The problem of matching turbochargers to a given diesel engine may best be considered as a mutual development program requiring the efforts of both the engine manufacturer and the turbocharger manufacturer. From given engine data and expected engine performance levels, the turbocharger manufacturer can select a turbocharger approximately suited for the particular problem.
The allowable ratio of naturally aspirated to turbocharged power is dependent on several factors some of which are mechanical limitations of the engine, allowable peak firing pressures and type of combustion chamber. Often times this determination must be based on experimental engine running which includes variation of valve and injection timing as well as changes of injector pumps and nozzles.
From the original problem statement a reasonable selection of turbine nozzle area may be made and for test purposes nozzles of various sizes close to the calculated size may be supplied for exact engine matching on the test stand.
Some factors affecting selection of the turbocharger are first, the usage to which the engine will be put; second, the ambient temperatures and pressures to which the engine will be exposed during operation and; third, the type of control system which will be used for both engine and turbocharger.
Generally speaking, it will be noted that both intercooling and pressure ratio controls impose additional range requirements on the turbocharger compressor.
Although the factors affecting turbocharger selection may sometimes be complex, if we are at least aware of the complexities we can give them reasonable consideration.