| Variable Turbine Geometry The broad engine-speed range of a passenger-car engine makes regulation of the turbocharger necessary in order for almost constant boost pressure to be available across the widest engine-speed range possible. The variable turbine geometry continually adjusts the output of the turbines so that the entire exhaust gas energy can be used to regulate boost pressure. Adjustable vanes guarantee this across a wide control range while at the same time maintaining a high level of efficiency. If the gas pressure is reduced at a low engine speed, the control function adjusts the vanes so that the cross-section is reduced and gas pressure accelerated and thus increased. If the exhaust gas pressure is increased at a higher engine speed, the control function increases the cross-section of the supply line by adjusting the vanes. Turbochargers with variable turbine geometry are particularly efficient at partial load and turbo lag is eliminated. They increase engine power, improve its response significantly and can also have a beneficial effect on its emissions.
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