Tradition obliges
In 1972, the automobile plant in Ingolstadt, with the launch of the Audi 80, which, thanks to its light design and compact dimensions, comfort and spaciousness of the interior and trunk, as well as modern engines and exemplary running gear, set the high standard for a middle-class car. The Audi A4, which continues the tradition of the Audi 80, entered the market in November 1994. In its next model, Audi deliberately abandoned large external dimensions. Nevertheless, thanks to the skillful use of space, the increase in track and wheelbase, it was possible to significantly improve the ratio of the internal length of the body to the base for those sitting in the cabin.
Engines
In addition to the two new 1.8-litre five-valve engines, the Audi A4 features a redesigned 1.6-litre four-cylinder, two-valve engine with a newly designed cross-flow cylinder head for the A4. In addition, two engines already known from the Audi 80 are also used: a V6 with a displacement of 2.6 liters and 2.8 liters. Each one is:
- four-cylinder engine with a displacement of 1.6 liters with a power of 74 kW
- four-cylinder five-valve engine with a displacement of 1.8 liters with a power of 92 kW
- four-cylinder five-valve engine with a displacement of 1.8 liters and a turbocharged power of 110 kW
- V6 with a displacement of 2.6 liters and a power of 110 kW
- V6 with a displacement of 2.8 liters and a power of 128 kW
With such a gradation, it is of interest to be able to choose between two power plants of the same power, because as a four-cylinder engine with a displacement of 1.8 liters. With. turbocharged, and V6 with a displacement of 2.8 liters have the same power of 110 kW. With the same power, there are differences in concept performance: depending on what the buyer prioritizes in an engine, a choice can be made between increased efficiency or greater comfort and smoothness.
Five-valve engine technology
New head on old block: The 1.6l engine for use in the Audi A4 has a new cross-flow cylinder head.
Five-valve engine technology, turbocharging and an aftercooler at 110 kW make the 1.8-litre engine a marvel of driving and traction culture.
The five-valve engine has two overhead camshafts, one of which drives three intake valves while the other opens both exhaust valves.
Engine power, along with various parameters such as displacement and speed, depends to a large extent on how quickly gas exchange can take place. The more fresh gas in the same unit of time can enter the combustion chamber, the more intense the power output. Most Audi engines have a long stroke, which means the piston stroke is larger than the bore. Long-stroke engines allow for short designs, they are lighter than short-stroke engines, they are smooth in operation, especially at idle, and are distinguished primarily by the fact that they already reach maximum torque at low speeds.
The filling of the combustion chamber depends primarily on the opening and closing of valves and flow sections in the valves and channels of the cylinder head.
Three intake and two exhaust valves, i.e. five in total for each cylinder, provide maximum flow area. It follows from the area of \u200b\u200bthe valve disc and the magnitude of its opening stroke. Compared to common multi-valve concepts, five-valve technology in long-stroke engines offers the greatest possible advantages in terms of cylinder filling rate.
At the same time, the technology of the five-valve engine allows for a combustion chamber design with a centrally located spark plug, and as a result, a short ignition spark path is possible to ensure fast, efficient combustion of the working mixture. This also reduces the risk of detonation, and high compression makes it possible to use the fuel intensively. The combustion of the working mixture in a five-valve engine is carried out «softer», than in two- and four-valve engines. Since, due to the larger cross-section of the valves, the forces that actuate them are much weaker, in general, pleasant acoustics are created during the operation of a five-valve engine.
The five valves are actuated by two camshafts directly via hydraulic poppet lifters. As has long been customary in Audi, the valve clearance is not adjustable.
The intake camshaft serves three valves on each cylinder, the exhaust camshaft two. Both camshafts are connected by a chain, the drive from the crankshaft is provided by a toothed belt.
Engine tuning philosophy
The high traffic density on our streets requires a different engine concept from that which existed back in the 80s: it is not the amount of maximum power that is in demand, but the balance of fuel consumption, the range of power offered, the nature of the exhaust gases and noise. The engine design selected by Audi with powerful torque in the lower speed range allows driving at low revs and thus a noticeable reduction in fuel consumption.
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