Ps vs. HP

[Rick]

This question is directed at the mechanical and engine types. The Germans used Ps = Pferdestärke, loosely translated as Horse Power, to rate their engines. The British and Americans used HP = Horse Power. However, I seem to recall that 1 Ps is not equal to 1 HP, but is something like 1 Ps = 1.05 HP, or was it 1 HP = 1.05 Ps ??? I.E. what is the mathematical relationship between Ps and HP ?? (and, please don't get off on a big discussion about kW or kilo joules or whatever).

Thanks, Rick

[Romani]

Ps is the same as the French CV (Chevals Vapour = steam horses, metric horsepoer). And Imperial HP are greater, but I always forget the conversion ratio.

To make matters worse, I just discovered that in my reference book the translator made the mistake of replacing HP with CV, so the British engines are more powerful than I thought!


EDIT: here's the conversion ratio

1 HP = 1.014 metric CV or PS


So unless you are dealing with WWII engines, with 1000 HP or more, the difference is not significant.

[Rick]

Thanks, Romani, I appreciate that. Sounds to me, as you said, it's a wash. R.

[Dan_San_Abbott]

Rick:
The problem with using hp on German or French engines, mistates the rated power of the engines.For example 160hp Mercedes D.III is rating the engine as 98.6 Ps. The correct form is the Mercedes D.III engine is rated as 160 Ps @ 1400rpm. If you wish to use horsepower, it is 162.2 hp. The difference is not much, it is a matter of stating correct information. You will notice that in my text I have consistantly used Ps to define the power of the engines.
Blue skies,
Dan

[Romani]

*scratches head*

Ok, I didn't understand anything of the above, could you rephrase that again, Dan San?

I only know for certain that both are units of power, and that HP is greater than PS by a small ratio.

Now, are you saying that there are two measurements for CV or PS in a engine? Nominal one and maximum power output at a certain number of rpm or something like that?

Your figures seem to imply CV /Ps are greater than HP?

[rammjaeger]

Where did the Allieds measure the power of their engines? Close to the motor itself?

I read the 300 "SAE PS" of an American 65er Corvette were in fact only 230 DIN (German Industrial Norm)-PS. And that is significant ... *;D