The two are related by the formula HP = torque X RPM / 5252.

In other words if you tell me what the HP is at a given RPM, I can tell you what the torque is at that same RPM. All engines follow this formula.

It's not about torque versus HP, it's about the shape of the curve. At what RPM does the torque or HP peak and how flat is the curve.

Hope this helps.

My guess is that the 2.4 has a flatter curve. Makes more HP and Torque at the lower RPMs than the 2.0

 

So, in reality, these are very close to the SAME THING! :lmao: How's that for ya?

Not really. But Horsepower is a derived unit of the product of torque and RPM. RPM literally scales horsepower.

Torque is a measure of how much work you can do this instant. Snap your fingers and that sort of force is torque.

Power is a measure of how much work you can do over time. It is the summation of all of the 'torques' over a standard amount of time.

For instance, if you had a torque curve which is completely flat and has an identical torque at 1000 RPM as it does at 6000 RPM, the Horsepower at 1000 RPM will be 1/6th the horsepower at 6000 RPM. Very simple concept there, right?

The way a normal person can usually tell the difference between a 'torquey' motor and a 'power' motor is simply by looking at the tachometer. If you have no apparent acceleration until very high RPMs, you have a 'power' motor. If you get pushed back into your seat immediately, you have a 'torquey' motor.

The way you compare two engines to each other is then all about gearing. My Dad likes to say he used to be able to beat any car across an intersection in his VW bug. The thing was geared very low, had all of its engine over its rear wheels and was light as a feather. Even though it only had 37? HP, he said it would get the jump on many 4,000+ lb muscle cars. But only for the first 30 ft or so. Then all hope was lost as a car with 10 times the power just screamed on by.

Back on topic.

Gearing is the way to trade torque for RPM. It won't alter the amount of POWER you have available, but it will let two engines have an identical amount of output torque for an instant.

 

For instance, if you had a torque curve which is completely flat and has an identical torque at 1000 RPM as it does at 6000 RPM, the Horsepower at 1000 RPM will be 1/6th the horsepower at 6000 RPM. Very simple concept there, right?

Usually known as electric motors .... ?

 

'HP is how fast you hit the wall, torque is how far you move it'.

 

Your seat of the pants dyno detects torque. You never really feel horsepower. When a vehicle takes off like a rocket, that's a torque happy combo. Gearing will involve a torque modifier. A bad gear ratio combo can make a strong engine feel weak. A good gear ratio combo can make a so-so engine a lot of fun.

F1 teams spend millions every year on gear combo simulations. It can make or break your race, even if you are running a spec engine (which F1 does not).

 

Yeah I know I'm over simplifying and it's probably darn near impossible to have 160 torque in a 40HP engine.:thinking:

Nowhere near impossible! You just are talking about a totally different design of an engine. The engine of the Allis Chalmers WD45 tractor from the 1950s was rated at 39 HP at 1400 RPM. It developed 288 lb-ft of torque at 867 RPM. So, a lower speed, longer stroke engine provides more torque relative to HP. For comparison, the Model A engine produced 40 HP at 2200 RPM and 128 lb-ft of torque at 1000 RPM. Bill

 

Yeah! I mean an average person riding a bicycle can generate 160 ft-lb of torque while maxing out at ~1HP. That's a torquey engine for ya!

 

At work we have some seriously monstrous electric motors.

The largest weighs 40 tons, is 14 feet high , has a 20" solid steel shaft, water cooled with 4" pipes.

It's rated at 35 000 hp @ 1800 rpms. That's 102 000 foot lbs of torque, Or over 50 tons per foot of torque!

Operators have to call Hydro Quebec so they can be prepared for the dip they cause to the grid on start up.

.....and you thought diesel trains and top fuel dragsters were powerful machines.

 

.....and you thought diesel trains and top fuel dragsters were powerful machines.

Aren't most diesel locomotives diesel-electric anyways, with the electric motors actually doing the propulsion and the diesel engines just powering the generators for the electric power ?

I know there are some diesel-hydraulic locomotives as well but my impression is that they are in the minority ...?

It's all about the torque