|
|||||||||||||||||||||||||||||||||||||||||||||
| TECHNICAL ARTICLE 001 Reynard Formula 4000, Powered by Holden vs. Holden Commodore VZ Executive Formula 4000. Australia's most technically advanced circuit racing cars. These cars represent the forefront of technology and epitomise the term "state-of-the-art". The cars can get around a racing circuit faster than anything else in Australia. Not quite the same as your family sedan, are they? Or are they.... This technical article - thanks to ozboss.net - will compare a typical family sedan - a Holden Commodore VZ Executive, with a Reynard 94D Formula 4000.
The Alloytec also features continuously variable valve timing. This means the timing of the camshafts is adjusted for the rpm range the engine is operating in. In the old days, an engine would be fitted with a performance cam to improve power, and smoothness at idle would be sacrificed. The so-called "lumpy cam" could not provide a smooth idle and high power output. With the Alloytec's variable cam timing, we have the best of both worlds. At idle and low rpm, the cam timing is adjusted for smoothness and driveability. At higher rpm, the cam timing is adjusted for maximum power output. The road-going engine also features Electronic Throttle Control -
matching the driver's intentions with the capacity and actions of
powertrain components. For the Formula 4000 engine,
The Formula 4000 engine is also fitted with a larger throttle body, allowing more air into the engine, and consequently higher power output. Other modifications to the racing version include fitment of a dry sump (to avoid oil surge at very high cornering loadings), and the use of a control MoTeC Engine Control Unit (the brain of the engine). Final Result - Power Output:
The Commodore Executive model is fitted with a four speed automatic transmission. The ratios are pre-selected by Holden, and whilst manual-ised shifting is an option, the gear shift is ultimately determined by the software in an electronic control module. The automatic is a smooth gearbox, perfectly suited to taking passengers from a to b. The Reynard Formula 4000 is fitted with a five speed, sequential shift, dog engagement gearbox. The gearbox can be customised with an almost infinite number of ratios, as selected by the team or driver. This allows the gears to be perfectly matched to the circuit, using every last rpm the engine has to give. The gears are straight cut to minimise friction losses, but this approach also maximises transmission whine. The dog engagement means the gears are not automatically synchronised to match speed on gearchanges, which means the driver must be forceful and precise when changing gears. The gear selection process is assisted by the sequential shift mechanism, making it difficult for the driver to miss, or skip, a gear.
Final Result - Transmission:
The Reynard Formula 4000 is fitted with four wheel disc brakes. Each fully floating disc is made from cast iron, and is ventilated, and each caliper features four pistons. The brakes are actuated via a separate master cylinder for the front and rear - the bias between the two can be adjusted by the driver. All four brake discs have cooling air directed to them by carbon-fibre brake ducting. The pads are heat sensitive, and do not provide optimum braking efficiency until at normal operating temperature. Final Result - Braking:
The Reynard Formula 4000 is fitted with 13" x 11" front wheels,
and 13" x 15" rear wheels. All wheels are constructed of magnesium
alloy, and all four wheels combined weigh approximately the
The Commodore uses a MacPherson strut front suspension setup, with Control Link independent rear suspension. This provides a comfortable ride, and good road holding qualities. The Formula 4000 features double wishbone suspension front and rear, with triple adjustable Dynamic gas dampers, and pushrod activated coil springs. The pushrod setup allows the springs to be mounted flush to the body, and keeps them out of the airflow, reducing drag. The suspension setup is extremely stiff - around 50 percent of the travel is in the tyre. The geometry, spring stiffness and shock valving is tailored to provide the optimum balance between mechanical grip, and aerodynamic stability (by keeping the car as level as possible). Final Result - Cornering:
The Reynard Formula 4000 features composite technology -
primarily carbon-fibre, with some kevlar thrown in. The chassis is a
monocoque design, centering around a carbon-fibre tub. The engine is
mounted
The Formula 4000 is not luxurious. The one concession to driver
comfort
The Commodore features a body shape designed to be aerodynamically efficient and to produce a minimum amount of lift. The body shape is also designed to keep wind noise to a minimum. The Formula 4000 is wind-tunnel designed with one purpose. To provide the optimum balance between downforce and drag. Each part of the car is considered to maximise the downforce levels, and increase the high speed cornering capacity.
Final Result - Capacity:
Final Result - Weight:
Overall, the Holden Commodore VZ Executive does the job it was designed to do to a very high standard. It can carry a family in comfort, safety and style. The very capable Alloytec V6 provides ample power, the four speed automatic is smooth and easy to use, the four wheel disc brakes with ABS technology provide good braking capability and the wheel and tyre combination provides grip wet or dry. On a racetrack however, the Reynard 94D Formula 4000 really comes into it's own. The racetrack is where it was born to be. It combines excellent power with low weight, tremendous grip, and aerodynamic downforce to propel itself around the circuit. Final Result - Laptime - Wakefield Park:
|
First
off, we'll start with the engine. And it's no accident that we're
starting here, because, believe it or not, both these cars share the
same engine. Holden's 3.6 litre V6 Alloytec is described as "one of
the most sophisticated and advanced production engines ever
manufactured in Australia", which makes it the perfect choice for
the family Commodore, and provides an excellent platform for a
Formula 4000 race engine. 
The
Alloytec features double overhead camshafts, which allows four
valves to be used per cylinder, and for the geometry of the valves
to be optimised for unimpeded airflow. This means the efficiency of
the engine is maximised, and power-to-displacement ratio is quite
high.
Electronic
Throttle Control is disabled (as it would count as an artificial
driver aid).
The
Commodore Executive transmits it's power from the engine to the
automatic gearbox via a flex plate and torque convertor - about the
size of a large saucepan. The Formula 4000 on the other hand uses as
small a diameter flywheel as possible to allow the engine to sit as
low to the ground as possible, and to reduce power sapping
rotational inertia. The flywheel is around the size of a small
plate, and has a tapered ring gear to allow the starter motor to do
it's thing. The clutch (pictured) is very similar to the clutches
currently used in Formula 1 - it is an AP Racing carbon clutch, and
is about the diameter of a compact disc.
The
Commodore VZ Executive is fitted with four wheel disc brakes. The
front discs are ventilated, and each caliper features two pistons.
The Commodore's braking performance is enhanced by the standard
inclusion of Anti-lock Braking System (ABS), Electronic Brakeforce
Distribution (EBD) and Brake Assist (BA). Each of these items
combine to take the driver's input to the pedal, feedback from each
wheel,
and use a computer to apply the optimum pressure to each brake disc.
The
Commodore VZ Executive is fitted standard with 15" x 6" steel wheels
(larger alloy wheels are an option). These wheels are shod with
205/65 R15 tyres, with a tread grooved to optimise water extraction
in wet conditions.
same
as one steel Commodore wheel fitted with it's tyre. The wheels are
shod with slick Avon tyres - 220/55 ZR13 at the front, and 320/45
ZR13 at the rear. 
The
Commodore VZ Executive features an all steel, four door body, on a
steel chassis. Some panels like the bumpers utilise plastic
technology. The interior features sound-proofing, carpet and various
trims to isolate the passengers from the noise of the road as much
as possible. The design of the body also incorporates
'crumple-zones', designed to absorb some of the shock in the event
of an accident.
directly
to the rear end of the tub, and is a stressed member of the car. The
front suspension, wing and other bodywork mount directly to the tub.
At the rear, the gearbox (bolted directly to the engine) provides
mounting for the rear wing and suspension. The design of the car
features the equivalent of 'crumple zones' - the nosecone at the
front, the sidepods, and the rear wing mount, all provide crush
sections to absorb some of the shock in the event of an impact.
The
interior of the Commodore is quite luxurious. Ergonomically padded,
fully-adjustable seats, climate control, a CD player all mean the
Commodore can comfortably accommodate five large adults. The
inclusion of air bags, and seat-belt pre-tensioners mean the
passengers also travel in utmost safety.
is
the custom-made foam seat insert - hugging the drivers body to keep
him perfectly in place. The seat insert does not extend past the
lower back however, and the driver sits with his bottom firmly
against the floor of the car - around 3 centimetres from the road
surface. The cockpit can barely accommodate just one person, and is
an extremely tight fit. Safety features include 3-inch, 6-point
harness and a HANS device (Head And Neck Support). All controls are
placed within easy reach of the driver.