

**Individuals who previously received J&J/Janssen vaccine, which is no longer recommended, may receive a single bivalent mRNA booster dose.

*Children and adults aged 6 years or older can receive a Pfizer-BioNTech or a Moderna bivalent booster, regardless of what they received in the primary series. Children aged 5 years who received a Moderna primary series can receive a Pfizer-BioNTech or a Moderna bivalent booster. Children aged 5 years who received a Pfizer-BioNTech primary series should receive a Pfizer-BioNTech bivalent booster.

‡People aged 18 years and older who have completed any COVID-19 vaccine primary series and who have not received any booster dose(s) may receive a monovalent Novavax booster dose at least 6 months after completion of the primary series, if they are unwilling or unable to receive an mRNA vaccine and would otherwise not receive a booster dose.

**Individuals who previously received J&J/Janssen vaccine, which is no longer recommended, may receive a single bivalent mRNA booster dose.

For individuals receiving a Moderna, Pfizer-BioNTech or J&J/Janssen primary series who are moderately to severely immunocompromised, the U.S. recommends a routine additional dose of mRNA vaccine as part of the primary series. This equates to a third mRNA vaccine dose in the primary series for those who received Pfizer-BioNTech or Moderna; for individuals with a single-dose J&J/Janssen primary series, this equates to a second vaccine dose in the primary series. Moderately or severely immunocompromised individuals who receive Novavax as the primary series are now recommended to receive a bivalent booster at least 2 months after completion of the primary series.

FDA has authorized and CDC recommends an additional dose of COVID-19 mRNA vaccine as part of the primary series for certain immunocompromised populations.

Key primary studies that have evaluated the effect of additional doses of COVID-19 vaccines as part of a primary series in immunocompromised populations include:

There is no current recommendation to offer a third dose of COVID-19 vaccine as part of the primary series to immunocompetent adults. There are limited data on the effect of a third dose used in this context. However, the emergency use authorization of Pfizer-BioNTech vaccine in children 6 months-4 years has a third dose included in the primary series. The third dose was added to the primary series after immunobridging success criteria were not met for this age group with only two primary series vaccine doses.

In the U.S., CDC recommends everyone ages 5 years and older receive one updated bivalent mRNA COVID-19 vaccine booster dose after completing their mRNA, viral vector or recombinant subunit primary COVID-19 vaccination series. Children who are 5 years old are only recommended to receive the Pfizer-BioNTech bivalent booster; children 6 years old and older can receive either Pfizer-BioNTech or Moderna bivalent booster. All bivalent boosters should be received at least 2 months after completion after the primary series, or at least 2 months after the last monovalent booster dose.

Bivalent mRNA vaccines contain both a vaccine antigen against the ancestral strain of SARS-CoV-2 as well as an antigen against BA.4/BA.5 Omicron subvariants. These bivalent vaccines have the same total antigen amount as adult monovalent vaccines (i.e., in the U.S., Moderna bivalent vaccine contains 25 mcg of spike protein from ancestral SARS-CoV-2 and 25 mcg of spike protein from Omicron (BA.4/BA.5) SARS-CoV-2, whereas primary series doses each contain 50mcg of spike protein from ancestral SARS-CoV-2; Pfizer bivalent vaccine contains 15 mcg of spike protein from each antigen, whereas primary series doses each contain 30mcg of spike protein from the ancestral strain only). Bivalent boosters should be administered without regard to the number of previous monovalent booster doses received. CDC suggests that where possible, booster vaccines to be received should “match” the vaccines received in the primary series (e.g., individuals receiving Moderna primary series vaccines should, where possible, receive a Moderna bivalent booster).

Individuals should only receive one bivalent booster dose. CDC recommends all booster doses be bivalent mRNA vaccines (regardless of the vaccine type received for primary series). An analysis of safety data gathered through the v-safe surveillance system found that booster doses were safe overall and associated with fewer reactogenicity events than second doses of mRNA vaccine (Hause, February 2022). However, individuals aged 18 years and older who are unable to receive a bivalent mRNA booster, or who refuse to receive a bivalent mRNA booster, may receive a Novavax booster starting 6 months after primary series completion.

Booster doses augment immune responses (quantitatively or qualitatively) against SARS-CoV-2 (and relevant variants).

Data for augmented immune responses following booster doses come from several studies. In a substudy of the Phase 1 clinical trial of the Pfizer-BioNTech COVID-19 vaccine, 23 participants received a booster dose of the vaccine at approximately 8 months after completion of the primary series. One month after the booster dose, neutralizing antibody titers against both wildtype virus and the Beta (B.1.351) and Delta (B.1.617.2) variants had increased to levels higher than at 1 month after the primary series (Falsey, September 2021). In another study of 97 Israeli healthcare workers aged ≥60 years who received a third dose of the Pfizer-BioNTech COVID-19 vaccine approximately 6-7 months after their primary series, the additional vaccine dose significantly increased anti-spike IgG antibody titers measured 10-19 days after vaccination (Eliakim-Raz, November 2021).

The two largest studies were multicenter studies that compared the safety and immunogenicity of a variety of different booster vaccines, including heterologous doses. In an interim analysis of a multicenter trial conducted at 10 sites in the U.S., the investigators reported immune responses following heterologous and homologous booster doses among >400 participants who had previously been vaccinated with either two doses of an mRNA COVID-19 vaccine or one dose of the Johnson & Johnson/Janssen COVID-19 vaccine (at least 12 weeks earlier). In this study, a booster dose with any product augmented antibody concentrations, but heterologous boosts (“mixed” regimens) elicited a more robust response than homologous boosts (“matched” regimens) (Atmar, January 2022).

In another large study conducted in the U.K., the investigators reported immune responses following heterologous and homologous boosters among >2800 participants who had previously received either two doses of the Oxford-AstraZeneca or Pfizer-BioNTech COVID-19 vaccine (at least 10-12 weeks earlier). Participants were randomized to receive boosts with the Oxford-AstraZeneca, Pfizer-BioNTech, Moderna or Johnson & Johnson/Janssen COVID-19 vaccines, as well as the Novavax COVID-19 vaccine, the CureVac mRNA COVID-19 vaccine and an inactivated vaccine. All the booster vaccines augmented immune responses following a Pfizer-BioNTech COVID-19 vaccine series, with the two currently authorized mRNA COVID-19 vaccines demonstrating the greatest effect (Munro, December 2021).

Limitations

The durability of these augmented immune responses is unknown. In a longitudinal study of immune responses to SARS-CoV-2 following mRNA COVID-19 vaccination (mostly the Pfizer-BioNTech COVID-19 vaccine), the investigators separately analyzed the kinetics of the immune response in individuals with and without prior SARS-CoV-2 infection. For those with prior infection, the primary vaccine series may already be considered a “booster.” In this group, antibody, memory B cell and T cell responses were augmented by vaccination but had declined nearly back to baseline by 6 months (Goel, October 2021).

Booster doses lead to increased vaccine effectiveness against COVID-19.

Multiple studies have evaluated the clinical effectiveness of a COVID-19 vaccine booster dose. These are mostly observational cohort studies during time periods when either Delta or Omicron were the predominant circulating variants. Together, the data indicate that a booster dose of an mRNA COVID-19 vaccine (i.e., a third dose given several months after a two-dose primary series) provides a significant protective effect against symptomatic COVID-19 (Bar-On, September 2021; Saciuk, November 2021; Patalon, November 2021; Bar-On, December 2021), COVID-19 hospitalization and death compared with two doses of vaccine (Barda, October 2021; Arbel, December 2021; Andrews, January 2022). Preliminary evidence suggests this may also be the case for NVX-CoV2373 when used as a booster after ChAdOx1 or BNT162b2 primary series (Munro, December 2021).

The emergence of the Omicron variant and its capacity for immune escape also motivated a number of studies to evaluate the benefits of booster doses. Booster doses of mRNA COVID-19 and the Johnson & Johnson/Janssen COVID-19 vaccines appear to restore in vitro neutralization titers (Nemet, December 2021; Garcia-Beltran, December 2021; Pajon, January 2022; Lyke, January 2022 – preprint, not peer-reviewed) as well as clinical effectiveness (Andrews, December 2021 – preprint, not peer-reviewed; Thompson, January 2022; Johnson, January 2022; Accorsi, January 2022; Gray, December 2021 – preprint, not peer-reviewed; Hui Xuan Tan, February 2022; Ferdinands, February 2022). As an example, in a non-peer-reviewed analysis of SARS-CoV-2 infections in the U.K. following the emergence of the Omicron variant, the authors found that two doses of the Pfizer-BioNTech COVID-19 vaccine demonstrated a vaccine effectiveness against symptomatic COVID-19 (presumed due to Omicron) of 88.0% (95% CI, 65.9-95.8%) 2-9 weeks after dose 2, 48.5% (95% CI, 24.3-65.0%) at 10-14 weeks post dose 2 and 34-37% from 15 weeks post dose 2; 2 weeks after a booster dose with the Pfizer COVID-19 vaccine, vaccine effectiveness had increased to 75.5% (95% CI, 56.1-86.3%) (Andrews, December 2021 – preprint, not peer-reviewed).

Limitations

The durability of this improvement in vaccine effectiveness is poorly characterized. In an analysis of urgent care encounters, emergent department visits and hospitalizations due to COVID-19 in the VISION Network in the U.S., investigators found waning effectiveness of third (booster) doses of mRNA COVID-19 vaccines against all three outcomes after 2 months, during both the Delta and Omicron waves. Notably, booster dose effectiveness waned more significantly against urgent care and emergency department encounters, but showed more durability against hospitalization, remaining greater than 75% for up to 4 months after vaccination during both time periods (Ferdinands, February 2022).

Bivalent booster doses likely provide additional protection against Omicron subvariants of SARS-CoV-2.

Preliminary safety and efficacy information presented at a Sept. 1, 2022 ACIP meeting suggest that the inclusion of a second SARS-CoV-2 variant antigen in mRNA vaccines broadens the overall antibody response to SARS-CoV-2. In presentations to ACIP, safety data about bivalent vaccines from approximately 1,400 individuals was presented. The information presented concerned bivalent vaccines, all of which included an antigen for the SARS-CoV-2 ancestral strain; some bivalent vaccines also included antigen for the BA.1 Omicron subvariant and others included antigen for BA.4/BA.5 Omicron subvariants. Overall, Omicron-specific bivalent booster vaccines resulted in higher anti-Omicron antibody and higher antibody titers for other SARS-CoV-2 variants. Modeling work presented at this meeting suggested that broad uptake of these updated bivalent vaccines in the early fall of 2022 could prevent a substantial number of hospitalizations.

In the U.S., CDC currently recommends completing a primary series of a two-dose vaccine (or three doses for certain immunocompromised patients) with the same product, whenever possible. For booster vaccination, FDA has authorized the use of heterologous (or “mix and match”) booster doses for currently available mRNA, recombinant subunit and viral vector COVID-19 vaccines. Interim CDC guidance addresses clinical considerations related to heterologous booster doses, including patient benefit-risk considerations when selecting which booster dose to receive.

Primary series

There have been few studies evaluating a mixed product primary series with the vaccines currently available in the U.S. The largest such study, the Com-COV2 trial, was conducted in the U.K. and compared the safety and immunogenicity of two doses of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines with heterologous schedules containing one dose of either followed by one dose of either the Moderna or Novavax COVID-19 vaccine (Stuart, December 2021). The safety and immunogenicity of a vaccine series containing two doses of the Pfizer-BioNTech vaccine were similar to a vaccine series containing one dose of Pfizer-BioNTech followed by one dose of Moderna. Antibody and cellular response were slightly higher in the mixed schedule group, which may be attributable to the higher antigen content in the Moderna vaccine rather than any benefit of a mixed schedule per se.

The Com-COV2 trial and other studies outside the U.S. have also evaluated mixed schedules containing one dose of an mRNA vaccine and one dose of the Oxford-AstraZeneca vaccine (which is based on a similar technology to the Johnson & Johnson/Janssen COVID-19 vaccine), though the time between the first and second dose of vaccine in these studies has been variable. Most of these studies have concluded that a two-dose schedule that includes both vaccines, in either order, generates a robust antibody and cellular response, compared with a single dose of either vaccine. Furthermore, in the studies where a heterologous and homologous (i.e., containing two doses of the same vaccine product) schedule were directly compared, the safety profile and immune responses with both schedules appeared to be similar (Borobia, June 2021; Shaw, May 2021; Liu, August 2021; Ostadgavahi, May 2021; Hillus, November 2021; Schmidt, September 2021; Tenbusch, July 2021; Dimeglio, August 2021). In some studies, a heterologous schedule containing one Oxford-AstraZeneca and one mRNA COVID-19 vaccine dose elicited a more robust cellular response and higher neutralizing antibody titers against SARS-CoV-2 variants than a homologous schedule containing two doses of the Oxford-AstraZeneca vaccine (Barros-Martins, July 2021; Kaku, February 2022).

Boosters

Some studies suggest that heterologous boosters may be superior to homologous boosters. Per CDC guidance, mRNA COVID-19 boosters are preferred over the Johnson & Johnson/Janssen COVID-19 vaccine. Data to support this recommendation come from studies on immunogenicity (Atmar, January 2022; Munro, December 2021; Sablerolles, January 2022) and clinical effectiveness (Mayr, February 2022; Hui Xuan Tan, February 2022).

The interval between doses of two-dose COVID-19 vaccines may impact their immunogenicity and clinical effectiveness. However, to date there are limited data for this strategy; therefore, alternative schedules are not currently recommended.

Key primary studies that have evaluated the effect of alternate COVID-19 vaccine schedules are summarized below.

There is accumulating evidence that a longer interval between the two doses of mRNA COVID-19 vaccines may confer improved immunogenicity and potentially even clinical effectiveness. Studies in the U.K. and Canada have demonstrated that a longer time period (ranging from 6-16 weeks depending on the study) between the two doses of both the Pfizer-BioNTech and Moderna COVID-19 vaccines is associated with increased antibody and cellular responses (Parry, August 2021; Grunau, November 2021; Grunau, December 2021; Payne, November 2021). A separate analysis in the U.K. of 750 adults aged 50-79 years confirmed these findings and further demonstrated that an interval of >45 days between dose one and two of the Pfizer-BioNTech COVID-19 vaccine was associated with improved vaccine effectiveness (over a follow-up period that preceded emergence of the Delta variant) against SARS-CoV-2 infection (Amirthalingam, December 2021).

In an exploratory analysis of a Phase 3 randomized controlled trial of the Oxford-AstraZeneca COVID-19 vaccine, investigators evaluated the impact of variable timing of the second dose of vaccine. In this analysis, vaccine efficacy against primary symptomatic COVID-19 (starting 14 days after the second dose) was higher with longer dose intervals. Vaccine efficacy was 55.1% (95% CI, 33.0-69.9) when the interval between the two doses was less than 6 weeks and 81.3% (60.3-91.2) when the interval was more than 12 weeks (Voysey, February 2021).

RPG Core Combat Creator: Learn Intermediate Unity C# Coding,Udemy.

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To download tutorial or watch: RPG Core Combat Creator: Learn Intermediate Unity C# Coding

Why this tutorial?

Udemy RPG Core Combat Creator: Learn Intermediate Unity C# Coding

Note: Build Combat for Role Playing Game (RPG) in Unity. Tutorials Cover Code Architecture & Video Game Design.. Ben Tristem is the instructor of this tutorials.

To download tutorial or watch: RPG Core Combat Creator: Learn Intermediate Unity C# Coding

Benefits from this tutorials

1. Create core combat mechanics for melee, ranged and special attacks.
3. More advanced C# techniques such as interfaces, delegates, and co-routines.
5. Create pathfinding systems and patrol paths for enemies and NPCs.
7. Make a detailed level with terrain, enemies, triggers, lighting, particles and props.
9. Balance the player and enemy stats (eg. health, damage, movement, attack speed, and more).
11. Advanced game design, project management and code architecture strategies.

To download tutorial or watch: RPG Core Combat Creator: Learn Intermediate Unity C# Coding

Video Tutorial Details

To download tutorial or watch: RPG Core Combat Creator: Learn Intermediate Unity C# Coding

Melbourne Business School continues to be the best of the 14 MBA programs from Australia and New Zealand in this year's ranking, despite a fall in its overall s

Benefits of fasting Experts have also found that restricting food intake during the day can help prevent health problems such as high

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After the voice prompt, say “setup” and then “phone pairing” Say “pair a phone,” then enter the four-digit PIN for your UConnect system (find this in your vehicle's manual) Say “yes” to confirm your PIN Give a name for your phone at the prompt, then assign a priority number

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Besides, it also contains a blood thinner, Clopidogrel, that prevents the formation of blood clots and also prevents the existing ones from growing bigger in size. Take it regularly and make appropriate lifestyle changes (such as eating healthy and staying active) to maximize the effectiveness of this medicine. Keep taking it even if you feel well.

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I’ve never been a car guy. I just didn’t have any interest in tooling around under the hood to figure out how my car works. Except for replacing my air filters or changing the oil every now and then, if I ever had a problem with my car, I’d just take it into the mechanic and when he came out to explain what was wrong, I nodded politely and pretended like I knew what he was talking about.

But lately I’ve had the itch to actually learn the basics of how cars work. I don’t plan on becoming a full on grease monkey, but I want to have a basic understanding of how everything in my car actually makes it go. At a minimum, this knowledge will allow me to have a clue about what the mechanic is talking about the next time I take my car in. Plus it seems to me that a man ought to be able to grasp the fundamentals of the technology he uses every day. When it comes to this website, I know about how coding and SEO works; it’s time for me to examine the more concrete things in my world, like what’s under the hood of my car.

I figure there are other grown men out there who are like me — men who aren’t car guys but are a little curious about how their vehicles work. So I plan on sharing what I’m learning in my own study and tinkering in an occasional series we’ll call Gearhead 101. The goal is to explain the very basics of how various parts in a car work and provide resources on where you can learn more on your own.

So without further ado, we’ll begin our first class of Gearhead 101 by explaining the ins and outs of the heart of a car: the internal combustion engine.

An internal combustion engine is called an “internal combustion engine” because fuel and air combust inside the engine to create the energy to move the pistons, which in turn move the car (we’ll show you how that happens in detail below).

Contrast that to an external combustion engine, where fuel is burned outside the engine and the energy created from that burning is what powers it. Steam engines are the best example of this. Coal is burned outside of the engine, which heats water to produce steam, which then powers the engine.

Most folks think that in the world of mechanized movement, steam-powered external combustion engines came before the internal combustion variety. The reality is that the internal combustion engine came first. (Yes, the ancient Greeks messed around with steam-powered engines, but nothing practical came from their experiments.)

In the 16th century, inventors created a form of internal combustion engine using gunpowder as the fuel to power the movement of the pistons. Actually, it wasn’t the gunpowder that moved them. The way this early internal combustion engine worked was you’d stuff a piston all the way to the top of a cylinder and then ignite gunpowder beneath the piston. A vacuum would form after the explosion and suck the piston down the cylinder. Because this engine relied on the changes in air pressure to move the piston, they called it the atmospheric engine. It wasn’t very efficient. By the 17th century, steam engines were showing a lot of promise, so the internal combustion engine was abandoned.

It wouldn’t be until 1860 that a reliable, working internal combustion engine would be invented. A Belgian fellow by the name of Jean Joseph Etienne Lenoir patented an engine that injected natural gas into a cylinder, which was subsequently ignited by a permanent flame near the cylinder. It worked similarly to the gunpowder atmospheric engine, but not too efficiently.

Building on that work, in 1864 two German engineers named Nicolaus August Otto and Eugen Langen founded a company that made engines similar to Lenoir’s model. Otto gave up managing the company and started working on an engine design that he had been toying with since 1861. His design led to what we now know as the four-stroke engine, and the basic design is still used in cars today.

I’ll show you how the four-stroke engine works here in a bit, but before I do, I thought it would be helpful to go through the various parts of an engine so you’ll have an idea of what’s doing what in the four-stroke process. There is terminology throughout these explanations that relies on other terms in the list, so don’t worry if you get confused at first. Read through the whole thing to get an overall grasp, and then read it again so you have a basic understanding of each piece as it’s being talked about.

Engine Block (Cylinder Block)

The engine block is the foundation of an engine. Most engine blocks are cast from an aluminum alloy, but iron is still used by some manufacturers. The engine block is also referred to as the cylinder block because of the big hole or tubes called cylinders that are cast into the integrated structure. The cylinder is where the engine’s pistons slide up and down. The more cylinders an engine has the more powerful it is. In addition to the cylinders, other ducts and passageways are built into the block that allow for oil and coolant to flow to different parts of the engine.

Combustion Chamber

The combustion chamber in an engine is where the magic happens. It’s where fuel, air, pressure, and electricity come together to create the small explosion that moves the car’s pistons up and down, thus creating the power to move the vehicle. The combustion chamber is made up of the cylinder, piston, and cylinder head. The cylinder acts as the wall of the combustion chamber, the top of the piston acts as the floor of the combustion chamber, and the cylinder head serves as the ceiling of the combustion chamber.

Cylinder Head

The cylinder head is a piece of metal that sits over the engine’s cylinders. There are small, rounded indentations cast into the cylinder head in order to create room at the top of the chamber for combustion. A head gasket seals the joint between the cylinder head and cylinder block. Intake and outtake valves, spark plugs, and fuel injectors (these parts are explained later) are also mounted to the cylinder head.

Piston

Pistons move up and down the cylinder. They look like upside down soup cans. When fuel ignites in the combustion chamber, the force pushes the piston downward, which in turn moves the crankshaft (see below). The piston attaches to the crankshaft via a connecting rod, aka the con rod. It connects to the connecting rod via a piston pin, and the connecting rod connects to the crankshaft via a connecting rod bearing.

On the top of the piston, you’ll find three or four grooves cast into the metal. Inside the grooves piston rings are put in. The piston rings are the part that actually touch the walls of the cylinder. They are made from iron and come in two varieties: compression rings and oil rings. The compression rings are the top rings and they press outward on the walls of the cylinder to provide a strong seal for the combustion chamber. The oil ring is the bottom ring on a piston and it prevents oil from the crankcase from seeping into the combustion chamber. It also wipes excess oil down the cylinder walls and back into the crankcase.

Crankshaft

The crankshaft is what converts the up and down motion of the pistons into a rotational motion that allows the car to move. The crankshaft typically fits lengthwise in the engine block near the bottom. It extends from one end of the engine block to the other. At the front of the end of the engine, the crankshaft connects to rubber belts which connect to the camshaft and delivers power to other parts of the car; at the back end of the engine, the camshaft connects to the drive train, which transfers power to the wheels. At each end of the crankshaft, you’ll find oil seals, or “O-rings,” which prevent oil from leaking out of the engine.

The crankshaft resides in what’s called the crankcase on an engine. The crankcase is located beneath the cylinder block. The crankcase protects the crankshaft and connecting rods from outside objects. The area at the bottom of a crankcase is called the oil pan and that’s where your engine’s oil is stored. Inside the oil pan, you’ll find an oil pump that pumps oil through a filter, and then that oil is squirted on to the crankshaft, connecting rod bearings, and cylinder walls to provide lubrication to the movement of the piston stroke. The oil eventually drips back down into the oil pan, only to begin the process again

Along the crankshaft you’ll find balancing lobes that act as counterweights to balance the crankshaft and prevent engine damage from the wobbling that occurs when the crankshaft spins.

Also along the crankshaft you’ll find the main bearings. The main bearings provide a smooth surface between the crankshaft and engine block for the crankshaft to spin.

Camshaft

The camshaft is the brain of the engine. It works in conjunction with the crankshaft via a timing belt to make sure intake and outtake valves open and close at just the right time for optimal engine performance. The camshaft uses egg-shaped lobes that extend across it to control the timing of the opening and closing of the valves.

Most camshafts extend through the top part of the engine block, directly above the crankshaft. On inline engines, a single camshaft controls both the intake and outtake valves. On V-shaped engines, two separate camshafts are used. One controls the valves on one side of the V and the other controls the valves on the opposite side. Some V-shaped engines (like the one in our illustration) will even have two camshafts per cylinder bank. One camshaft controls one side of valves, and the other camshaft controls the other side.

Timing System

As mentioned above, the camshaft and crankshaft coordinate their movement via a timing belt or chain. The timing chain holds the crankshaft and camshaft in the same relative position to each other at all times during the engine’s operation. If the camshaft and crankshaft become out of sync for whatever reason (the timing chain skips a gear cog, for example), the engine won’t work.

Valvetrain

The valvetrain is the mechanical system that’s mounted to the cylinder head that controls the operation of the valves. The valve train consists of valves, rocker arms, pushrods, and lifters.

Valves

There are two types of valves: intake valves and outtake valves. Intake valves bring a mixture of air and fuel into the combustion chamber to create the combustion to power the engine. Outtake valves let the exhaust that’s created after the combustion out of the combustion chamber.

Cars typically have one intake valve and one outtake valve per cylinder. Most high-performing cars (Jaguars, Maseratis, etc.) have four valves per cylinder (two intake, two outtake). While not considered a “high performance” brand, Honda also uses four valves per cylinder on their vehicles. There are even engines with three valves per cylinder — two inlet valves, one outtake valve. Multi-valve systems allow the car to “breathe” better, which in turn improves engine performance.

Rocker Arms

Rocker arms are little levers that touch the lobes, or cams, on the camshaft. When a lobe lifts one end of the rocker, the other end of the rocker presses down on the valve stem, opening the valve to let air in to the combustion chamber or letting exhaust out. It works sort of like a see-saw.

Pushrods/Lifters

Sometimes camshaft lobes touch the rocker arm directly (as you see with overhead camshaft engines), thus opening and closing the valve. On overhead valve engines, the camshaft lobes don’t come into direct contact with the rocker arms, so pushrods or lifters are used.

Fuel Injectors

In order to create the combustion needed to move the pistons, we need fuel in the cylinders. Before the 1980s, cars used carburetors to supply fuel to the combustion chamber. Today, all cars use one of three fuel injection systems: direct fuel injection, ported fuel injection, or throttle body fuel injection.

With direct fuel injection, each cylinder gets its own injector, which sprays fuel directly into the combustion chamber at just the right time to combust.

With ported fuel injection, instead of spraying the fuel directly into the cylinder, it sprays into the intake manifold just outside the valve. When the valve opens, air and fuel enter the combustion chamber.

Throttle body fuel injection systems sort of work how carburetors did, but without the carburetor. Instead of each cylinder getting its own fuel injector, there’s only one fuel injector that goes to a throttle body. The fuel mixes with air in the throttle body and then is dispersed to the cylinders via the intake valves.

Sparkplug

Above each cylinder is a sparkplug. When it sparks, it ignites the compressed fuel and air, causing the mini-explosion that pushes the piston down.

So now that we know all the basic parts of the engine, let’s take a look at the movement that actually makes our car move: the four-stroke cycle.

The above illustration shows the four-stroke cycle in a single cylinder. This is going on in the other cylinders as well. Repeat this cycle a thousand times in a minute, and you get a car that moves.

Well, there you go. The basics of how a car engine works. Go take a look under your car’s hood today and see if you can point out the parts that we discussed. If you’d like some more info on how a car works, check out the book How Cars Work. It has helped me out a lot in my research. The author does a great job breaking things down into language that even the total beginner can understand.

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