In part two, Tigercat tells us what we need to know about the management of turbochargers.
The May 1 issue of Logging-on brought the first part of Tigercat’s valuable information on turbochargers. In this issue, we continue examining important management information to ensure maximum service from your turbochargers.
The oil must be warmed before working the machine and the turbo must be allowed to cool before shutdown. Proper lubrication is essential to cool the turbo. Turning off the engine right after working the machine hard means the lubricating oil flow by the pump will be turned off while the turbo is still spinning at high rpms for several minutes. With no oil, there is no way to quickly remove the heat. This can cause premature wear to the shaft, bearings and seals and shorten the life of the turbo. The same can happen by not allowing enough time for the oil to warm on startup. Cold oil moves more slowly, delivering inadequate lubrication to the bearing.
The tolerances within the rotating parts of the turbo are very small and rely on good quality oil to keep all parts moving flawlessly. Replace the oil at the recommended service intervals or even sooner if there is a risk of contamination. Dirty engine oil can quickly reduce overall life as it permanently scores the bearings and shaft. These imperfections in the surface of the material then leave room for further contaminants to settle and accelerate wear on the parts. A rough surface also restricts oil flow and its ability to remove the heat.
During the combustion process of the engine, there are combustion vapours (blow-by gas) that escape past the piston rings into the engine crankcase and mix with the oil vapours. To prevent over-pressuring the sump, these vapours are filtered from the oil and returned to the turbo inlet pipe, while returning the condensed oil to the sump. On Tigercat FPT 6.7 and 4.5 litre engines, the CCV upper case filter is located directly above the engine flywheel housing and is specifically designed to match the engine. For this reason, only Tigercat branded filters should be used. CCV filters have a specific oil separation media to control the blow-by gasses and have been designed and manufactured specifically for the application with proprietary materials to work in unison with the rest of the system.
Seeing some oil at the turbo is normal – the combustion vapours directed to the intake can be mixed with some residual oil that is usually burned during engine combustion. Some of this oil can settle in the pipe just before the turbo inlet and as such, it is normal to see oil in small quantities. What is important to remember is to replace the CCV filter at the recommended service interval. This often neglected filter plays a very important role. Incorrectly servicing this component can result in filter saturation and allow oil to build up at the turbo compressor inlet and outlet. This reduces engine performance and turbo boost pressure due to the restriction on the compressor wheel caused by coking and can negatively affect components downstream of the turbo exhaust. Left too long, this can lead to turbo failure or even engine failure.
Keeping an eye on the machine’s boost pressure can help catch any concern in the early stages. Should the boost pressure appear to be low or drop suddenly, the operator should be proactive and adjust/ investigate accordingly. Since it is easily accessible and fastened with only four bolts, the turbo is often replaced prematurely in a low boost pressure event. Some factors to review and consider beforehand are loose or worn charge air connections, restricted air filters, blocked precleaners, saturated CCV filters and worn gaskets between the turbo and intake/exhaust manifold.
In an event where the shaft or compressor wheel breaks, the turbo boost pressure will decrease significantly. At this time, stopping the engine immediately is crucial as continuous operation can allow a large amount of oil to reach the engine intake and enter the cylinder chambers. The significant amount of power generated from the oil mixing with the fuel and the air during the combustion process can cause severe damage and has the potential to bend the connecting rods resulting in an engine replacement. The oil can also contaminate exhaust catalysts, resulting in extensive repairs.
The information was compiled by Jean-Marc Labelle, Tigercat’s service engineer. Source