So we start with a standard production car, fresh off
the dealers showroom floor, What do we do and how do
we do it, to turn a mass produced clone into a competitive
little weapon....
The Rally Car builder starts with 4 distinct objectives
in mind:
 Safety
Handling
Braking
Performance
 Now
for you true petrol heads out there you may well be
frowning already looking at performance being last on
the list, but think about this, the speed that you go
down the straight is determined by the exit speed from
the corner, in other words theres absoloutely no point
in having 500 horsepower if the car is a dog through
the bends and can't put its power on the ground, the
well sorted 200 hp car will nail it every time.
So let us examine each area.
Safety
The first item to be built into the car is a roll cage,
usually with a minimum of 6 anchorage points, sometimes
many more. This single item is probably the most important
of all safety items and, believe it or not crosses over
directly into the handling and performance catorgeries
as a well built, tight fitting roll cage not only can
save the occupants of the car from injury in the event
of an accident, but does wonders for the rigidity of
the shell, resulting in much better cornering ability
and that increase of speed down the straight......This
is then covered in high energy absorbing foam to protect
the occupants further.
Next on the list is proper seats.The function of these
is to properly locate the driver and navigator in the
vehicle, and keep them there, not only through the high
G force loadings of aggresive cornering, but also in
the event of an accident. New Zealand has some highly
talented builders of these sorts of seats, their constuction
ranges from a steel frame 'clubmans' type, to the 2.9
kilogram carbon fibre top of the range, custom upholstered
to clients requirements.
To help in the containment of occupants, full harness
aircraft type safety belts are added.These are of a
minimum now of 3" and are usually of 4 sometimes
5 anchorage points.Once these fully adjustable belts
are pulled down tight, with the occupants in autosport
seats, they simply cannot be thrown around at all.
Fire extinguishers, intercoms and the all important
'Terratrip" (high tech oddometer) are also added.
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 Handling
Now heres where it starts to get interesting.
Essentially a manufacturer builds what is known as Understeer
into a new vehicle, this in essence is the process of
the front end letting go under hard cornering and trying
to 'sledge' straight ahead.Understeer is deemed to be
more controllable than Oversteer which is the process
of the back end doing the same thing.
The first thing that the rally car builder aims for,is
to neutralise this understeer, along with drastically
improving the cars suspension as the shock absorbers
move through both compression and expansion.
Normally this is achieved by the replacement of both
springs - uprated to a higher rate, and shock absorbers,
there are many quality aftermarket brands available,
probably the best known of all are Bilstein and Koni,
these 2 brands have graced many a world rally championship
car.
 Whilst
we have already touched on the benefits of a good roll
cage, the fitting of braces between  suspension
mounting towers can have significant benefits for the
shells rigidity.
Upgraded suspension bushes in high tech plastics are
also added, or alternatively solid metal spherical bushes
for those getting particularly serious.
Steering geometry is also altered with the addition
of negative camber (pulling the tops of the wheels inwards)
and positive caster (pulling the front wheels forward,
similar to a bicycle fork), all in the interest of improved
cornering stability.
Larger diameter and width alloy wheels are added, along
with lower profile quality tyres to not only provide
for much increased airflow around the brakes (or indeed
much bigger brakes ), the widening of the cars track
which can have a huge effect on its cornering speeds,
and vastly increased grip and traction.
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Braking
 Generally
most late model production cars braking systems are
more than adequate, and for the rally car builder, generally
the replacement of brake pad materials with that of
a quality aftermarket item, that can withstand vastly
increased temperatures without turning to mush is all
that is required.
However for the serious competitor in the modified classes
the replacement of the complete system is required,
with the addition of bigger ventilated rotors and either
4 or 6 piston brake calipors (standard production cars
generally only have 1 ) the nett effect of these changes
is simply awesume! Braking distances are slashed.
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Performance
So we have the 3 other areas fully sorted, the car is
now very safe for the occupants, secured in a cocoon
of roll cage, strapped into fully form fitting seats
and ready to go in a car that now handles like it is
on rails and stops in no distance whatsoever, we're
wringing its neck but its got no go. Where to from here?
 Lets
look at what we can change externally to increase performance
first.
The best place to start is the aircleaner and air box,the
replacement of these 2 items alone with quality, free
breathing aftermarket options is worth considerable
horse power gains (6 hp on a Suzuki (Maruti ) Baleno
).
Next on the list is the exhaust.The removal of the restrictive
manufacturers manifold and tailpipe and replacement
with tuned length extractors and free flowing, bigger
diameter tailpipe can be worth as much as a 10% increase,not
only at maximum rpm,but depending on lengths and diameters,right
throughout the rev range.
Quality spark plugs of a cooler operating range, as
well as ignition leads will also help.
With the likes of the Baleno, that has computerised
electronic fuel injection big horse power gains are
available with the replacement of the factory e.c.u
(computer ) with a programable aftermarket computer.
The 'mapping' of fuel/spark to optomise both for maximum
burn is well worth the money.
Lightening the flywheel allows the engine to rev up
quicker and freer.
Now lets look inside;
The best place to start is the gearbox. Generally a
manufactures gear ratios leave a lot to be desired with
them having too low a 1 st gear, and a big gap between
2nd and 3rd gear.
The fitting of aftermarket gears can close the ratios
right up which means that the driver can keep the car
right up in its maximum power developing range without
having to worry about it falling flat on its face everytime
he changes gear, be prepared for a car with a big tall
1st gear though!
Changing the differential ratio to a lower one helps
no end as well, letting the engine pull the car easier
and closing up the gaps between the gears. The sacrifice
here is a reduction in top speed, although often this
is negated by the fact that the engine now can rev harder
and free'er due to the aformentioned modifications that
have already been performed.
Next comes cylinder head modifications, with the flowing
and removal of 'obsticals' that can inhibit the travel
of both the unburnt air/fuel mixture, along with the
the burnt exhaust gases. This is known as 'porting'
and,is usually accompianied by the addition of larger
valves in the head .
Along with this comes reprofiling of the camshafts,changing
the amount of time that gases are allowed to enter and
exit the cylinder head. The net effect of these 2 modifications
can be massive, especially when complemented by every
thing previously mentioned.
Lighter forged pistons with smaller rings to reduce
internal drag can be added, and are generally necessary
at revs exceeding 8000 rpm.
So now you've probably added another 60 to 100 plus
%horsepower to your car, depending on how much you want
to spend, LETS GO RALLYING !
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