Technical Jargon - RPM vs BHP

Getting to know common Technical Jargon



Technical Jargon: Much confusion amongst the different power factors.

There are three common areas of confusion when one is caught up in the world of electronics or the auto trade:

  • Shaft, BHP,  Horsepower and Torque
  • Peak Music Power, RMS Power, Continuous Power
  • VA ratings compared to Watts

In the real world most of us mere mortals don’t like to base our preferences on advertising hype or opinions of others. In fact, if I am like others, we actually switch off when an individual boasts about the performance of his car over your own or others.  Discussions on motorcycles bring about the worst in us – so what if the Hayabusa is or was the fastest street bike. So what if that Rotel amplifier has more power than my Yamaha. So what if the Focus outperforms my Polo.

I work in the electronics and computer sector. The biggest mistake one can make is to assume that the end-user is a dunce because (a) you don’t know the person and (b) many end-users do research on a product before requesting guidance from the sales person.

An electrician friend of mine overheard a sales person telling a young couple in the process of purchasing an audio system for their home that the amplifier developed 150W of Real Mean Sound, a friend of mine told a client that his transceiver and antenna system had a problem with the Signal Warning Resistance and even worse, in my younger years my brother believed the car engine ran in reverse to push the car backwards. I was a total lover of Popular Mechanics, reading it religiously through the month until the next one arrived, like Practical Wireless, Popular Electronics, ETI and Elektor. The problem here is that you need to know what the abbreviations and technical jargon means before trying to impress someone with your gift of knowledge. Along came the computer and I more less saw the demise of any terms used by the IEEE (The Institute of Electrical and Electronics Engineers) or lesser so, The Society of Automotive Engineers. Our knowledge tree was ruined. So many abbreviations, so many the same but all with different meanings.

A bigger problem when it comes to technical jargon is whether it is used in the correct context or not. We pick this up especially when doing comparisons between the Mac and the PC, petrol versus diesel, watt versus VA, Class D versus Class AB and a very common – identifying which camera has the best pixels. We need to start at the very beginning.

Torque vs Horsepower

I use imperial here although of course a direct conversion can be made to metric.

Horsepower = power. Equal to lifting 33 000 pounds one foot in one minute.

Torque = rotational force. Torque is the measure of force applied to produce a rotational motion measured in pound-foot. If you want to be clever: One pound-foot = 1.3558179483314004 newton meters.

There are many trains of thought here – ft/lbs, ft-lbs, lbs/ft or lbs-ft? I only use lbs-foot (Pounds-foot) or N.m (Newton-meter). Be cautious of interchanging the lbs-ft with ft-lbs. See below.

Always ensure that there is no ambiguity in the way you have defined either torque or horsepower figures because there is another interesting aspect to all of this technical jargon at play here: Work!

Two things to remember: Work and Torque are not the same. HP is not independent of torque.

Technical Jargon - RPM vs BHP
Powerbands for different engine types. Source: Wiki

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