Revolution not evolution for the BMW P86 engine
Revolution, not evolution: the Formula One World Championship will not just be welcoming new engines to the fray in 2006, but a whole new generation of engines. Thanks to a change on the regulations, the new V8 units with 2.4-litre displacement replace the 3.0-litre V10 powerplants which ruled the roost last year. Heinz Paschen, the Munich-based Technical Director responsible for the entire powertrain of the new F1 car, gives us a glimpse of what to expect: "The new V8 engines are shorter and, with displacement reduced by 600 cc, have lower output and fuel consumption. However, they are no lighter, cheaper or less complex than their ten-cylinder predecessors."
Although the V8 with the now compulsory cylinder angle of 90 degrees may look like a sawn-off V10, technically it is an entirely separate concept with its own specific characteristics. The V8 has a distinct firing sequence and requires a fundamentally different crankshaft design. Whereas a 72-degree offset crankshaft was used in BMW's V10 Formula One engine, V8 powerplants can feature crankshafts with either four throws spaced at
90 degrees or four throws spaced at 180 degrees. Standard production cars are fitted with 90-degree crankshaft variants due to their better dynamic attributes, but a 180-degree crankshaft is favoured in racing-car engine design. The improved performance this allows offsets the disadvantages in terms of dynamics.
As a rule, we can expect the new V8 engines to have around 20 percent less power than their V10 predecessors and 20-percent smaller radiators - both reduced in proportion to the lower displacement.
In addition to the inherent differences in the design of a V8 engine, numerous other specification details contained in the new regulations have sent the engineers back to the drawing board.
Lightweight construction principles have taken centre stage. The new V8 has to be heavier than its predecessor, even through the 2005 engine had two extra cylinders. This season's powerplants must tip the scales at no less than 95 kilograms. This should include the intake system up to and including the air filter, fuel rail and injectors, ignition coils, sensors and wiring, alternator, coolant pumps and oil pumps. It does not include liquids, exhaust manifolds, heat protection shields, oil tanks, accumulators, heat exchangers and hydraulic pump.
Added to which, the new regulations stipulate that the engine's centre of gravity must be at least 165 millimetres above the lower edge of the oil sump. The experts had previously managed to lower the ten-cylinder engine's centre of gravity to the benefit of the car's handling. However, the longitudinal and lateral position of the V8's centre of gravity has to be in the geometric centre of the engine (+/-50 millimetres). For the technical commission, checking that everything is in order no longer consists of a simple weighing process. Now, making sure that the rules have been observed involves weighing on two levels and making calculations according to the lever principle.
Previously a closely guarded secret, the dimensions of the cylinder bore are now limited to a maximum 98 millimetres. The gap between the cylinders is also set out in the rulebook - at 106.5 millimetres (+/- 0.2 mm). The central axis of the crankshaft must not lie any less than 58 millimetres above the reference plane.
Another critical change in the regulations is the ban on variable intake systems. Known as "trumpets", these systems could previously be used to optimise the car's torque curve. The fixed duct lengths will now make achieving good engine driveability a more exacting challenge. "The teams will have to devote a lot more time and effort to this area", confirms Paschen. "We have to strike a compromise between maximum power and good driveability." Where the best compromise for the pipe lengths is to be found depends on various factors. The track layout and the weather, for example, both play a role. The teams will favour one set of intake pipe lengths for circuits with long straights - like Monza, Indianapolis and Spa - where power is critical, and a different selection for twistier grand prix tracks such as Budapest and Monaco, where driveability relegates raw power to the back seat. The same applies to different weather conditions. Joining variable intake systems on the black list are variable exhaust systems and variable valve control systems.
The power supply to the engine electrics and electronics is limited to a maximum 17 volts and the fuel pump now has to be mechanically operated. Only an actuator may now be used to activate the throttle valve system. With the exception of the electric auxiliary pumps in the petrol tank, all sub-components must now be driven mechanically and directly via the engine.
"Sensibly, a long list of exotic materials have been excluded", says Paschen in reference to another chapter of the regulations. "Now we are all working with the conventional titanium and aluminium alloys stipulated in the regulations."
That means there are now fewer differences in the technical make-up of the various manufacturers' engines. However, this does not mean that the challenge for the engineers has been in any way diluted. As Paschen explains: "It's all about who can find the best solution within the framework of the new rules in terms of thermodynamics and mechanical dynamics."
Indeed, mechanical dynamics and vibrations represent a particularly critical area of development for the new generation of Formula One engines. The V8 units have different firing sequences and intervals from their V10 predecessors, which leads to a totally different situation in terms of vibrations. The V10 entered a critical area between 12,000 rpm and 14,000 rpm. However, this was not an issue as the engine did not spend much time in this rev band and smoothed itself out again once the driver stepped up the revs. And, since the upper rev band was where it spent the majority of its time, vibrations were not a worry. A V8, on the other hand, is not so well off. Its vibration curve enters critical territory later than the V10 - from approximately 16,000 rpm - and continues to climb from there.
It's therefore no longer possible to think in terms of getting through a difficult patch and everything will be all right. Now, the problem of constantly increasing vibrations has to be confronted head on. "If you don't get a handle on vibrations", says Paschen, "they will eat into the service life of the engine and multiply the loads exerted on chassis components. In order to get on top of this problem, the calculation and analysis of each individual engine component has to be totally reliable. However, analysis of the individual components is only part of a larger challenge. Determining how they work with and against each other in simulations of the overall system is the main task."
Regarding the costs involved in the changeover from V10 to V8, Paschen pulls no punches: "The manufacturers had a deep well of experience with the V10 concept and that helped to keep development costs down. The expense involved in developing a whole new unit, though, is huge. At least in the initial development phase for the V8, a relatively small reduction in cylinders has meant a relatively large hike in costs."
at the 740bhp from a 2.4 liter engine
a problem to the sport as Max is.
