Modern diesel engines require compressed air to operate most efficiently. This compressed air is created by the use of a turbocharger. Turbochargers have been utilized in many applications because of their reliability, efficiency and ease of use. By design, a turbocharger or “turbo” uses the air flowing out of the exhaust to rotate a turbine wheel. That turbine wheel is attached to a compressor wheel via a shaft. The compressor wheel pressurizes the air and thus increases the density of the intake charge. This increase in pressure forces more oxygen rich air into the cylinder and provides the engine the ability to burn more fuel as the engine RPM increases. As the engine RPM increases, so does the RPM of the turbo. In fact, turbos used on dodge diesel trucks can have an RPM of up to 125,000! This design is different from that of a “supercharger” which is mechanically driven from the engine, often from a belt that is connected to the vehicles crankshaft. This process is often referred to as “forced induction.”
The increase in pressure created by the turbo is called “Boost.” As the engine idles, an insignificant increase in pressure is created. When the RPM of the engine increases, so does the exhaust pressure going through the turbine side turbo. When this happens, the turbine wheel spins enough to allow the compressor wheel to generate boost.
Another variable that significantly impacts the performance of a turbocharger is the size of the exhaust housing. Boyle’s law in physics states that at a given temperature, volume and pressure are inversely proportional. This basically means that at a constant temperature, the pressure of a volume of gas increases as the space decreases. It also means that as the space increases, the pressure decreases. The important thing to note here is that as the size of the turbine housing (or exhaust housing) increases, the relative speed and pressure of the exhaust coming out of the engine also decreases. Lower exhaust pressures rotate or “spool” the turbo slower than higher exhaust pressures. So, with a larger exhaust housing, one could expect to see a slower spool up. This slower spool up is often referred to as “turbo lag” or “hesitation.” One could also describe the lag as “turbo response time.” Knowing this, it may seem like the best choice would be a small turbine housing. The smaller the turbine housing is, the quicker the turbo will spool, however, as the turbo builds boost, the exhaust gas temperature or “EGT” for short, will become too hot often risking damaging the engine and other vital components. On the other hand, if the exhaust housing is too large, the engine may not be able to spool the turbo, given the lower pressures of a large housing, and therefore an insignificant quantity of boost will be made.
The team of experts at Source Automotive have years of experience building and testing various turbo combinations on Dodge Diesel Trucks. This experience comes from first hand knowledge. We daily drive these trucks. We tow on a regular basis with these trucks. We drag race these trucks testing various combinations of single turbos, dual, triple & even quad charger set ups, utilizing the Cummins engine. Due to the overwhelming quantity of variables and the complexity of choosing the correct turbo, let the experts at Source Automotive help you choose a turbo(s) that is carefully selected to your needs and desires. Choosing a turbo does not have to be a costly mistake that turns your truck into a “laggy pig.” Let Source Automotive help you pick what is best for your unique application.