|Driven by either the crankshaft or the exhaust-gas flow|
The charging can be done either by the exhaust-gas flow (turbo-charger), a mechanical connection to the crankshaft (compressor and G-charger spiral-type), or the direct contact of the fresh gases and is controlled
through a mechanical connection, (the Comprex-charger). The high temperatures during compression make an (air-to-air-) or a coolant-to-air heat exchanger between the compressor and the engine-air-collection pipe absolutely necessary for the efficiency.
|Charging is mostly more reasonable that an increase in capacity.|
Fundamentally, through charging, more air and thus more oxygen is pumped into the cylinder instead of being sucked in, this improves the quality of the fuel-air filling. Both the performance and the torque are
increased, also in the important lower RPM range without raising the cubic capacity. In addition, the fuel consumption and the emission are reduced. This however, mostly only in comparison with normally aspired
engines producing the same performance but having a greater cubic capacity. Indeed, the values climb a little, when compared with engines having the same capacity. There are however, exceptions, if e.g., in the
Diesel engine, the increased performance through charging is not used, it will, e.g., simply allow more air to flow through the engine, which improves the quality of the exhaust-gas emission.
|(Partial) avoidance of the charger-drive performance loss.|
Basically, charging always means, first of all, a somewhat higher performance loss. The turbo-charger also doesn't get it's energy free of charge, because the back-pressure in the exhaust system increases. Indeed,
more performance is certainly drawn off in the case of the compressor. If these losses are properly applied in the engine management, they can however, even be turned into a performance gain, e.g., through the very
late closing of the intake-valve the geometric compression can be clearly reduced and compensated for by the charging. In the meantime, there is, for this reason, a special, adjustable exhaust-valve timing. Through
the rapidly reduced charging pressure, this can, under certain operating conditions, lower the performance loss caused by unnecessarily high compression. The important thing is, that through this regulation, the
adaption of the compression to the petrol engine knocking-limit, is possible.
|Unfavourable turbo-lag decreases slowly.|
Should one wish to draw off only a little performance for the charging, one would more than likely choose the turbo-charging. Very fast adjustment speeds, e.g., in VTG-chargers and small components, reduce the essential disadvantage of delayed response (turbo-lag). The more suitable candidate for charging,
still seems to be the Diesel engine because no obstacles disturb the free-flow of air to the combustion chambers. One gathers the impression that the compressor appears to assert itself as far as petrol engines are
concerned. Indeed, also in this case, there are already vehicles with VTG-chargers. Smaller cars with a
particularly low fuel consumption will still, for production-cost reasons, be fitted with normally aspired engines.
|Charging and the iron-clad laws of motor vehicle technology.|
The charger is looked at by some automobile-technology experts, as being a second engine. An interesting theory, particularly as Ferrari apparently, even had one with fuel-injection in the compressor. Then e.g., the
turbo-charger would become a genuine gas-turbine, which would share the work with the pistons. Oh yes, the subject of charging does indeed mix up the doctrines of motor-technology. One of these doctrines is, that
cubic capacity (or the lack thereof) cannot be compensated for by anything else. Also the current compression limits of between 9 : 1 and 12,5 : 1 for petrol engines, are no longer valid, because of course, depending
on the operating conditions, one can drive with a staggered charging pressure. Apart from the geometric-, there is also the dynamic compression. And if you consider, that thoroughbred racing engines (e.g., from
BMW) which have a particularly short lifespan, are said to have had charging pressures of up to 5 bar ... 02/14