TECHNOLOGY - ENGINES
Comparison: restrictor, boost pressure Year
- 10 - Restrictor size Change
2006- 2008
2 x 39.9mm
The 90 degree cylinder bank angle was retained, since it represented the best compromise regarding torsional stiffness, overall height and centre of gravity position for this car. The resulting uneven angular ignition spacing for a crankshaft with continuous, single axis crank pins has no influence in the race car
Manifold pressure
2940mbar 2009 2 x 37.9 2010 2 x 37.5mm -9.8% -11.7% 5.5-litre V12 V10
The engine’s installation height is influenced significantly by the stroke. Although the stroke was increased by 9%, the distance between the crankshaft centre-line and the base plate was reduced to by 4%. As a result the Audi engine has an extremely low installation height and a correspondingly low centre of gravity. The experience gathered in racing diesel-engine development is also reflected in this.
2750mbar -6.5% 2590 mbar
Every peripheral component was optimised with regard to modular design and quick exchange.
4.1 Engine block and bed plate
5500 12
The cylinder block (closed deck) is manufactured from an aluminium alloy casting using the low-pressure sand casting method. The cylinders are Nikasil® coated.
Evaluation of V10TDI and V12TDI concepts Base V12 TDI = 100% Length Width Height Weight
V10 TDI 5.5-litre
-13% 4% 4%
-12%
For piston cooling purposes corresponding oil grooves with cut-off control valves are integrated in the block. The integral cast water channels with junction to the heat-exchanger have only the connection to the water coolers in otherwise closed water circuits.
Increase in swept volume for 5.5-litre engine concept Cubic capacity No of cylinders
5500 Single cylinder volume
The crankcase below the main bearing centre line is manufactured identical to the R10 as complex, heavy-duty cast component – the so-called bedplate. Owing to directional solidification (Sophia® process) the precision casting has equally high strength (Rm 35 Mpa) and ductility. The minimum wall thickness is less than 2 mm. The dry sump’s side mounted scavenge port and ribbings connect the bearing blocks with one another. A very stiff unit is created together with the upper crankcase part. Engine and monocoque have thus almost the same stiffness. The main bearings are fastened with two bolts on each side. The four lower engine mounting/monocoque studs are connected to the gear wheel shaft and are braced by stiffeners to the main bearings.
Pressure and temperature sensor monitor the oil and water circuits. Increase in cylinder volume 20.00% 50.00%
Figure 8: Complete engine The complete engine, in
CAD format 4.2 Crankshaft drive
Owing to its design and construction as 10-cylinder, the crankshaft drive is subject to an unbalanced momentum. The crankshaft’s design considers several aspects: Bearing load through maximum ignition pressure, inertial forces Unbalanced momentums of the 1st and 2nd order Torsion and bending stiffness Minimum weight
a 5.5-litre V10 TDI engine demonstrated the 10-cylinder concept’s length advantage, but the V12 TDI could be installed lower in the car and achieves a lower height advantage, too. An eight-cylinder configuration was ruled out due to the high single cylinder capacity and the combustion process of the larger cylinders.’ Taking all this into account,
Picture 9: R15 TDI cylinder block The R15 TDI’s fully stressed, all-aluminium cylinder block
the format chosen for the new engine was a 5.5-litre V10 twin turbo diesel. Visually similar to the V12 used in the R10 TDI, the new engine was clearly based
Crankshaft (ignition sequence 1 – 6 – 3 – 8 – 5 – 10 – 4 – 9 – 2 – 7)
on the same concepts but with some clear differences – not least the number of cylinders. ‘When we made the V12 we effectively made a V10 too, so on this engine we changed the bore and stroke but the engine is actually not much different. The 90-degree cylinder bank angle was retained, since it represented the best compromise regarding torsional stiffness, overall height and c of g position for the R15 chassis. The resulting uneven angular ignition spacing for a crankshaft with continuous, single axis crank pins has no influence on the wider car. Some people say because it is a V10 perhaps a 75-degree bank angle would be more suitable, but this is a diesel. It’s not very high revving, so 90 degrees is just fine.’ The carry over from the V12 was clear to see in other areas too, including the cylinder spacing and the layout of the pump and camshaft drives.
CRANKCASE DETAIL ‘The fully stressed, all-aluminium alloy cylinder block was made using a low pressure sand casting method. Each of the 10 cylinders was coated with Nikasil to reduce wear and friction, while for piston
www.racecar-engineering.com • Le Mans 458.3 550
- 11 - 10
5500 8
687.5 -11.9%
5.5-litre V10 5.5 litre
Figure 7:
Development process of R15 V10TDI engine development 4. Engine design Change
The engine was designed with the following targets in mind: Compact dimensions High engine stiffness for low weight Very high mechanical durability High level of component integration Low number of exterior fittings and connectors
Capacity Configuration
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