In this technical article, we'll try to explain in a very simple way some interesting theoretical concepts related to the power and torque of our engine.
The engine is an air pump
“It runs on air, not gasoline.” I've repeated this phrase countless times throughout my career as a technical instructor. By inertia, we tend to think that the internal combustion engine runs on gasoline, and therefore, more gasoline means more power, but this isn't entirely correct. In reality, the engine produces power (work) due to the heat released when burning the air it contains (combustion). Gasoline is merely the "tool" for burning this air. Therefore, when we're looking for power, the first thing we need to focus on is increasing the amount of air entering and exiting the engine and the heat generated by burning it.
How to increase potency
Taking into account the above principles, we could say that there are 4 main ways to improve the power generated by an internal combustion engine:
-The air inlet and outlet can be modified to allow for greater airflow. For example, a higher-flow filter or a high-performance exhaust can be installed.
-The combustion chamber or ignition can be modified to improve combustion efficiency and generate more heat (which expands the air more and produces more work). An example would be the installation of improved cylinder heads or a racing ignition .
-Another more complex approach is to modify the engine to improve heat transfer and reduce friction. For example, by using cylinders with special covers or heat-shrinking the exhausts.
-Finally, a very effective way to improve power is to increase the cylinder displacement by installing larger pistons ( Big Bore ) or a crankshaft with more travel (Stroker).
Power and torque
We often confuse these two terms or don't give them the importance they deserve. Torque is the force that causes a vehicle to change speed, that is, the force capable of accelerating the vehicle. Power, on the other hand, is the engine's ability to maintain work at a given rate. Imagine 10 heavy boxes needing to be lifted up a flight of stairs. One engine lifts them in 10 minutes, and another engine, with twice the power, would lift them in 5 minutes.
Engine Torque is directly responsible for the power achieved, and the faster the engine spins (RPM), the more power.
This is why low-torque sportbikes need more than 10,000 RPM to deliver maximum power, while an American twin-cylinder engine delivers its maximum power at just a few thousand RPM.
To put it another way: Torque allows us to accelerate to a certain speed, and Power allows us to maintain that speed.
Differences between engines
So what's more interesting, having good torque at low RPM or a lot of power at high RPM?
Have you ever noticed how GP motorcycles in training require a little extra effort to gain speed when they start from a standstill at low RPM?
It depends on what we are looking for: if we like to go crouched under a fairing at very high speeds we will look for high revolutions for maximum power, and although we will not have much torque we will not need it because we have an aerodynamic assembly.
Now, if we enjoy pure acceleration, that never-ending "kick in the ass" when we open the throttle and feel the thrust and raw power from very low RPM, then Torque is our thing.
High-power engines typically have short strokes and wide pistons to achieve high RPMs. High-torque engines typically have long strokes and long pistons, applying more leverage and therefore more force to the crankshaft.
How do we do it?
Keeping the above theory in mind, it's important to carefully plan the steps to follow when trying to increase the "playfulness" of our engine. Many users and professionals install high-power kits that force the engine to run at high RPMs when, in reality, they're looking for more torque, which would be achieved with another type of modification. Therefore, it's important to seek good advice and understand the effects of engine modifications to achieve the desired results.
However, when we talk about American twin-cylinder engines or similar, the truth is that it is quite easy to considerably increase the torque (and in turn the power), since due to strict regulations they come very "watered down" from the factory.
For this type of engine, we're interested in some modification that provides the flattest possible torque curve, resulting in an engine with plenty of power and useful capacity at any RPM range, making driving easy and fun.
To enhance and enjoy, that is the question.
Frank Burguera
Article taken from ChoperOn magazine
0 comments