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Stock, Stage 1,2,3 and 4, what is it?

We often use the terms Stock and Stage 1,2,3,4, terms that many people do not necessarily understand, especially if they are not in the sphere of performance cars.

It is in fact designation on the level of the reprogramming of the engine. It is a manipulation which allows to boost and increase the power of the engine.


We say that a car is Stock when it has not undergone any modification to the engine and its mapping. It is as it left the factory.

We speak of Stage when the engine and / or its mapping has received modifications. There are 4 Stage levels ranging from 1 to 4.

- Stage 1 Engine reprogramming:

It does not affect the mechanical part, but only everything that is electrical and connected to the electronic box of the car. The vehicles are manufactured in accordance with certain standards but also by responding to different respective constraints in different countries. It is for this reason that the engines are restricted by an electronic engine control unit (ECU: Engine Control Unit). The ECU controls the engine parameters.

In order to gain power and torque and take full advantage of the vehicle's performance, a reprogramming of the engine mapping by modifying the ECU is used.

Reprogramming is done on engines fitted with a turbo, because the gain is significant unlike naturally aspirated engines which have a low gain.

The operation generally gives an increase in power of around 10 to 30% of the vehicle and is accompanied by a reduction in consumption and pollution because the engine is less stressed during acceleration phases. While the operation may seem attractive, it is not without risk.

Engine reprogramming is tailor-made depending on the type and make of the car. This manipulation takes place on a power bench which is equipped with 4 rollers so that all vehicles are accepted (whether they are 2 or 4 wheel drive). It must be carried out by specialists capable of correctly modifying, via software, the curves of the manufacturer's mapping.

The first step consists in passing the vehicle on the dyno in order to determine all the characteristics of the engine thanks to a high-tech equipment making it possible to extract the data and the original mapping from the computer such as power, performance, engine operating cycles. The original file can be extracted either via a diagnostic (OBD) or following direct intervention on the computer.

Between two models of the same vehicle, the performance obtained may thus vary.

In short, engine reprogramming consists of manipulating and modifying the internal data of the engine ECU.

- Stage 2 Engine preparation:

This course unlike the first is also accessible to slightly modified vehicles. This is a more advanced version than Stage 1.

Here is what is done during an engine preparation stage 2:

Reprogramming the computer.

Switching from a manufacturer's air filter to a sports air filter.

The exhaust line after the catalyst

Attention on a diesel engine this course consists of stripping the vehicle

Here are the accepted modifications to carry out an internship 2:

sport air filter,

cata or fap deletion,

EGR valve removal,

exhaust line,


air exchanger…

Stage 3 Engine preparation:

This internship is an improvement of stage 2 since it incorporates what we saw in stage 2 but the evolutions are more important:

Reprogramming the computer,

Switching from a manufacturer's air filter to a sports air filter,

The exhaust line after the catalyst ...

Attention on a diesel engine this stage consists in stripping the vehicle. Modification of your air exchanger, if necessary the original injectors will be changed for high flow rates. Change from an original clutch to a reinforced clutch.

Stage 4 Engine preparation:

This course is a no limit course !! and the changes are under the sway of the reprogramming wizards.

Vehicles after intervention by the seller as part of a modification of the engine mapping no longer comply with the original certificate of conformity and can no longer normally circulate on public roads. The operation thus involves risks, both in terms of your civil liability as well as that of your insurance coverage.

Is engine reprogramming at the expense of reliability?

This statement is both true and false.

TRUE. Reprogramming is not a trivial operation, since it affects the engine speed, ignition and injection advances or turbo pressure, parameters that can lead to destructive mechanical and thermal stresses.

FALSE. Manufacturers equip several vehicle models with the same engine base, but operated with different maps (the same engine will have its own power depending on the configuration chosen: 90, 110 or 130 hp). It is therefore possible to modify the performance of an engine, provided that:

this reprogramming is carried out by a competent company and operator;

the increase in performance remains within the framework defined by the manufacturer and that the engine environment is taken into account (different radiator or cooling temperature regulator, for example);

an assessment of the condition of the engine is carried out before reprogramming.

What happens on resale?

Knowing that the return to the original settings of the computer is done in a few minutes at your preparer, many sellers bring their vehicles back before resale.

According to preparers, many sellers are reverting to the original power to avoid scaring the future buyer about reliability, insurance, etc.

As the vehicle is no longer in phase with its homologation and its initial conformity, your buyer not informed of the operation and victim for example of an engine failure, will be entitled to request the cancellation of the sale. The courts hold in such circumstances the presence of a lack of conformity. In addition, during the sale of the vehicle, if you did not therefore mention the existence of significant transformation on the transfer certificate (space dedicated to this purpose), you are committing a forgery and use of forgery.

What happens with the additional boxes?

Additional units allow entry-level engine reprogramming that many car tuners advise against, in fact, this type of unit will send erroneous information to the computer so that it increases certain parameters in order to increase power.

The price is unbeatable, however, they are detectable because by deceiving the computer, it can exceed manufacturers' standards, which can be dangerous for the engine.

Indeed, it is a cascade phenomenon that will trick the brain of the car. While the engine reprogramming goes directly to the heart of the computer with all the parameters available while being able to remain more easily within the manufacturer's standards because the control takes place over the entire engine control chain.

In addition, in the event of an accident, if you cannot access the vehicle to remove the tuning box, in this case, the expert will quickly see that a modification has taken place!


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