The crankcase is made of high mechanical strength cast iron.The crankshaft is supported by five main bearings.The cylinders are formed directly on the crankcase and are divided into three size categories plus one oversize.Special channels in the crankcase walls carry coolant and lubrication fluid.Compared with the naturally aspirated version, the new cylinder block/crankcase for the TJet differs through the more efficient internal circulation of the coolant and through the height which has been increased by 0.8 mm
LOWER CRANKCASE
The lower crankcase is made from die-cast aluminium alloy with cast iron main bearing caps.The machining of the supports and main bearing caps is carried out together with the crankcase.The matching with the upper crankcase is achieved by means of bolts and locating dowels which guarantee the precision of the fitting.There is a bead of sealant between the two crankcases to prevent oil leaks.The upper and lower crankcases are illustrated in the diagram below.
The functions of the lower crankcase are:- it constitutes the load carrying structure with the upper crankcase;- it supports the crankshaft loads and reactions;- it allows the return of the engine and turbocharger lubrication oil to the sump;- it supports the engine oil sump;- it supports the intermediate shaft bearing support.
