homologation insights (KARTING)
Founded in 1904, the Fédération Internationale de l’Automobile (FIA) has a mandate to govern all classes of competitive motor sport worldwide, and at present there are 144 countries that are affiliated to the FIA. There are many different categories of motorsport and hence the FIA has appointed various commissions to assist in the control of them. Created in 1962, the Commission Internationale de Karting International (CIK-FIA, and also simply referred to as the CIK) is the entity responsible for the subsection of vehicles called karts. Some of its main missions are to ensure unity within karting, to promote and develop karting throughout the world, to develop sporting and technical regulations, and to establish the international competition calendar.
It would however be impossible for them to be hands-on in all the 144 countries that are affiliated to them, and hence they are assisted in each country by the appointed National Sporting Authority (ASN) holding the sporting power in accordance with its FIA membership. In the case of South Africa, this entity is Motorsport South Africa (MSA) which is the organisation officially recognised by the Department of Sports and Recreation.
Karting championships
For 2-stoke karting as we know it, at the pinnacle of the sport there are two international championships viz. the Karting World Championship, and the Rotax Max Challenge. Essentially both championships adhere to the generalised technical and sporting prescriptions laid down in the CIK rules, but the Rotax Max Challenge employs the use of a one make engine manufactured by BRP-Rotax in Austria. For this reason the engines must comply with the Global Rotax Max Challenge Technical Regulations, which is the same as those used here in South Africa.
Kart groups
The CIK has always chosen to govern categories for competitors (drivers) who are old enough to obtain an international licence (currently the minimum required age is 13 years old), and the management of any classes below this age is left up to the ASN’s. The CIK categories are divided into families viz. gearbox karts, direct drive karts, and super karts. All these karts make use of the 2-stroke engine, and although it has not yet introduced them into its own range of categories, the CIK nonetheless keeps a close eye on the developments in other technologies such as 4-stroke or electric powered karts for possible inclusion in the years to come.
Direct drive karts (chain driven) have always been in the majority and from the inception of karting, the 100cc karts were the most popular in use. They prevailed for almost 50 years before the change to the current capacity which is 125cc. In order to differentiate between the various types of karts that currently fall under their control, the CIK have categorized 2-stoke karting into a number of groups that are essentially based on engine size. Groups 1 and 2 make use of the 105cm wheelbase chassis, whilst Group 3 karts (also known as Mini’s) use a slightly smaller 95cm chassis.
Group 1 125cc engine with gearbox
Group 2 125cc engine with direct drive
Group 3 60cc engine with direct drive
Group 4 250cc engine with gearbox.
For Group 1 karts, the minimum weight is around 170kg which includes the kart and driver. They can accelerate from 0 - 100km/h in 3,5 seconds and can reach a top speed of 180km/h. Group 4 viz. Super karts are powered by 250cc twin-cylinder engines developing nearly 75kW, but being just over 200kg including the driver, are phenomenally quick to the point where their lap-times on circuits such as Silverstone or the Nürburgring will put many exotic cars and single-seaters to shame. Bodywork-wise they are akin to F1 cars with enclosed bodies and the driver is almost in a lying position.
Kart classes
Because of the foregoing, the classes of karts competing in the World Championship are different to those in the Rotax Max Challenge. In the former, the more junior of the classes that fall into Group 3 viz. Kid Rok and Mini Rok are not catered for and the classes that currently compete in Group 2 are OK Junior, OK Senior (simply called OK), whilst for the gearbox karts in Group 1 it is KZ1 and KZ2. The competing classes in the Rotax Max Challenge are Micro Max, Mini Max, Junior Max, Senior Max, and the gearbox driven DD2. All of the Rotax classes now make use of same basic 125cc engine with increasing power being derived from the deletion of inlet/exhaust restrictors, freer flow exhaust systems, different squishes, and the incorporation of a power valve for the Senior Max and DD2 classes.
The 125cc engine
The 125cc engine came into being as a result of a number of factors. In order to extract more power, the 100cc engine in use at the time had been developed to such an extent that the engine revs in some instances exceeded 20,000 rpm and this made them both fragile and extremely costly to maintain. Because of the high pitched exhaust sound generated, they were also fondly referred to as the ‘screamers’. To give you some idea of what those sort of revs translate to within the engine, it meant that the mean piston speed was in excess of 33m/s whilst todays F1 engine at 15,000rpm has a piston speed of 26,5m/s. Many of these 100cc engines also used a disc valve attached to the crankshaft which meant that the carb was mounted on the side of the motor, and the accompanying picture shows the inlet port on a typical engine of that era. Any new replacement engine destined for use in karting had to remain user-friendly, incorporate modern technology, whilst keeping exhaust emissions to a minimum.
One of the easiest solutions might have been a switch over to 4-stroke technology but this would have brought with it a number of technical problems. A 4-stroke engine develops roughly half of the power of a similar capacity 2-stroke, weighs a lot more, and is a much more complex design incorporating a camshaft, push rods, rocker arms, and both inlet and exhaust valves located in the cylinder head. Consequently after much consultation with all the stakeholders it was decided to develop a 125cc 2-stroke engine that incorporated many new technologies such as a reed valve inlet system, electronic ignition, a rev limiter, etc., and this was introduced in the early 2000’s.
Because of their increased capacity these engines include a balancing shaft to reduce inherent vibrations particularly at higher operating revs. In some cases an integrated water pump is fitted for those versions that are water cooled. Some models incorporate an electric starter and a centrifugal clutch, or alternatively a decompression valve and no clutch to allow the kart to be push-started. All have an ignition system which includes a rev limiter, and on the more senior and faster classes an exhaust valve, also called power valve, is fitted. Those with gearboxes also have very specific gear ratios that, depending on the series, need to comply with either the CIK or Rotax regulations.
HOMOLOGATION
In order to keep the playing field level, the CIK specifies that many of the components used on a kart need to be homologated. So the question arises - what is homologation? It is the official assessment made by the CIK that the item in question has been built in sufficient numbers and complies with the specifications laid out in the regulations governing the group in which it is to be used. Once the item is submitted for testing and been approved by the CIK, the homologation is usually only valid for 3-years but may be extended by them.
Homologated items can be identified by homologation number that must appear on the item. In order to qualify for homologation, the equipment must obviously have minimum production quantities available for sale, and as an example this would be 75 for a chassis, bodywork, brakes, 50 for an engine, carb and exhaust, and 500 for tyres. These are not the only items covered by homologation and for safety reasons there are also strict requirements laid down by the CIK for wearing apparel such as race suits, helmets, rib protectors and the like. All homologation certificates contain standard items such as the manufacturer’s name, model name, date of approval, validity period, photographs and sketches of the items, important dimensions, and in some instances tolerances are also provided on critical dimensions.
Abbreviations on a nameplate, or stampings on the components indicate the type of equipment that is homologated and are derived from their abbreviated French names as follows.
By way of example, to qualify as a chassis manufacturer, apart from having all the necessary QA/QC requirements to ensure consistency of the finished product, the manufacturer must have access to an adequate research department. In addition to the standard items, the homologation certificate for a chassis would list the diameter of the main tubes (anything longer than 150mm), quantity of bends, dimensions indicating wheelbase, fixing points for bodywork, and a photograph of the homologation plate that is attached to the chassis. All chassis used in the Rotax series are required to bear the CIK homologation marking but because of the rear axle mounting method used in the DD2 class, the applicable chassis have a Rotax homologation. Rotax homologation certificates usually don’t have a specific validity period. Similar QA/QC requirements apply to a brake manufacturer as well as other homologated equipment, and typical markings on a homologated chassis and also a brake system are shown below.
For tyres, the slick versions usually fall into two categories viz. an Option tyre, or a Prime tyre which provides a higher performance but reduced life. The manufacturer must provide self-certification stating that his tyre can cover 250km (Option tyre and also the Mini tyre) or 150km (Prime tyre) under all circumstances. Note that this don’t imply that one can still be competitive with the front runners if the tyres have been used for these distances. The CIK may also verify this classification by conducting track tests in accordance with their prescribed testing method for tyre classification via wear life. Track testing is then conducted in sessions for up to the distances mentioned previously, or the tyre wears out prematurely i.e. the cord material becomes visible.
As we are well aware, all tyres are not created equal and exhibit both different wear and handling properties. For comparison purposes, the table below provides some insight on selected tyre properties for some of those we may have used or are about to use.
The hardness is expressed in international rubber hardness degrees (IRHD) measured in accordance with the methods defined in the ISO 48 standard. Note that the recommended pressures are those provided by the tyre manufacturer and provide a good starting point for experimentation on your kart. All that said, the tyre one uses in a given class is not a choice that is left up to the Competitor as these are laid down in the class regulations.
Emile McGregor - MSA Technical Consultant