Top dead center and bottom dead center: definition and operation
In mechanics, the neutral point corresponds to the position of the piston reciprocating in its cylinder. There are two blind spots: top dead center, or TDC, and bottom dead center, or PMB. At top dead center, the piston is higher in its stroke, while it is at the very bottom of the cylinder at bottom dead center. This corresponds to different combustion cycles.
🚗 What is top dead center?
The operation of an internal combustion engine, like that of a car, is based on pistons... Each of these pistons slide on cylinder and is used to compress fuel and gas to create an explosion, the energy of which drives the engine.
Modern cars are equipped with a 4-stroke engine that operates in four different cycles:
- Theinput air / gasoline mixtures;
- La (strength) this mixture by lifting the piston;
- Theexplosion when the piston is in the highest position;
- Theexhaust when the piston rises.
To create these four phases, the pistons work with other parts, including crankshaft who teaches them, but also valves which are the parts that block the entrance to the cylinders. THE 'camshaft allows these valves to be opened and closed, allowing inlet in the first phase and exhaust in the fourth phase.
We are talking about alternative piston when the piston slides in the cylinder like a pump, as in internal combustion engines. However, in the case of a reciprocating piston engine, there are two points that are called the neutral point: top dead center on one side, bottom dead center on the other.
These dead spots have nothing to do with the transmission. It just so happens that the term "neutral" was taken by analogy to refer to neutral position: therefore, this position is used to refer to this position of the gear lever, but this expression is also used in finance.
Your vehicle's top dead center, often referred to as TDC, is when the piston is at the highest point of its stroke in the cylinder. Therefore, this is also the moment when the volume of the combustion chamber is at its lowest and the compression is at its highest, just before the combustion of the air-fuel mixture.
You should know that the sensor called PMH sensor, is responsible for detecting when the piston is at top dead center in your vehicle. He uses teeth flywheel... Then the TDC sensor transmits this information to the engine control unitwhich uses it to optimize fuel injection and achieve combustion that keeps your engine running.
🔍 What is bottom dead center?
Le top dead center (TDC) refers to the moment when the piston of the internal combustion engine is in the highest position in the cylinder when the compression is at its maximum. And vice versa, point Mort Bas (PMB) corresponds to the moment when the piston is in the lowest position of its stroke.
At this time, the volume of the combustion chamber is greatest: this is the end of the intake, which is to suck in air and fuel, a mixture of which will cause an explosion and combustion of the engine. Compression is naturally minimal as it is about creating a mixture, not compressing it so that it explodes.
📍 How to find top dead center?
Top dead center indicates the highest position of the piston in its cylinder. But it also has another usefulness: knowing the position of the top dead center allows detain her distribution, which is necessary for certain mechanical interventions in the engine.
Your car usually has landmarks for this setting, but sometimes you need to find the top dead center to mark it yourself. In this case, manually start the engine a few turns. You must determine the position that the piston is at the top of the cylinder just before it starts to descend: this is top dead center.
Now you know what the terms top dead center (TDC) and bottom dead center (PMB) stand for. As you already understood, these are the most extreme positions of the piston in its cylinder. You should also be aware that never two pistons will be in the same phase during combustion.
