DiGuru said:
While cars are advertized with having a certain amount of horsepower, that is losing significance all the time.
It isn't.
Why are you claiming that it is losing significance?
Wouldn't it be better to state the amount of torque instead? Because horsepower is only interesting for the top speed, and has no real relevance without taking the weight and air friction of the car into acccount. And just about all of them will go much faster than the speed you can (normally) ever drive it in any case.
Torque is about fast acceleration and towing.
Torque is about towing. But Horsepower is about acceleration.
Just compare a lot of car specs and you will see that a car with more horsepower but less torque will accelerate faster than a car with more torque but less horsepower. (0-100 km/h)
And turbo charged, diesel and electric engines have so much more torque than normally aspirated gasoline engines for the same amount of maximum horsepower, that it is close to ridiculous. Twice the amount, in general. And at low rpm (or any, for electric), so that skews the picture even futher.
A car with twice the amount of torque and the same weigth will accelerate roughly twice as fast. And that's nowadays just about the only thing you notice or care about, power wise.
So you are comparing a 3 liter turbo charged diesel engine to a 2 liter gasoline engine, (otherwise you won't get the same amount of horsepower) and then you are suprised that the diesel wins?
You are comparing apples to vigs. (not oranges because your comparison is too far off for that...)
Compare a modern 2 liter diesel to a 2 liter gasoline engine and you will see that the diesel will have more torque, but the gasoline will have more horsepower.
Also the diesel will be more expensive, and will have an economical lifespan of 250.000 km while the gasoline engine will last 500.000 km.
Of course if you compare it with a diesel engine that costs twice as much, the gasoline will loose.
Then back to your original statement that torque tells you more about performance:
It is simply wrong!
Torque tells you ABSOLUTELY NOTHING about the performance of your car.
Torque only becomes a meaningful value when you know at what rpm it is produced, and what the maximum rpm of a car is. The maximum power of the engine is then determined by multiplying Torque with rpm.
Let me give an example:
An engine with a Torque of "4" with a rpm of 2000 will have a maximum "power" of 8000
An engine with a Torque of "2" with a rpm of 5000 will have a maximum power of 10.000
As most people will know, gasoline engines have lower torque, but use higher rpm. Because of this, the engine can produce just as much power as a diesel engine.
So this "power" value is a far better value to compare engines with.
And not suprisingly this "power" value is the amount of HORSEPOWER of an engine.
And that is why HORSEPOWER is usually used to compare engines.
There is an exception to all this though: Towing.
If you need to move a heavy load, then you start from 0 rpm. You cannot compensate for lower torque by using higher rpm, because you don't move fast yet.
So to get a large load moving, a high torque value is important.
(Although you can compensate for that with different gearbox ratio,s but lets not make this too complicated)
There is a different torque value that would actually be interesting: The torque on the wheel axis.
The rpm value doesn't play a role here anymore, because the rpm for accelerating from 0 - 100 km/h is the same between cars. (as long as the wheels have the same size)
You then also take the gearbox and other factors into account.
Unfortunately those numbers are almost never included in the specs of a car.
I have found that many people do not truly understand what torque and HP means. So I advice everybody here to read the following page:
http://www.squadra-tuning.com/English/EN_what_is_torque_and_performance.htm
It explains clearly what it means, and what the graphs you see in the specs of cars tell you.