Definitions: Homologation

In some of our past and upcoming articles, we’ve been throwing around the word homologation, and it occurs that we should pause to explain what it means.


Most types of motor racing have complex rules and regulations designed to pit like against like. Competitors are typically divided into classes based on factors like engine displacement, power-to-weight ratio, wheelbase, or list price, so that (for example) a 1,000 cc (61 cu. in.) supermini is running against other 1,000 cc mini-cars, not against 5-liter (305 cu. in.) V-8 sports cars.

Sportsmanship and the spirit of honest competition notwithstanding, such rules are very much driven by money. Motorsport is big business, which gives race promoters and officials a strong incentive to maintain a relatively equal playing field — they want to ensure that audiences get a good show. At that time, however, the publicity value of racing victories and championships gives manufacturers and teams a strong incentive to win even if that means taking what we might politely call creative liberties with the rules.


One of the ongoing dilemmas for the various racing officiating bodies is trying to curb manufacturers’ natural temptation to stack the deck with purpose-built engines and other experimental hardware. Of course, some forms of motor racing do have prototype or factory experimental classes, but, at least to our point of view, pitting a one-off engineering special against modified stock cars is more an academic exercise than an exciting race.

A common regulatory tactic to require that race cars be based on a production car. However, especially for smaller manufacturers, the exact definition of “production car” can be hazy indeed, which requires racing officials to set specific rules and minimum standards.

To that end, most (though not all) forms of professional motorsport turn to racing’s international regulating body, the Fédération International de L’Automobile (FIA). The FIA addresses the production question by dividing race cars into a series of groups.

A group is not the same as a class, and there are typically several classes within any group. Rather, each group is a set of rules specifying how many production copies, if any, the manufacturer must build before a car may compete and how closely the competition cars must match the specifications of their production counterparts. (Racing series that don’t follow FIA rules develop their own standards for the same purpose.)


Before a given car is allowed to race in any official event following a specific set of group rules, the manufacturer must first submit detailed specifications of the production car to the appropriate regulating body, along with the manufacturer’s assertion that the requisite number of production cars have been offered for public sale.

This process is called homologation — derived from the Greek homologeo, meaning “to agree” — because the specifications of the competition car must follow those of the production model within the range of variation permitted by the rules. For instance, a given set of rules might require the race car to use the same engine block and cylinder heads as the production car while allowing changes to the valves, camshaft, and manifolds. (FIA group rules are much more extensive than just that, but you get the idea.)

Homologation is a prerequisite for qualification, not a substitute for it. A specific car might be properly homologated and still be disqualified for a given race for having non-homologated components or prohibited modifications.


In certain cases, engines and other components can be homologated separately from the cars themselves. For example, if a manufacturer produces 500 examples of a particular engine and 500 examples of a particular car, race officials might permit the car to be raced with that engine even if that specific combination hasn’t been offered to the public.

Sometimes, a regulatory body will also allow manufacturers to field cars with incremental changes or variations from the original homologation specs. Such “evolution” models usually also have to be homologated, but the requirements are generally lower. For example, the manufacturer might only need to build 250 cars to the new spec even if the original requirement was 5,000 units.


Homologation rules don’t prevent manufacturers from developing purpose-built racing versions of their cars; the rules simply make it more expensive. There have been many examples over the years of features or models offered to the public in limited numbers for the sole purpose of facilitating racing homologation.

Such “homologation specials” are usually rare, expensive, and not necessarily well-suited to normal driving, but they do have a tendency to become coveted collector’s items. Famous examples include the Dodge Charger Daytona and its Plymouth Road Runner Superbird cousin; the fearsome Porsche 959; and the original BMW E30 M3.

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  1. Homologation seems to be the best way to ensure racing efforts follow through on their promise that racing developments can help make better street cars.

    In the best cases, tweaks are made to the design of the base car to help the race version: things like engine configurations or chassis design.

    The US would do well to trade NASCAR for series’ more like BTCC or DTM.

    1. [quote]In the best cases, tweaks are made to the design of the base car to help the race version: things like engine configurations or chassis design.[/quote]

      Well, sometimes. Historically, that’s really been hit and miss. Look at the Group B cars of the mid-80s — Porsche applied a lot of the 959’s technology down the line, but for a lot of the manufacturers involved, it seems like they just dropped it and had to reinvent it later. There are some cases where racing technology has filtered down (I think modern AWD is a key example), but also a lot where one hand just didn’t talk to the other.

      I think NASCAR has become far less interesting since their cars stopped having any resemblance to stockers in the early 70s. At the time, it was a reflection of political realities — the automakers could no longer get away with offering side oilers and Hemis for public sale, and they needed to turn their resources toward emissions controls and safety standards — but it rendered NASCAR largely irrelevant from a technological standpoint. On the other hand, a lot of the improvements developed for NASCAR and Trans Am (particularly the aerodynamic addenda) never really went anywhere, anyway, so maybe it doesn’t matter that much.

  2. I guess that’s the point I’m getting at.

    I see the whole point of homologation rules as encouraging/forcing race teams to pursue solutions that might benefit road going cars in some way.

    I’d love to see a GT-esque series that had a fixed fuel quantity for any given race. It’d be just enough to get it done if you’re clever, but would force teams to think about fuel consumption.

    Maybe allow active aero features, too. Wouldn’t it be cool to see cars get all slippery in the straights, then puff up like a pufferfish going into a corner?

    1. [quote]I see the whole point of homologation rules as encouraging/forcing race teams to pursue solutions that might benefit road going cars in some way.[/quote]

      Well, that can be a benefit of it. I think the principal rationale is to try to keep deep-pocketed manufacturers from dominating series with cost-no-object one-offs. I think the fixed-fuel series would be a good exercise, though.

      Active aero has been controversial for 40 years. Do you know/remember the Chaparral? Active downforce — basically sucked itself to the track. Amazing thing, but started enormous controversy.

      My understanding is that the prohibitions against active aero have to do with trying to keep maximum speeds out of the stratosphere, on the principle that 300-mph F1 cars are bad for safety.

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