Figure 5 - MTU: Sequential Turbocharging System turbocharger gas inlet valves is readily accomplished with microprocessor control, and is probably compatible with the control systems now entering the market.

Ceramic turbochargers began moving into automobile engines in 1987. A Japanese company reportedly is making more than 5,000 ceramic rotors a month which are going into limited edition automobiles. While this is a remarkable achievement it does not yet necessarily mean that the ceramic turbocharger can be economically made as aerodynamically efficient as a metal turbine. Coefficient of expansion considerations suggest wide clearances unless a ceramic housing is used in which case a tighter clearance is possible. The sensitivity of the ceramic rotor to particulate impact degradation suggests a particulate trap be used to capture particles over 100 microns (0.004") in diameter. Ceramic fiber or whisker reinforced ceramics should improve the strength and toughness of ceramic rotors. Lighter weight ceramic turbines and compressors should allow more flexibility in turbocharger shaft bearing selection. Ceramic turbochargers for heavy duty diesel applications will have to provide an advantage in improved performance or lower cost with comparable performance. The glamour associated with advanced technology will make a stronger input in the automotive market than in commercial trucking. Having said that, rapid progress in ceramic technology could well make ceramic turbochargers viable candidates for improved diesel performance.


Probably the most challenging near term problem confronting the diesel engine community is compliance with EPA emissions regulations. The EPA regulations for NO and particulates are shown in Table 1 fSr heavy duty truck engines along with typical levels for current production engines.

Compliance with the emissions regulations by the engine manufacturers must take into account the variance 1n production engines, a deterioration factor and must allow a design margin.

Table 1

Implementation Particulates N0V


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