TEST: HOW IT DOES
DO NOT MEASURE ARSHIN TOTAL?
ALEXEY SPARROW-SHOES, ANATOLY KARPENKOV. PHOTO: ANATOLY FOMIN
Only independent tests, primarily automobile magazines, allow objective comparison of competing cars.
Often, letters like these come to the editorial office: “So you write that the car X picks up a hundred in 10 seconds and accelerates to 172 km / h. And I measured …”Further options with worse (more often) or better (less) indicators are possible. Why do not the results obtained by manufacturers, journalists and car owners match?
SECONDS MEASURED BY DEGREES
The maximum speed and speed of dialing the first hundred are the parameters that almost every owner of a prestigious brand boasts among his friends. To confirm their words, some even arrange nightly high-speed rides on the Moscow Ring Road in the … area of DPS video cameras. Just to document the impressive numbers! Well, traffic cop radars are fairly accurate instruments, but the measurement conditions are different … And yet - how objective are the manufacturers data that fall into the brochures?
Manufacturers for their purposes are ready to please the vanity of future buyers and sometimes go to one or another trick if they do not contradict the regulatory documentation. Let’s say they pour special low-viscosity oils into engines and transmission, put lightweight rims with special tires, cover plastic seats that are bad for aerodynamics on the bottom and in the wings.
But the most important thing is that not everyone follows a uniform standard in such measurements. As a rule, they choose a model with a minimum configuration (that is, the lightest), with a feeble driver and some additional cargo in the cabin. At FIAT it is equal to 30 kg, at Volkswagen - 200 kg, Peugeot puts half of the permissible load. These are not trifles: the extra 100 kg can add a whole second!
How to compare the real dynamic capabilities of cars of different manufacturers, and even from different continents? For this, we need tests of automobile magazines: each of them measures the treasured seconds by a single method, regardless of the brand of the car and its origin. Everything would be fine, but the measurement conditions do not coincide with the factory ones. A living example is FIAT-Punto 1.4. The Italians indicated in prospectuses 9.9 s to hundreds provided: curb weight 960 kg, driver and 30 kg of ballast. And the journalists of the Swiss Automotive Review (they publish the famous Geneva catalogs) received a car with options that pulled 1050 kg. Yes, they put a passenger and rode at an altitude of 500 m above sea level at + 24 ° C. Result: 11.6 s to hundreds.
Taking into account atmospheric pressure and air temperature “shortens” the acceleration to 10.9 s, another second leaves if you unload an extra rider, and take the mass of the car equal to the factory one. In the end, the Swiss made a decision: to publish the results only after the conditions are reduced according to special formulas to the standard ones: 20 ° C, 1013 mbar, the actually measured weight of the sample submitted for the test with a full tank and a load of 150 kg, including the driver.
Everything? Not at all. It is necessary to test run-in cars! So, Volkswagen starts factory tests if the mileage is at least 3, 000 km for gasoline engines and 5, 000 km for diesel engines and off-road vehicles. An experiment conducted with KIA Sorento, for example, showed that a car after 3700 km accelerates to a hundred in 14.6 s, and after 50 000 km this figure drops to 13.8 s!
We have established equal rules for all participants in our tests. The basis was taken by the permanent Russian GOST 22576. Therefore, the experimental cars go out onto the dynamometer road of the NITSIAMT training ground in Dmitrov with a fully filled tank and a load of at least 180 kg, including the weight of the driver, instrumentation and measuring equipment. Hot? We'll have to tolerate: the windows and hatches must be closed, the top of the convertible is raised. And the air conditioner must not be turned on, as, indeed, the heater, ventilation, radio … Another thing is the dipped beam, it is obliged to ignite safety rules.
Before the test race, as it should be, a warm-up: the car must drive at least 50 km at a speed of 2/3 of the maximum speed. Thus establish the thermal regime of units and tires. By the way, if the street is less than + 3 ° C, or humidity is higher than 95%, or the wind is stronger than 3 m / s - you can’t measure the dynamics. Therefore, all tests of this kind are carried out only in the warm season. In winter, they conduct special comparative tests, for example, tire tests, and during them they also measure the dynamics of acceleration, but these are not the limiting characteristics of the car itself.
Why choose a landfill? Its dynamometer road corresponds strictly to GOST: the longitudinal slope is not more than 0.5%, the transverse - 0.3%, the length of the working section is not less than 2000 m (actually there is even 5000 m). And, of course, it’s simply safer to ride in a closed, specially planned area!
So, all the requirements are met, the machine is weighed, the equipment is on - go! For data objectivity, we sweep across the measured area three times back and forth. And God forbid that the intended results do not differ from each other by more than 3%. Otherwise, you have to look for the reason and start all over again.
DO NOT REPEAT - DANGER!
Of course, everyone will be able to start with a squeal from a traffic light. But is he good at being testers? Perhaps, we’ll have to upset most drivers - the official test run is quite different from the banal street showdowns of “who is cooler”. A driver who is entrusted with receiving figures that subsequently rejoice or depress eminent companies must have special skills and qualifications. And this directly depends on the experience and regularity of training.
For example, when driving in a car with “mechanics”, it is necessary to juggle the lever for 0.1–0.15 s without gas discharge, as soon as the engine speed rises to the corresponding maximum power. Acceleration is most advantageous with a small slipping of the drive wheels - this results in minimal seconds. At the same time, one must also think about not ditching the often very expensive sample provided for the test by the press garage of the manufacturer or seller.
With the "automatic", of course, easier: gas to the floor and drove. But here it is also necessary to make a “shutter speed” on the brakes before a jerk and not to allow significant slippage. Nevertheless, the testers turn off the electronic traction control (if any) - it “strangles” the motor, so you won’t get full numbers. But the “sport” box mode is just for such races.
Suppose, however, you despised the risk and, arming the volunteer assistant with a stopwatch, you decided to double-check the numbers given by the factory or in the magazine on your own car. In vain spend time and resource of the machine. After all, a second can be mistaken for a couple of tenths, and a regular speedometer will lie - it will take inexpensively.
We will not touch our races without special, verified equipment. The modern and very expensive Korsis complex painstakingly records the entire acceleration curve on a special memory card so that later, in peace and quiet, you can play the race on a computer screen. This is very convenient: you can evaluate acceleration not only to hundreds, but also to 40, 60, 80 km / h - as you like! Another thing is bad: the optical speed sensor is of a fairly decent size and … it introduces additional aerodynamic drag. However, we have long determined the value of this error and introduce a correction for it (up to 2.8% depending on the location of the sensor on a particular car).
NO RULES WITHOUT EXCEPTIONS
Sometimes we are in our own interests or forced to nevertheless depart from the formal lines of GOST. Well, for example, we start to measure the coast at 120 km / h, and not at 50 km / h. In this case, the first half of the curve allows you to further evaluate the aerodynamics of the car.
Another problem is the requirement of the document: the “experimental rabbit” must run at least 3000 km before the tests, that is, it must be run-in. It is clear - friction pairs must be run in. But not all firms and car factories have exactly such machines in their press garages (sometimes they don’t even have such garages).