Steve (old git) has asked me to calm down & post this & don’t get into battles with your founder. He is confusing his units & is a case of little knowledge is worse than none. I don’t make this stuff up its maths & is always correct.
Horsepower & Torque will always cross at 5252.1 rpm.
That's a fact that occurs regarding horsepower and torque they cross & are equal at 5252.1 rpm.
I will try to explain it the best I can.
To begin, we should start with gentleman named James Watt. He is the one who developed the entire idea of a "horsepower" and of course, the SI unit of power, the watt.
Watt sugested that the average horse could do work at a rate 550 foot lbs per second, or 33,000 foot lbs per minute. This means that on average, a horse could move 33,000 lbs 1 foot in 1 minute. So 1 hp=33,000 foot lbs per minute.
Now, since we're talking about engines, work is being applied to a rotating crankshaft. This means that we need to talk about torque. But what does a ft-lb of torque mean? Well, it means that we have a 1 lb weight attached to a weightless bar 1 foot from the fulcrum.
Now imagine that we rotate that bar an entire rotation, 360 degrees. The distance traveled is the circumference of the circle made, which is 2*radius*pi, which equals 6.28319 ft. So the distance traveled in one rotation is 6.28319 ft and so 6.28319 ft-lbs of work (torque) was done.
Now let's go back to Watt's equations for hp. Watt figured out that 33,000 ft-lbs of work per minute equals 1 hp. If we divide 33,000 by 6.28319, we get 5,252.1. This means that for every 5,252 revolutions per minute of 1 ft-lb of torque, we get 1 hp.
So a dyno measures Torque & then uses the equation to calculate horsepower.
