Although F1 racing engines have lost some of the attractiveness they
used to have when the regulations allowed more freedom, every single
design currently in use is still a highly advanced piece of engineering
that has required lots of time and thought. An engine is the only power
source of a Formula One car - apart from the KERS systems in 2009 which
are indirectly charged by the power generated by the engine - and is a
structural part of the chassis.
Facts and figures
Because
of the regulations and engineering optimisations, all curent engines
are of a similar type, and feature the following similarities:
- All F1 engines are naturally aspirated V8's of 2400cc
- Engines are limited to 18,000rpm
- The weight is exactly 95kg (each manufacturer easily reaches this regulated minimum weight)
- Engine blocks are constructed of forged aluminium alloy, because
of the weight advantages it gives in comparison to steel. Other
materials would maybe give some extra advantages, but to limit costs,
the FIA has forbidden all non-ferro materials.
- Crankshaft and piston rods are Iron based for strength.
- At its maximum pace the current V8 engines consume around 60 litres of petrol for 100km of racing.
- It's not exactly known how much oil such a top engine contains,
but this oil is for 70% in the engine, while the other 30% is in a dry-sump lubrication system that changes oil within the engine three to four times a minute.
- Before its first track time and after each race, each engine is tested on an engine dyno to validate its performance and identify problems. A videoclip of Renault's RS24 on the dyno can be found here.
Evolution of engine design
All current engines run by the competing F1 teams are very similar
due to the very stringent regulations that have increasingly come into
play since 2006. Until that time, all car manufacturers involved in F1
were effectively outracing each other in a spending race. It is not a
lie to claim that in the years after 1995, the manufacturer who invested
most and could hire most people could produce the best engine.
Back in 1997, Ford Cosworth started a furious battle for weight
reduction as their CR1 at the time was at least 25kg lighter than any
other.
Although they
suffered some reliability problems troughout the season, the engine was an example
for the others, as it allowed the team to shift ballast in the car to benefit the car's handling.
As a reaction to this weight shedding, the the 1998 Mercedes-benz
engine
was possibly one of the most revolutionary engines ever built, making
performance gains and drastic weight cuts at the same time. It quickly
proved good enough to be the basis of Mika Hakkinen's two consecutive
world titles with McLaren Mercedes. When in 2000, the FIA decided to
limit the use of Berillium alloys - to a maximum of 5 mass percentage -
due to being poisonous in high quantities, Mercedes struggled for years
to recover from that setback - they could not match anymore the power of
the at that time mighty Ferrari and BMW engines.
By the end of 2005, most of the teams had converged their designs to 3
litre V10's with an internal angle of 90°. The teams' designers had
come to the conclusion that 90° was the best compromise between
performance and stiffness of the engine itself.
That same year, some 3l V10 engines were producing more than 980hp
and running very close to the 1000hp mark, a figure that was never
reached since the ban on turbo engines. It was a sign for F1's governing
body to change the regulations as top speeds at Monza of 370km/h were
deemed hazardous for the drivers as well as the spectators. The maximum
capacity was thus reduced to 2.4l and the cylinder count to 8.
Additionally, the FIA ruled that an engine freeze would come into
effect a year later to put an end to the spending race.
Only 2 years later however, halfway through 2008, the FIA and
several teams who strictly followed the rules - including the likes of
Toyota and Renault - found that the regulations still allowed too much
freedom. It appeared that over the last year, Mercedes and Ferrari had
been able to add up to 40hp to their engines as so called "reliability
updates", while others had followed the engine freeze more strictly.
Several meetings with FIA officials and the teams' principals then
resulted in an equalisation of the engines, in which the less powerful
could put on several updates to be on par in the next years.
Even so, without fiercely looking for improvements, a current F1
engine is a highly interesting piece of engineering, in total consisting
of 5000 seperate parts, 1500 of which are moving. It is estimated that
when in operation, a new F1 engine can produce around 720hp, but would
be able to reach up to 780hp and above 20,000rpm if there would not be a
limit on engine revolutions.
Difference with road engines
- Higher volumetric efficiency. VE is used to
describe the amount of fuel/air in the cylinder in relation to regular
atmospheric air. If the cylinder is filled with fuel/air at atmospheric
pressure, then the engine is said to have 100% volumetric efficiency.
Turbo chargers for instance can increase VE to above 100% while normally
aspirated engines tipically run anywhere between 80% and 100%. In this
region however, a Formula One engine usually can achieve a higher VE
than normal road engines because of their highly optimised intake
manifolds.
- Unfortunately, from the total fuel energy that is put into the
cylinders, averagely less than 1/3 ends up as useable horsepower.
Ignition timing, thermal coatings, plug location and chamber design all
affect the thermal efficiency (TE). Low compression
street engines may have a TE of approximately 0.26, a racing engine may
reach approximately 0.34. This seemingly small difference results in a
difference of about 30% (0.34 - 0.26 / 0.26) more horsepower than
before.
- From all that power generated, part of it is used by the engine to
run itself. The left over power is what you would measure on a
dynamometer. The difference between what you would measure on the dyno
and the workable power in the cylinder is the mechanical efficiency
(ME). Mechanical efficiency is affected by rocker friction, bearing
friction, piston skirt area, and other moving parts, but it is also
dependent on the engine's RPM. The greater the RPM, the more power it
takes to turn the engine. This means limiting internal engine friction
can generate a large surplus in power output, and where in F1 the stress
is on power, on the road it is also on fuel consumption.
These main optimization necessities are what makes Formula One engine
design difficult. At the end of the line, an F1 engine revs much higher
than road units, hence limiting the lifetime of such a power source. It
is especially the mechanical efficiency that causes Formula One engines
to be made of different materials. These are necessary to decrease
internal friction and the overall weight of the engine,
but more importantly, limit the weight of internal parts, e.g. of the
valves, which should be as light as possible to allow incredibly fast
movement of more than 300 movements up and down a second (this at 18.000
rpm).
Another deciding point trying to reach a maximum of power out of an
engine is the exhaust. The minor change of lenght or form of an
exhaust
can influence the horsepowers drastically. Although variable outlet
systems are not allowed, the exhaust system on a race car does not
feature a muffler, lacks a katalysator and is specially made to
whitstand temperatures as high as 1200°C, a lot more than what is
achieved with a regular road engine.
Engine design phylosophies
Considering internal combustion engines (thus leaving out oscillating
and Wankel rotary combustion engines), there are basically three
different ways of building an engine. The difference here is how the
cylinders are placed compared to each other.
- Inline engines, where all cylinders are placed next to (or after)
each other are not used in Formula One since the 60's. While the engines
are small, they are long and therefore require a heavy cranckshaft.
- Boxer engines are actually one of the best ways to build an
engine, if all external factors allow it. Two cylinder rows are placed
opposed to each other. You could consider a boxer engine as being a 180°
V-angle engine design. These engines became popular in F1 because of
the low centre of gravity and the average production costs, but later on
disappeared out of the picture as this type of engine is not
sufficiently stiff enough to whitstand the car's G-forces in cornering
conditions. Ferrari for instance have run 12 cylinder boxer engines from
1970 to 1980 before moving to a 120° V-angle engine.
- V-type engines, as currently used in all F1 cars. The V is in fact
the geometrical angle that seperated the two cylinder banks from each
other where the crankshaft can be considered the origin of the angle.
Obviously for this type of engine the size of the V is a major factor
and must be decided in the first phases of the engine design.
Previously, engines have been designed with angles such as 60° V12 or
72° V10. Although it has historically been an interesting evolution to
see the differences between the teams' engines, the FIA have fixed the
engine type to 90° V8 models.
Since the introduction of the Ford Cosworth DFV, an engine in a F1
car is a stressed member of the chassis, meaning that it is an integral
part of the car. Before that idea, a chassis was built as a tube frame
with the engine placed in it afterwards, while now a chassis would fall
apart if no engine was fitted. A current engine is bolted in between the
rear end of the monocoque and the frontal side of the gearbox. As of
that time, V-type engines have gradually pushed out any other engine
type because they are compact and can be constructed very rigidly
without requiring further strengthening to the chassis to ensure
stiffness.
Contrary to boxer or flat engines, V-angled combustion engines pose
an extra design problem, as it is crucial for an engine's performance
that the V-angle is chosen wisely. This angle important to ensure a
correct firing sequence and hence also influences its primary balance.
Calculating possible V angles for a specific number of cylinders is
fortunately not a daunting task. If you consider that every combustion
cycle takes 2 turns - intake and combustion phase - of the crankshaft,
and a full circle is 360°, the engine's included V-angle x the number of
cylinders must be
a function of 720 in order to achieve evenly spaced cylinder firing
and primary
balance.
That is also why a boxer engine is an ideal layout. The cylinders are
opposed at
180° so having 2 or 4 or 6 or 8 or 10 or 12 isn't that big. Perfect
primary balance is easy to achieve, as long as the reciprocating and
rotating
parts are in balance and, the firing order is always evenly spaced. A
few examples make it clear why several specific angles have been very
popular in F1 engine design:
- As mentioned earlier, Ferrari have used a 60° V12 or 120° V12
engine. As for the first option, divide 720° by 12 cylinders and you get
60. You get 120° when you imagine a V12 as two aligned V6 engines.
- Renault's extremely successful 72° V10 engines share the same
thoughts. It is the perfect bank angle for any V10 engine if a boxer is
not an option. One cylinder is fired every time the cranckshaft has
completed 72° so that after 2 turns every single piston has gone through
one complete cycle.
- Currently every team runs 90° V8 engines but not only because the
regulations prescribe so. Also this is a perfect angle and meets the
size requirements set by the aerodynamicists.
Contrary
to these optimal choices, there have also been unusual uses. For
instance the 2005 90° V10 engines that everyone but Renault were using.
While they may have been more interesting for other reasons, it's
performance could theoretically not beat Renault's RS25 that was a 72°
V10. The 90° V10 engines hence had either offset crankpins or a funny
firing order.- Before their RS24 Renault was trying a revolutionary design as
they designed a 112° V10. Although the engine evolved from RS21 to RS23
and was beneficial in terms of the centre of gravity it was finally
abandoned. The engine could not reach competitively high rpms since the
uneven firing order introduced unwanted vibrations in the engine.
Cranckshaft design
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 requirements. The V8 has a distinct
firing sequence and demands a fundamentally different crankshaft
design. Whereas a 72-degree offset crankshaft was used in most V10
Formula One engines, V8 powerplants can feature crankshafts with either
four throws spaced at 90 degrees or four throws spaced at 180 degrees.
Standard production engines 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.
Cooling
With such a low thermal efficiency, cooling of any internal
combustion engine is vital for its correct operation. Basically, an F1
cooling system is the same as in any regular road car, as engine cooland
and oil is pumped through a radiator to cool down before completing
another cycle through the engine.
However, due to the space restrictions and aerodynamic requirements
of a race car, the positioning of these components is completely
different. The following shows the internals of a championship winning
Renault R25
of 2005, included with its Renault RS25 engine (2). The flat
panels located nearly vertically in the front of the side pods are the
radiators (4). While in this picture the radiator is covered with a
protective hose, it is not during running as air passes through the
aluminium fins of the radiator. Their position however varies
considerably in different cars as they are influenced by the aerodynamic
and weight distribution requirements of a car.
Contrary to popular belief, the air inlet above the driver's head is
not part of the cooling system but instead provided the engine's
cylinders with air to be mixed with fuel for combustion. It is commonly
thought that the purpose of this is to 'ram' air into
the engine like a supercharger, but the
airbox does
the opposite.
The carbon fibre duct (1) gradually
widens out as it approaches the engine, effectively creating a venturi
and a suction effect on the small air inlet. The shape of this ducts
and inlet however must be carefullly designed to both fill
all cylinders equally and not harm the exterior aerodynaimcs of the
engine cover,
all to optimize the volumetric efficiency.
Marked with (3) is the
engine exhaust system while (5) and (6) identify the rear suspension that is fitted onto the gearbox.
Transmission
The transmission of any car is considered to be all intermediate
gears and systems to get the engine rotational power to the wheels. In
reality this comes down to the gearbox and differential, which are both
assembled into the gearbox casing. Just as with the engine, this casing -
often made of titanium or carbon fibre - is also a structural part of
the chassis and is firmly bolted onto the rear end of the engine. More
can be found in the specific
article about F1 transmissions.
Regulations
The current regulations on Formula One engines can be summarised as
follows. These specifications have become more strict during recent
years in an attempt to limit costs and decrease performance. You can
find an
evolution of the most important regulations per era in the
safety section.
As this is only an exerpt of the most important regulations on engines,
you would need to see the official FIA technical regulations before you
start to design a Formula One engine yourself.
Specification
Only 4-stroke engines with reciprocating pistons are permitted.
Engine capacity must not exceed 2400 cc.
Crankshaft rotational speed must not exceed 18,000rpm.
Supercharging is forbidden.
All engines must have 8 cylinders arranged in a 90º “V” configuration and the normal section of each
cylinder must be circular.
Engines must have two inlet and two exhaust valves per cylinder.
Only reciprocating poppet valves are permitted.
The sealing interface between the moving valve component and the stationary engine component must be
circular.
Dimensions, weight and centre of gravity
Cylinder bore diameter may not exceed 98mm.
Cylinder spacing must be fixed at 106.5mm (+/- 0.2mm).
The crankshaft centreline must not be less than 58mm above the reference plane.
The overall weight of the engine must be a minimum of 95kg.
The centre of gravity of the engine may not lie less than 165mm above the reference plane.
The longitudinal and lateral position of the centre of gravity of the engine must fall within a region that is the
geometric centre of the engine, +/- 50mm. The geometric centre of the engine in a lateral sense will be
considered to lie on the centre of the crankshaft and at the mid point between the centres of the forward
and rear most cylinder bores longitudinally.
Variable geometry systems are not permitted
Materials
Magnesium based alloys, Metal Matrix Composites (MMC’s) and Intermetallic materials may not be used anywhere in an engine
Coatings are free provided the total coating thickness does not exceed 25% of the section thickness of the
underlying base material in all axes. In all cases the relevant coating must not exceed 0.8mm.
Pistons must be manufactured from an aluminium alloy which is either Al-Si ; Al-Cu ; Al-Mg or Al-Zn based.
Piston pins, crankshafts and camshafts must be manufactured from an
iron based alloy and must be machined from a single piece of
material.
A supplementary device temporarily connected to the car may be used to start the engine both on the grid
and in the pits.
source: http://www.f1technical.net/articles/4
