Contrary to what some people think, the fiscal horsepower of a vehicle is not a physical unit of power. They are simply a value that indicates how much you have to pay in the Spanish Mechanical Traction Vehicle Tax and many other countries.
The fiscal horses or CVF are indicated in the Vehicle ITV Card, in the Fiscal Power (CVF) section. Right after, the power expressed in kW is indicated, which is a unit of measurement used in physics and which does express the real power of the motor. However, this has no effect on the tax we pay.
What exactly are fiscal horses or fiscal power
The fiscal power or fiscal horses of a vehicle is a number that is obtained with the engine displacement. That is why values such as cylinder diameter, Piston race and number of cylinders. The more displacement, the more fiscal horses.
in the engines electrical and combustion rotary is obtained with its effective power. Another value, which also has nothing to do with the maximum power of the vehicle on which the calculation is made.
Convert tax horsepower to kW or hp
Actually, trying to get the real power of an engine from the tax horsepower it is absurd. As we have told you before, fiscal horses they are not a physical measure that indicates the real power of the car. Therefore, is not a supported value that can be changed from unit of measure. Hence, it makes no sense to ask: "How many fiscal horsepower is 110 CV?" There is simply no correlation.
As the fiscal power is related to the cylinder capacity of the car, only in the past could it have some correspondence with some naturally aspirated engines. Even so, an exact conversion could not be done, since there are many other factors that influence the real power of the car in addition to the displacement. For example, the number of revolutions per minute (rpm) that the motor can achieve or the compression ratio.
in the engines electrical o combustion rotary can't do this conversion either, because their fiscal horses are obtained with the effective power. A value that also has nothing to do with the maximum power of the car in CV or kW. Below we detail more about the fiscal horsepower of these types of engines.
What can be converted without problems are the kW to hp and vice versa. Simply multiply the kW by 1,36 and you will get the CV of your vehicle. Obviously, if you want to convert hp to kW, you just have to divide the hp by 1,36 and you will get the kW.
How to calculate the fiscal horsepower of any car
Method 1
Calculate the fiscal horses of any model It's very easy with this method.. Enough with use engine displacement instead of the values that we have mentioned before (piston stroke and cylinder diameter). Some data that are not so easy to know for everyone. The calculation is as follows:
Example: Seat Leon TSI 1.4 2009
- Displacement: 1.390 cc
- Number of cylinders: 4
(1390 / 4)0,6 x 0,08 x 4 = 10,70
Important note: All current cars and motorcycles have four stroke engines, for which you have to use the value 0,08 that appears in the formula. If you want to perform this calculation for a two-stroke engine you have to use the value 0,11.
As a note of interest, the displacement of the engine divided by the number of cylinders is the unit displacement of the engine. A value used in engine engineering that represents the volume of a single cylinder. Which is obtained with the formula: π x (cylinder diameter²/4) x piston stroke. A common formula to obtain the volume of a cylinder. In the cylinder capacity, elements such as the combustion chamber or the rest of the cylinder as far as the cylinder head does not go down. piston.
Method 2
If you would like to calculate tax horses the old-fashioned way, the formula in which piston stroke and cylinder diameter are used is:
Using the same example as before: Seat Leon TSI 1.4 2009
- Cylinder diameter: 7,65 cm
- Piston stroke: 7,56 cm
- Number of cylinders: 4
(0,785 x 7,652 x 7,56)0,6 x 0,08 x 4= 10,70
And what about electric and rotary motors?
In the case of electric the calculation is much easier. Enough with divide the effective power by 5,152. This power is determined by the Ministry of Industry, Commerce and Tourism. It is obtained by adding the maximum powers maintained for 30 minutes of all the electric motors that the vehicle has.
As you may have already deduced, although the calculation is simpler, has the extra complication of having to find the effective power of the model in question. Something that does not come in the technical file of the vehicle and that the brands do not advertise either. This is a value that appears in the homologation sheet.
The advantage is that most municipalities are applying tax reductions for electric and hybrid vehicles. Normally a 75% discount is applied throughout the life of the vehicle for pure electric vehicles and for six years for hybrids and moved to GLP, NCG o LNG. But it is better that you consult the town hall that touches you, because it may be different.
The rotary motors they also have their own way of obtaining the fiscal horses and it is exactly the same as in electric motors. That is, divide the effective power by 5,152. However, there are currently very few cars with this type of engine.
Images 2,3 and 4 – GotCredit, Henry Burrows, Jordi Domènech i Arnau