Understanding Horsepower and Torque

[moparfwdsleeper]

This is to help people understand the relationship and math between torque and horsepower.

Author: 86-89 Lancer

Here are some basic facts

1. The formula is: Torque x RPM / 5252 = Horsepower

2. Torque is the amount of twisting force the engine makes.

3. Horsepower is about speed or measuring how fast you get things done.

4. Horsepower is not a direct measurement; it has to be calculated by measuring TORQUE and RPM.

5. If you have big numbers (torque & rpm) you get big horsepower, if you have small numbers you get small horsepower; it is a numbers game in every way.

6. The number 5252 is very important besides being the formula constant.

For example:

• 5252 / 5252 = 1 that’s easy math, but read into it and you see in the formula that
  Torque x 5252 / 5252 = Hp
  They cancel each other out resulting in Torque x 1 = Horsepower; meaning that 300lbs of Torque = 300 Hp.
  
• On the graph Torque & Horsepower intersect at 5252 rpm, they always do – mathematical fact.
  
• Now we read deeper into 5252 with simple math: 4000 / 5252 < 1 so at 4000 rpm you’re multiplying torque by less than 1 and therefore have less Hp in the end.
  300lbs x 4,000 rpm / 5252 = 228.48 Hp see, you started 300 and ended with 228
  
• Fear not, Horsepower doesn’t always loose to torque, you have only seen examples below 5252 rpm, but now when we rev up and go above 5252 rpm the table turns and Horsepower rules the equations. 6000 / 5252 > 1 at 6000 rpm you’re multiplying torque by more than 1 and get more Hp in the end
  300lbs x 6,000 rpm / 5252= 342.72 Hp you started with 300 and ended with 342

7. From this all this we can conclude that:

• [5252 rpm is a crossing point
  
• Below 5252 rpm Torque will always be greater
  
• Above 5252 rpm Hp will always be greater

8. Because Horsepower is a numbers game it can be very misleading: 500Hp @10,000 rpm is very different from 500Hp @ 6,000 rpm. To figure out what the torque would be on both engines we need to solve for X (torque) by reversing the equation which would be Hp x 5252 / RPM = Torque

• The first engine with 500Hp @10,000 rpm only makes 262.6 lbs of torque but
  
• The second engine’s 500 Hp @ 6,000 rpm makes 437.66 lbs of torque that’s 175 lbs more and a way better engine

Hopefully you grasp these concepts and will no longer be fooled by bar room horsepower talk; Gook luck and happy calculating