Turbos – A guide
To begin – what is a turbo?
A turbo is known as a turbocharger and is a turbine forced and driven device which boosts the internal engine combustion power output and efficiency, through forcing extra air into a combustion chamber. It relies on the compressor to proportionately force extra air and fuel, rather than atmospheric pressure into the combustion chamber. A turbo aims at improving engine efficiency through boosting the density of intake gas and facilitating more power per engine cycle.
Different types of turbos
Single turbochargers offer limitless variability, differing compressor wheel size and a turbine which leads to totally different torque characteristics. Large single turbos offer high and top-end power, while smaller single turbos offer low-end but better grunt because they spool faster. Other single turbo types include the journal bearing and ball bearing single turbos. Ball bearings feature less compressor friction and spin on the turbine; hence, being faster to spool.
Turbos for boats
Marine turbochargers are usually exposed to harsh environments with salt etc. almost all marine turbochargers that we renovate ourselves come with our stainless steel sleeve. The sleeve prevents the turbine housing from rusting up which is otherwise very common on marine turbochargers and significantly extends the life of the turbon. Do not forget to check the oil pipes so that they are not overcooked, as well as that the air filter is replaced or cleaned. Engine oil and oil filters should always be changed during turbo change.
Twin-turbo means adding an extra turbocharger to the engine; such as in V6 or V8 engines. This is achieved by assigning a single turbo to operate with each bank cylinder. Note that, a small turbo can be used with a larger turbo at low RPM and higher RPM respectively. This paves the way for a wider RPM operation range, better torque and more power at high RPMs.
Twin-scroll turbochargers use a divided-inlet housing turbine and manifold exhaust to pair the right engine cylinders independently per scroll. They deliver exhaust gas energy efficiently to the turbo for purer and denser air provision in the cylinder. Once more energy is directed to the exhaust turbine, it provides more power.
Variable Geometry Turbo
Variable geometry is considered an exceptional form of turbocharging. This is because VGTs production is limited due to its exotic material requirements and costs. The area to radius ration is altered by the internal vanes to match the RPM. For low RPM, low area to radius ratio is required to boost the velocity of the exhaust gas and spool up the turbocharger quickly.
Variable Twin-Scroll Turbo
The variable twin-scroll turbo combines the benefits of a twin-scroll and variable geometry turbo, using a valve to redirect exhaust airflow to a single scroll, or changing the amount opened by the valve to allow the spilling of exhaust gases in both scrolls.
Electric turbos eliminate turbo lag and lower engine speeds for normal turbos, in cases where conventional turbos do not perform efficiently.