What are 3 types of motor controllers

Overview of all automotive technology topics
and the gasoline engine

Here technical basics are explained in a way that is understandable for the layperson!



We deliberately refrained from detailed explanations of complex relationships.

On this page is:


Overview of all car technology, scooter topics



Engines explained clearly


Motor comparison, functions, cooling system, motor control and much more


The different ignition systems




The electronic engine control


The basics of electrics are clearly explained


Car electrics, charging system, efficiency levels, electrical consumers



The air conditioning, function, components



Technology for scooters, motorcycles and mopeds






Useful smartphone accessories and well-tested apps for drivers







The gasoline engine

The history:

Nikolaus August Otto experimented around 1860 - like many others during this period - with internal combustion engines.
His brilliant idea was to compress the air in the combustion chamber before ignition. It is said that he himself was very shocked by the enormous combustion, as its construction had almost blown apart during the first attempts due to the enormous force. In practice, he introduced the compression cycle. This increased the efficiency of the work done enormously.

In 1876 Otto applied for a patent for his further developed combustion engine.

Even after almost 140 years, with numerous inventions and technical advances, almost all engines in our vehicles still work, based on Otto's invention.

The four-stroke petrol engine:

First of all, I would like to clear up the mess of 4 stroke and 4 cylinders once and for all! In a 4-stroke gasoline engine, a cylinder requires 4 strokes for a complete work cycle. 4 cylinders simply means the NUMBER of cylinders in which the work cycle is carried out. So 4 cylinders only says HOW MANY pistons are there, i.e. the power is quadrupled, but that says nothing about the way it works!
There are also 4 cylinder 2 stroke engines!

For a complete working cycle (4 cycles) of a cylinder, the crankshaft needs 2 revolutions, so the piston makes 4 strokes.

1st cycle, intake cycle
The inlet valve is open and the piston sucks the fuel-air mixture into the cylinder as it descends.

2nd stroke, compression stroke
Both valves are closed and the piston compresses the fuel-air mixture as it goes up.

3rd cycle, work cycle
Both valves are closed, the fuel-air mixture is ignited by means of a spark plug, and the combustion gases that suddenly develop push the piston downwards. This is the only cycle in which power is generated.

4th stroke, exhaust stroke
The exhaust valve opens and the piston pushes the burned gases out as it goes up.

Then it starts again with measure 1!

OT and UT

Technically correct is "going downhill"
the path of the piston from the highest point that the piston in the cylinder can reach (top dead center = TDC, reversal point)
after the lowest point that the piston in the cylinder can reach (bottom dead center = BDC, reversal point)
"Going up" is analogous to this, the path of the piston from BDC to TDC.

For the sake of better understanding, I have omitted these terms.


The mechanical motor control:

The inlet and outlet valves must be opened and closed for gas exchange. The camshaft is responsible for this.
The force developed by the engine on the crankshaft must drive the camshaft so that 1 work cycle (4 cycles) can be implemented. The crankshaft rotates 2X and the camshaft 1X. This can be done in different ways:

  • Spur gears: The power is transmitted from the crankshaft to the camshaft by means of gears.
  • Control chain: The transmission is realized with a chain (similar to a bicycle chain).
  • Toothed belt: The same with a belt (similar to a V-belt) but with teeth.
  • Vertical shaft: A bevel gear drive that is practically no longer of any importance in normal vehicle construction.
Most of the time, these gear ratios are also used to drive distributors or injection pumps.

A detailed article about the timing belt - material, structure and advantages - can be found on the timing belt repair instructions page.


The valve clearance

Everyone is talking about valve clearance and hardly anyone knows what it is actually used for.


In principle a simple thing:
All metals expand when they get warm. So the cylinder head and the tappets, pushrods, and all parts that belong to the valve train also expand when the engine is warming up. Since the cylinder head and valve train are usually of different "lengths" and different metals are used, and since you want to make sure that the valve always closes correctly, even when it is worn, you need some play.

Whereas in the past you had to adjust the play with the feeler gauge, now maintenance-free hydraulic valve lifters are used.

Instructions for adjusting the valve clearance

Any questions on these topics? Ask your questions in our auto forum.

Help others with your knowledge and experience or simply exchange ideas with other car friends.