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The essential crankshaft dimensions were defined using bearing load and hydrodynamic lubrication gap calculations in conjunction with FEM. In this way the diameter and width of the main and connecting rod bearings were defined according to operational demands and the crankshaft webs also determined for greater stiffness of the journal connection. The counterweights were optimised for the rev range and load spectrum. A vibration damper could therefore be omitted.
On the drive-side a light steel-flywheel transmits torque to the clutch. An incremental toothed gear integrated in the clutch supplies the impulse for the Bosch Motronik rotational speed signal. Another incremental toothed gear in front of the camshaft gear drive is a redundancy in the rotational speed recognition. The obliquely divided steel connecting rod is manufactured from H profile like the R10 and was optimised with regard to stiffness and minimum weight by FEM calculation.
The R15 TDI used steel H-beam rods by Pankl and steel pistons with specially developed combustion bowls
connect the bearing blocks with one another, making a very stiff unit when assembled together with the upper crankcase. This means the engine and chassis have almost equal stiffness. ‘The engine’s installation height in the Dallara-built,
The exits from the titanium exhaust system on the R15 were in an unconventional location – on the rear deck ahead of the rear wing. The car’s complex aero package means that the area around the exhausts and turbochargers is incredibly tight. ‘Getting the exhausts and the filters into such a tight area was not easy because they run very hot, around 900degC,’ reveals Baretzky. ‘If you look at the road car, it’s a similar idea. You always have to have the particulate filter very close to the engine to use the maximum heat to get it operating as soon as possible. It also helps keep the engine compact.’
STEEL PISTONS One of the big steps forward in the new engine was the use of steel pistons, developed with technical partner Mahle. On the V12, aluminium pistons with fibre-reinforced bowl lips were used, but these saw reduced
its steel piston can equal
or even fall below the weight of its aluminium version
Picture 11: R15 TDI connecting rod and piston
The Mahle steel piston has a combustion bowl developed specifically for this use. The high thermal loads made using two piston spray nozzles necessary. One spray nozzle is for the piston base the other for to supply the cooling channel.
cooling purposes corresponding oil grooves with cut-off control valves are integrated in the block. The integral cast water channels with a junction to the heat exchanger have only the connection to the water coolers in closed circuits. ‘The crankcase below the main bearing centreline – the so-called bed plate – is
4.3 Piston
manufactured using an identical process to the one used for the R10 V12. It’s a complex, heavy duty, cast component and, due to directional solidification, the precision casting has equally high strength (Rm 35Mpa) and ductility, with a minimum wall thickness less than 2mm. ‘The side-mounted dry sump scavenge port and ribbings
steel flywheel transmits torque to the clutch, while an incremental toothed gear integrated in the clutch supplies the impulse for the Bosch Motronic rotational speed signal.’
Audi-designed chassis was influenced significantly by the stroke. Although the stroke was increased by nine per cent, the distance between the crankshaft centreline and the bed plate was actually reduced by four per cent, resulting in a lower installation height and a correspondingly low c of g.
‘On the drive side, a light
service life and an increase in the probability of failure. So, in cooperation with Mahle, heat- treated steel pistons were tested in the V12 and found to offer both high temperature resistance and good machining properties, leading to the V10 being designed exclusively for such pistons. The higher temperature resistance of the steel means the pistons can be shorter than the aluminium versions, resulting in a lower cylinder block height and a resultant decrease in installation space. Owing to the greater transferable force in the
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The piston is manufactured from heat-treatable steel. This material combines the properties of high temperature resistance and good machining properties. In addition to
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