 Hey everyone, Emmy here again and welcome to another episode of Cobb U. Now we've made a lot of progress in this series so for those of you who aren't caught up, I highly recommend going back and starting with episode one. For those of you that are caught up, let's keep going. In the previous episode we discussed the components that make up the fueling system and its basic functions. Now we've come to the process that happens once you get that proper air fuel mixture, the combustion cycle. Today's video will be going over a basic overview of what happens during the four stroke combustion cycle, as well as going over the major internal components of the engine that make it all possible. So with that being said, sit back, crack open a cold beverage of choice and let's get to it. For the sake of today's demonstration, we'll be using a graphic animation of a generic inline four cylinder engine. Let's start with the engine block. It provides us with the foundation that all of our other components will be built upon. Next we have the rotating assembly, which is comprised of a crankshaft, connecting rods, and pistons. The movement of these parts is what provides us with the power to drive whatever our motor is attached to. After that comes our cylinder head, which is comprised of not only the head casting itself, but also includes our valves, valve springs, lifters, as well as camshafts. The cylinder head will also house our spark plugs and in the case of direct injected cars, our fuel injectors too. Unless, but certainly not least, a timing belt or chain connects our crankshaft and camshafts together so that they'll work in harmony. Now that our engine, which at this point can be referred to as a long block, is assembled, we can go over each one of the strokes of the combustion cycle so that we can get a better understanding of how we make power. Now keep in mind that we're using a simplified model because camshaft design can change the timing of valve events in relation to the combustion cycle. The first of the four strokes is the intake stroke. As the piston begins traveling to the bottom of the cylinder, the intake valves open. Cylinder volume increases as the piston goes down, creating a vacuum which higher pressure air in the manifold moves to fill. This pressure differential is what brings the air fuel mixture into the cylinder. Remember, air will always flow from higher pressure to lower pressure areas. As the intake stroke comes to an end, the intake valves start to shut. Up next is the compression stroke. Here the piston travels up, compressing what we have in the cylinder. On a port injected car that would be our complete air fuel mixture. This is where the differences of direct injection come into play. With our direct injector in the cylinder, we're able to have more control over when fuel is delivered. On a DI engine, air flows from the manifold into the cylinder without fuel on the intake stroke. Fuel is injected independently, usually starting on the intake stroke, but sometimes starting even later during the compression stroke. The injector delivers a precise amount of fuel at the exact moment it's needed to maximize efficiency and minimize waste. Just before the piston reaches the top, the air fuel mixture is ignited by the spark plug. The combustion process is sometimes referred to as a tiny explosion, but in reality it's a controlled burn. The heat of combustion and expansion of gases creates pressure which applies downward force on the piston during the third stroke, the combustion stroke. The rotating assembly comprised of the piston, rod and crankshaft moves as a unit. The motion starts with cylinder pressure pushing the piston downward, the piston moves the rod, the rod in turn moves the crank, spinning the whole rotating assembly and driving the transmission. And finally we have our exhaust stroke. As the piston reaches the bottom of the cylinder at the end of the combustion stroke, our exhaust valves begin to open, releasing pressure. The upward movement of the piston pushes out most of the remaining exhaust left in the cylinder and the exhaust valves close. After the cycle is complete it just repeats and repeats and repeats until you either shut your car off or something happens that keeps it from repeating. But let's hope that doesn't happen. Lastly when doing this type of part install you will generally use these kinds of tools. Every freaking tool in your garage and more. No kidding aside you're gonna need a lot of tools to do this and every setup is different so if I were to list them all off I'd be here all day. And now it's time for the pro tip of the day. Today we're going to be talking spark plugs, more specifically heat ranges. You might have had someone tell you that as you start modifying your car you're going to want to run a set of spark plugs that are one step colder or something to that effect. As you make more power everything gets hotter. This includes our spark plug to the point where the tip gets red hot. Now if it gets too hot it can prematurely light off your air fuel mixture during the compression stroke. This is called pre-ignition because combustion happens before the plug sparks which can be harmful to your motor. A colder plug removes heat from the combustion process and maintains cooler spark plug temperatures making pre-ignition less likely to occur. Now a colder plug isn't always what you need. A colder plug is less ideal when you're not driving aggressively or not making much more than stock power levels. It also won't generate as much heat when you're trying to cold start your engine so in very cold climates a very cold plug may be a concern. A colder plug can also make the combustion process less efficient during normal driving. There are various heat ranges of spark plugs and usually going one step colder than stock isn't going to cause any issues. However going two or more steps colder than stock is generally reserved for race only vehicles. So while upgrading your plugs isn't usually necessary for mild modifications it's generally a good rule of thumb to upgrade one step colder spark plugs when increasing power 50 to 100 horsepower or more over stock. That's going to do it for this episode. In our next video we're going to finish our journey through the engine with the exhaust system. Thanks for joining us. Be sure to subscribe to our YouTube channel so you can check out future episodes. I'm Emmy your host for CobbU. Remember check out Cobbtuning.com for all your parts and tuning needs. Do you like the storage solutions featured in our studio? Then visit sonictoolsusa.com to get more detailed product information.