In 1969, BMW won the European Touring Car Championship with Dieter Quester and the BMW 2002 TI, doing pioneering work and writing history in the process.
The first BMW Turbo in motor racing - the M121 - provided the necessary drive. After many more BMW Turbo engines in the 50 years since then, the newly-developed Class 1 regulation-compliant BMW P48 engine will make its debut in the BMW M4 DTM when this season’s DTM kicks off at Hockenheim (GER) at the start of May.
Times may have changed, but the outstanding properties of the engine have remained the same, BMW says.
Past and present
Despite the 50 years that lie between them, the two high-performance engines have a number of similarities: both are straight, four-cylinder engines with a two-litre capacity and a turbo charger.
In both the BMW M121 and the P48, the sensitive engine components must be protected by a heat shield from the heat emitted by the turbo charger. A mechanical injection pump supplies the engine with fuel in both cases.
The pressure with which the combustion air is supplied to the engine, though, can hardly be compared any more. With 0.98 bar of pressure, the first generation of turbo race engine achieved approximately 208kW at 6500 rpm. The exhaust fan was theoretically capable of developing a boost pressure of 1.76 bar. However, the pressure in the cylinder would have been so great, that the cylinder head would have lifted off.
Nowadays, boost pressures of up to 2.5 bar are possible with more than 448kW.
The crankcase and cylinder head were manufactured in a special sand-casting procedure in the BMW Landshut foundry. In the meantime, components like the ignition distributor, fan, wet sump and boost valve have since disappeared from the engine.
There is also no longer a direct charge air pipe, which supplies the engine with compressed air without any cooling. Instead, the P48 has a sophisticated dry sump system. The oil required for lubrication purposes within the engine is extracted immediately without any oil being lost through splashes. Another part of this system is the oil tank, which is directly attached to the engine. Efficient charge air cooling also allows for increased performance and efficiency.
Auxiliary units, like the starter and generator, are no longer on the engine, but are mounted on the transaxle gearbox behind the engine.
Carbon-fibre-reinforced plastic has replaced the old aluminium weld-and-cast construction on the plenum chamber. Furthermore, the butterfly is now moved electrically and no longer by a mechanical throttle rod. Instead of an open ignition harness, the electrical wires in the P48 are housed in a protective, carbon cable tray.
The P48 is one of the most efficient BMW race engines of all time. One of the key aspects of it is its exceptionally good consumption, BMW says.
As the DTM regulations limit the permitted fuel flow, every fuel saving means better performance and was followed in detail. Compared to its predecessor, which itself was very efficient, the current engine has been made almost 10 percent lighter on juice.
It is actually more than 50 percent more efficient than the M121 from 1969.
This was achieved with the help of the high-pressure direct fuel injection, as found in BMW production engines, as well as a mixture preparation and combustion - tried and tested in many simulations and tests - which allows the engine to operate in so-called ‘lean burn mode’.
A consistent minimisation of friction losses, such as through the aforementioned oil system and the use of high temperature-resistant components that do not require cooling by the fuel, make the P48 one of the most efficient BMW race engines ever.
KEY FACTS AND FIGURES ON THE M P48
* Type: Four-cylinder turbo engine with direct fuel injection
* Capacity: 1999cc
* Weight: 85kg (basic weight, according to regulations)
* Bore: between 86 and 90mm
* Engine speed: max 9500rpm
* Power output: More than 448kW
* Service life: More than 6000km (per season)
* Cylinder block and cylinder head made from cast aluminium in the BMW foundry in Landshut
* Steel crankshaft
* Four valves per cylinder, operated via rocker arm
* Steel camshafts, operated via gears
* High-pressure, direct injection, as with BMW production engines with 350 bar
* Dry sump lubrication
Despite the P48’s significant increase in power of about 74kW, the unit is designed for reliability and durability, and lasts roughly 6000 kilometres. The turbocharger supplies the engine with 400 litres of air per second - 3500 times as much as a human breathes and the pistons accelerate from zero to 100km/h in less than a thousandth of a second - 1200 times faster than a lunar rocket.
If you’d like to see the P48 in action be sure to tune into the DTM racing action this weekend.