Register a free account today to become a member!
Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!

Homologation rules!

Art. 254
Specific Regulations
for Production Cars
(Group N)

Last update April 2000


Large scale series production touring cars.


At least 2500 identical units must have been produced in 12 consecutive months and homologated by the FIA in Touring Cars (Group A).

The Supply Variants (VF) homologated in Touring Cars (Group A) are also valid in Production Cars (Group N).

The Optional Variants (VO) of the Touring Cars (Group A) form shall not be valid in Production Cars (Group N), unless they refer to:

- fly-wheel for automatic gearboxes ;

- fuel tank ;

- automatic gearboxes ;

- sun roof ;

- safety rollcage ;

- seat supports and anchorages;

- safety harness mounting points;

- 2/4 doors versions.

The use of tanks homologated in VO on the Touring Car (Group A) form must be carried out under the conditions laid down in article 5.9.2 of the Touring Car (Group A) regulations, and article 254.6.8.

Evolutions of the type (ET), kit variants (VK) or sporting evolutions (ES) homologated in Touring Cars (Group A) are not valid in production Cars (Group N).

Nevertheless, evolutions of the type and the sporting evolutions homologated, as from 01.01.97 in Group A, are valid in Group N.


Cars must have at least four places, in accordance with the dimensions defined for Touring Cars (Group A).


All the modifications which are not allowed by the present regulations are expressly forbidden. The only work which may be carried out on the car is that necessary for its normal servicing, or for the replacements of parts worn through use or accident. The limits of the modifications and fittings allowed are specified hereinafter. Apart from these, any part worn through use or accident can only be replaced by an original part identical to the damaged one.

The cars must be strictly series production models identifiable by the homologation form data.


Cars must have at least the weight appearing on the homologation form plus the weight of the safety devices

As far as rollcages which cannot be removed from the car and which were manufactured in accordance with articles 253.8.2 and 8.3 of Appendix J are concerned, the following weights will be taken as a basis:

- Rollcage according to drawings 253-3/4: 30 kg

- Rollcage according to drawings 253-5 to 17C: 35 kg

- Rollcage according to drawing 283-5: 45 kg

This is the real weight of the empty car (without persons or luggage aboard) without tools, jack. All the liquid tanks (lubrication, cooling, braking, heating where applicable) must be at the normal level foreseen by the manufacturer, with the exception of the windscreen wiper or headlight wiper, brake cooling system, fuel and water injection tanks, which shall be empty. Additional headlights which do not appear on the homologation form must be removed before weighing.


6.1 - Engine

-The accelerator cable may be replaced or doubled by another one regardless of whether it comes from the manufacturer or not.

- Ignition: The make and type of the spark plugs, rev. limiter and high tension leads are free. The ignition components in the electronic control unit are free. Sensors and actuators on the input side must be standard, as must their function.

- Cooling system: The thermostat is free as is the control system and the temperature at which the fan cuts in. Locking system for the radiator cap is free.

- Carburettors: The original system must be retained. The components of the carburettor which control the quantity of petrol entering the combustion chamber may be modified, provided that they do not have any influence over the quantity of air admitted.

Replacement air filter cartridges are accepted in the same way as the original ones.

- Injection: The original system must be retained. Components of the injection system situated downstream of the air-flow measuring device, and which control the quantity of petrol entering the combustion chamber may be modified but not replaced, provided that they do not have any influence over the quantity of air admitted. The interior of the electronic control unit for the injection is free. Inputs to the electronic control unit (sensors, actuators, etc.), including their function, must remain as standard. Outputs from the electronic control unit must retain their original functions in accordance with the homologation form.

The flow rate of injectors may be modified, but not their operating principle nor their mounting.

Replacement air filter cartridges are accepted in the same way as the original ones.

- Lubrication: The fitting of baffles in the oil sump is authorised.

Replacement oil filter cartridges are accepted in the same way as the original ones.

- The material of the elastic part of the engine mountings is free, but not the number of engine mountings.

- Exhaust: It will be possible:

. either to remove the inside of the original silencer ;

. or to modify the exhaust from the first silencer to the exit, the maximum dimensions of the duct being those of the pipe situated upstream of the first silencer (see drawing 254-3). Should two inlets exist in the first silencer, the section of the modified duct must be less than or equal to the total of the two original sections. Only one pipe may be present at the exit, unless the original part is used. The exit should be situated in the same position as that of the series production exhaust system.

These liberties must not entail any bodywork modifications and must respect the laws of the country in which the event is run with regard to noise levels.

Additional parts for the mounting of the exhaust are authorised.

A muffler is a section of the exhaust system that must reduce the exhaust noise level of the vehicle.
The cross section of the muffler must be at least 170% of that of the inlet pipe and contain sound deadening material. The sound deadening material may take the form of a 45% perforated tube or synthetic packing.
The length of the muffler must be between 3 and 8 times the inlet diameter.
The muffler may be supplied as a series part welded to a pipe but the pipe is not considered as part of the muffler.
If it is fixed directly onto the manifold, the catalyst may be replaced with a conical part of the same length and with the same inlet and outlet diameters. After this part, the exhaust will be free with a tube diameter no greater than that of the outlet from the catalyst.

The catalytic converter is considered as a silencer.

- Cylinder head gasket: The material is free, but not the thickness.

- Cruising speed controller: This controller may be disconnected.

- In rallies only:

The number of cylinders is limited to 6. The cubic capacity is limited as follows for normally aspirated engines:

. 3 l maximum for two valves per cylinder.

. 2.5 l maximum for more than two valves per cylinder.

In the event of supercharged engines being used:

The nominal cylinder capacity is limited to 2500 cm3 maximum.

The supercharged system must comply with that of the homologated engine.

All supercharged cars must be fitted with a restrictor fixed to the compressor housing. All the air necessary for feeding the engine must pass through this restrictor which must respect the following:

The maximum internal diameter of the restrictor is 32 mm, maintained for a minimum distance of 3 mm measured downstream of a plane perpendicular to the rotational axis situated at a maximum of 50 mm upstream of a plane passing through the most upstream extremities of the wheel blades (see drawing 254-4).

This diameter must be complied with, regardless of the temperature conditions.

The external diameter of the restrictor at its narrowest point must be less than 38 mm, and must be maintained over a distance of 5 mm to each side.

The mounting of the restrictor onto the turbocharger must be carried out in such a way that two screws have to be entirely removed from the body of the compressor, or from the restrictor, in order to detach the restrictor from the compressor. Attachment by means of a needle screw is not authorised.

For the installation of this restrictor, it is permitted to remove material from the compressor housing, and to add it, for the sole purpose of attaching the restrictor onto the compressor housing.

The heads of the screws must be pierced so that they can be sealed.

The restrictor must be made from a single material and may be pierced solely for the purpose of mounting and sealing, which must be carried out between the mounting screws, between the restrictor (or the restrictor/compressor housing attachment), the compressor housing (or the housing/flange attachment) and the turbine housing (or the housing/flange attachment) (see drawing 254-4).

In case of an engine with two parallel compressors, each compressor must be limited to a maximum intake diameter of 22.6 mm.

For vehicles with Diesel engines, the restrictor must have a maximum internal diameter of 35 mm and an external diameter of 41 mm, in the conditions set out above (this diameter may be revised at any moment without notice).

This restrictor, which is compulsory in rallies and in the European Hill-Climb Championship, is not prohibited in other events, should a competitor decide to use it.

6.2 - Transmission

- Clutch: The disc is free, including the weight, with the exception of the number and diameter.

6.3 - Suspension

The reinforcing of the suspension and its anchorage points by the addition of material is allowed.

- Springs: The spring seats may be adjustable if the adjustable structural part is a part of the spring seat and is separated from the original suspension parts/bodywork (it may be removed).

Coil springs: The length is free, as is the number of coils, the wire diameter, the type of spring (progressive or not), the external diameter and the form of the spring seats.

Leaf springs: The length, width, thickness and vertical curvature are free.

Torsion bars: The diameter is free.

These freedoms on the suspension springs do not authorise one to disregard article 205 of the homologation form (minimum height of the centre of the hubcap, wheel passage opening).

- Shock absorbers: Free, provided that their number, their type (telescopic, arm, etc.), their working principle (hydraulic, friction, mixed, etc.), and their attachment points remain unchanged. The damper tanks may be attached onto the unmodified shell of the cars. A silent block may be replaced by a "Uniball" joint, but only on condition that the shock absorber has no guiding function.

Gas filled dampers, regarding their working principle, will be considered as hydraulic dampers.

If, in order to change the damping element of a Mac Pherson suspension, or a suspension operating in an identical manner, it is necessary to replace the entire Mac Pherson strut, the replacement parts must be mechanically equivalent to the original ones and have the same mounting points.

For McPherson suspensions, the shape of the spring seats is free.

Their material is free.

In the case of oil-pneumatic suspension, the spheres may be changed as regards their dimension, shape and material, but not their number. A tap, adjustable from outside of the car, may be fitted on the spheres.

6.4 - Wheels and tyres

The wheels are free, respecting the homologated diameter (article 801.a), and the homologated width (article 801.b) which is considered as a maximum.

They must be covered by the wings (same checking system as in Group A, article 255.5.4), and the maximum track given on the homologation form must be respected.

Tyres are free provided that they can be mounted on those wheels.

The spare wheel may be brought inside the driving compartment, on condition that it is firmly secured there and that it is not installed in the space reserved for the occupants.

Wheels fixations by bolts may be changed to fixations by pins and nuts provided that the number of attachment points and the diameter of the threaded parts as indicated on drawing 254-1 are respected.

Air extractors added on the wheels are forbidden.

6.5 - Braking system

Brake linings are free, as well as their mountings (riveted, bonded, etc.) provided that the contact surface of the brakes is not increased.

Protection plates may be removed or bent.

In the case of a car fitted with servo-assisted brakes, this device may be disconnected. The same applies for anti-lock braking systems.

In this latter case, the fitting of a homologated mechanical braking distributor is authorised.

Brake lines may be changed for aviation type lines.

A device for scraping away the mud which collects on the brake discs may be added.

6.6 - Bodywork

6.6.1) Exterior:

Hubcaps must be removed.

Protective headlight covers may be fitted provided that their only function is to cover the glass, and that they have no influence on the cars aerodynamics.

The fitting of underbody protections is authorised in rallies only, provided that these really are protections which respect the ground clearance, which are removable and which are designed exclusively and specifically in order to protect the following parts: engine, radiator, suspension, gearbox, tank, transmission, steering, exhaust, extinguisher bottles.

Any locking system may be used for the cap of the petrol tank.

The fitting of external rear view mirrors is authorised, as is the changing of the windscreen wiper blades both front and rear.

6.6.2) Passenger space:

All accessories which have no effect on the vehicles behaviour are allowed without restrictions, such as those concerning the aesthetics or interior comfort (lighting, heating, radio, etc.), on the express condition that they do not influence, even in a secondary manner, the efficiency of the engine, steering, strength, transmission, braking, or road-holding.

Inversion of the driving side is possible, on condition that the original car and the modified car are mechanically equivalent and that the parts used are foreseen by the manufacturer for such a conversion for the family concerned.

The carpeting must remain in place.

All the controls must be those provided by the manufacturer and they must retain their original function but they can be worked on to make them more accessible or more easily usable ; for example, the addition of an extension to the handbrake lever, of an additional flange to the brake pedal, etc.

The following is allowed in particular:

1) Additional measuring instruments, counters, etc. may be freely installed, provided that their fitting is not likely to create any danger.

2) The horn may be changed. Another one, possibly for the passengers use, may be added.

3) The mechanism of the handbrake lever may be adapted in order to obtain instant unlocking (fly-off handbrake).

4) Seat-covers, including those creating bucket seats, may be added to the original seats, respecting art. 253.16.

5) Additional compartments may be added to the glove compartment as well as additional pockets to the doors.

6) The steering wheel is free. The locking system of the anti-theft steering lock may be rendered inoperative.

7) It is authorised to replace the electric window winders with manually-operated winders, using corresponding parts which are available for the model concerned. Likewise, the inner door panel may be replaced.

6.6.3) Reinforcements:

Reinforcement bars may be fitted on the suspension mounting points to the bodyshell or chassis of the same axle, on each side of the cars longitudinal axis, on condition that they are removable and are attached by means of bolts. The distance between a suspension attachment point and an anchorage point of the bar cannot be more than 100 mm, unless the bar is a transversal strut homologated with the rollbar, or unless it is an upper bar attached to a MacPherson suspension or similar. In the latter case, the maximum distance between an anchorage point of the bar and the upper articulation point will be 150 mm (drawings 255-4 and 255-2).

Apart from these points, this bar must not be mounted on the bodyshell or the mechanical parts.

Strengthening of the suspended part is allowed provided that the material used follows the original shape and is in contact with it.

6.6.4) When the spare wheel is originally set in a closed accommodation, and when this wheel is changed for a thicker one (see article 6.4), situated in this space, it is possible to remove from the cover of the location of the wheel the surface induced by the diameter of the new wheel (drawing 254-2).

6.7 - Electrical system

- Battery: The make, capacity, and battery cables are free. The tension and the site of the battery must be retained.

- Generator: May be replaced by a more powerful one. A dynamo may not be replaced by an alternator and vice-versa.

- Lighting system: Additional headlights including the corresponding relays are allowed, provided that the total does not exceed eight (tail and parking lights not included) and that this is accepted by the laws of the country.

They may not be housed within the bodywork. Headlights and other exterior lights must always exist in pairs.

The original headlights can be made inoperative and covered with adhesive tape. They can be replaced by other headlights, in compliance with this article. A reversing light may be fitted provided it can only be used when the gear lever is in the "reverse" position, and provided that the police regulations on this subject are observed.

- Fuses may be added to the electrical system.

6.8 - Fuel circuit

Providing the original tank is equipped with an electric pump and an interior filter, it is possible when using an FT3 or FT3 1999 tank or another tank homologated by the manufacturer on the cars homologation form to place a filter and a pump with identical characteristics to the homologated one outside. These parts must be protected in adequate fashion.

The fitting of a second fuel pump is authorised, but this must be only a spare fuel pump, i.e. it cannot operate in addition to the authorised pump. It must be connectable only when the car is immobile and by means of a purely mechanical device situated beside the pumps.

The filler holes may not be located in the window panels.

Fuel lines must be changed for aviation type lines if an FT3 or FT3 1999 tank is used, the route of these lines being free. Should a series production tank be used, this change is optional.

The total capacity of the tanks must not exceed that indicated in article 401.d of the Group N homologation form, except for rallies, if the car is fitted with FT3 or FT3 1999 tanks. In this case, the total capacity of the tanks must not exceed the following limits, in relation to the engine capacity:

Up to
700 cm3:
60 l

700 cm3
1000 cm3:
70 l

1000 cm3
1400 cm3:
80 l

1400 cm3
1600 cm3:
90 l

1600 cm3
2000 cm3:
100 l

2000 cm3
2500 cm3:
110 l

2500 cm3:
120 l

For cars homologated from 01.01.98, with a fuel tank installed in the luggage compartment, a fire-proof and liquid-proof case must surround the fuel tank and its filler holes.

6.9 - Jack

The jacking points may be strengthened, moved and increased in number. These modifications are limited exclusively to the jacking points.

What it basically states in the first sentance is a bit mis-leading. 2500 identical cars must be made for at least a year, then it goes onto state you can more or less modify most of it beyond recognition!
  Clio 197

Lokks like they relaxed the ruling. I think it used to be 5000 cars, and 500 for an evolution.

No, you dumbass ;) Though it would be great for the new version, depends on the regular ones success i guess. Id call it the V6 Trophy though. :)

You cant modify beyond recognition a car entered for Grp N compettion has to be basically showroom production model with added bits which are strictly regulated and controlled so you cant exceed the regs or power output of the car etc.