Who has never been confused by different power values for the same car?
In practice, the most common mistake turns out to be not converting the values of hp and bhp for cv (Sometimes, even we make this mistake). Although it doesn't make a big difference in models with little power, in engines with great power this discrepancy ends up making the difference.
For example, 100 hp corresponds, after rounding, to 99 hp, but if it is 1000 hp, it equals “only” 986 hp.
The five units of measure
PS — Abbreviation of the German word “Pferdestärke”, which means “horsepower”. The value is measured according to the German standard DIN 70020, and differs slightly from hp (horse power) in that it is based on the metric system rather than the imperial system.hp (horse power) — Value measured on the drive shaft, with the necessary accessories to connect it and operate autonomously.
bhp (brake horse power) — Value measured according to the American standards SAE J245 and J 1995 (now obsolete), which allowed removing the air filter, alternator, power steering pump and starter motor, in addition to allowing the use of dimensioned exhaust manifolds. Without these losses, this was the preferred unit of manufacturers who “sold power”.
cv (cheval vapeur) 'As you can imagine, 'Pferdestärke' was not exactly an easy name to pronounce. That's why the French invented the cv (cheval vapeur), which is basically the same as the unit of measure PS.
kW — Standard unit of the International System of Measurements (SI), defined by the International Organization for Standardization (ISO) according to ISO 31 and ISO 1000 standards.
kW is the absolute reference
Using the standard kW unit as a reference, allows you to check the difference between our horses and others. Thus, in quantitative terms, the measurement units are distinguished as follows:
1 hp = 0.7457 kW
1 hp (or PS) = 0.7355 kW
1 hp = 1.0138 hp (or PS)
As a rule, kW is the standard measure used by most European brands (in particular German brands) in their technical data sheets, while American manufacturers prefer horsepower (hp).
Just for the sake of convenience — and even marketing — we still use the “horse” to define the power of an engine. It is always easier to “sell” a Bugatti Veyron with 1001 hp than with 736 kW.