It is rare, very rare, that the automotive media checks “real” car performance, consumption or even stopping distances. For more than thirty years, L’Automobile Magazine has been part of this closed club, which in France has two other members in the specialized automotive press.. At a time when some are not bothered about ethics, we wanted to highlight our way of working in complete transparency and explain to you how and why we measure cars on the Montlhéry circuit. Fasten your belt.
More than 200 cars measured per year: what else?
Over thirty years ago, the editors at L’Automobile Magazine decided to measure the test cars with their own funds. The aim is to check, to help you, the promises made by the manufacturers on the figures of their cars. Because this approach can only be rigorous if accompanied by precise protocols and dedicated equipment, AM has invested quite a bit. Flowmeters to measure fuel consumption to the nearest milliliter, brake graph, radar or, more recently, two special counters to check electricity consumption and the time spent during recharging, in total, more than €100,000 worth of equipment is used to support our tests. The latter, always made in the same way, thus makes it possible to compare the cars with each other in a fair way.
Private tracks to avoid disturbing elements
Indeed, what honor can we give to measurements taken in full circulation with all the dangers involved and without any means of verification? A bit serious! In fact, it is for this reason that L’AM has decided to take you to an open day on the most secret French tracks.. We work at the Autodrome de Montlhéry, located 30 km south of Paris. And know that you are privileged because access to this site belonging to UTAC – the organization that certifies, from tractors to cars via buses, vehicles circulating in France and Europe – is mostly forbidden to the prying eyes of the curious.
If you trust the trip computer to calculate your consumption, be aware that it is often very optimistic. Since 2020, a new regulation has definitely required a margin of error of 5% at most, but it’s still hard to tell if his car is greedy depending on the traffic conditions. Apart from doing the calculation yourself by dividing the number of liters put back in the tank when refueling by the number of kilometers driven.
On our side we use a flow meter. Connected directly to the vehicle’s fuel circuit, this device records, to the nearest cm3, the consumption of the tested car. All that remains is to simulate the driving conditions on the tracks of the Montlhéry circuit. For each of our three bikes (city, road and highway) we have set a single route that reproduces reality as much as possible: stops/restarts at traffic lights or stop signs on the city bike or even multiple overruns on the bike highway because we never travel 100% of the time with the control speed.
All, absolutely all cars are therefore measured in the same way, which means that they can be compared with each other. It is clear that you can consume less or more with your own car. The way you drive, where you live (city or mountain, etc.) or the condition of your vehicle (poorly inflated tires, wear, etc.) can affect the appetite for mechanics.
Electricity consumption and autonomy
Measuring the consumption of an electric car is not an easy task. Again, the on-board computer can be an indicator, but don’t rely on it blindly. In fact, if the remaining autonomy recalculated permanently is quite reasonable, it is far from the case of kWh / 100 km. The explanation is that an electric car also consumes energy when it is plugged into a socket when it is being charged.. The built-in charger is actually energy intensive, as is the battery cooling system, which continues to operate under load. However, these kWh are not displayed on the dashboard, but you pay for them!
In fact, we use two meters, calibrated and verified by UTAC, to measure the amount of energy consumed and the charging time of our WallBox, which delivers an output of 7.4 kW. And then we proceed almost in the same way as for the thermal models by checking, at each end of the cycle (city, road, highway), the amount of energy needed to recharge the battery to 100%. To increase autonomy, we also simulate travel by driving for a long, very long time on the slopes. To be as accurate as possible, we drive with the heating or air conditioning switched off (summer and winter) and windows closed. In fact, you will not find all the figures that we advertise according to your region and your routes, but we can therefore indisputably classify the cars between them.
Finally, you should also know that we do not measure the range or consumption of plug-in hybrid or 100% electric cars when the temperature drops below 15C°. A low thermometer has a negative effect on the batteries. It would therefore be unfair to reject models measured in the cold season.
Read also: what differences in autonomy between summer and winter in a rechargeable hybrid?
Performance, braking and noise
For the performance of the cars, in other words the accelerations and the pick-ups, we use a radar. Even more than 0 to 100 km/h, 400 or 1000 m start-stop, the most useful data are the times, in other words, a car’s ability to drive from 80 to 120 km/h. The shorter the time, the safer the overhaul. For models with a manual gearbox, the exercise is repeated on the last three gears. Note that we do not measure top speeds for two reasons. The first is that this data is of little use in a country where the rules allow a maximum of 130 km/h on the motorway. The second is due to the rules, as it is forbidden to exceed 200 km/h on the speed ring of the Montlhéry track.
As with the other measures, braking distances are measured using a device, in this case a brake graph. The latter makes it possible to record the distances, the stopping time and the deceleration in seconds of the tested model. This device also makes it possible to ensure the quality of the operation of the ABS. Finally, far from being trivial, noise is also important in a car. In fact, with the help of a sound level meter, we record the number of decibels on board at idle, at 90, 110 and 130 km/h.
Habitability and weight
Large exterior does not necessarily mean spacious inside. In fact, our measure of livability is used to know which model gives the most to its competitors. We first try to measure the space offered to the passengers. At the front, we always place the driver’s seat in the same way. From there we are able to compare legroom, headroom or even shoulder width.
For the volume of the trunk, we have a set of suitcases. In this respect, our numbers are very far from the manufacturers. Logical, because for approval the latter uses water or plastic balls. This method provides the maximum volume available, but it takes into account the smallest corner, which you will then never be able to exploit under your loads.
Finally, because between the empty weight, the weight with the DIN standard (without the driver but with 90% full) and another EG (68 kg driver + 7 kg luggage) we end up getting lost, we take the weight of the test cars on an approved scale. The latter allows us, in passing, to know the distribution of the mass between the front and the rear and to note that there, too, manufacturers are often optimistic…
More than 300 measures to serve you
Heavy investment both from a human point of view with Bruno Servant, our measurement manager, who is in Montlhéry every day of the week, and on the equipment side with the rental of the box, access to the slopes and purchase/maintenance of the devices, our measurements are of crucial importance. Not only do they ensure the independence of the oldest title in the French automotive press from the manufacturers, but they also allow you to check the qualities and defects of a car for you.. So now no more excuses when you are told about “goals” or “real numbers”.