India’s automotive market took the first step earlier this decade and has not looked back. These vehicles have so much performance that they can’t be compared with their predecessors, which were launched a decade ago or even a few decades ago. While electronic vehicles have made some improvements, there are still some automobile laws that remain the same. Even though vehicles have become more powerful, many owners aren’t able to fully utilize their potential due to a lack of knowledge about technical aspects. We thought it would be a good idea to help our readers understand the technical details of a powertrain so they can get the most out of their vehicle.
Remember the famous drag race between Vin Diesel (in Dodge Charger), and Paul Walker (in Toyota Supra), across the railway line. This is one race we will never forget. While we all know the basics of the accelerator, clutch, and gear, what about the physics? I can think of the drag race in “Need For Speed”, where players toggle between the gears as soon as a green light appears on the dashboard.
The main considerations when buying a car or motorcycle are engine power, space and fuel economy. However, almost everyone overlooks the torque component of an engine. The engine’s torque output determines the vehicle’s pulling power. This is the principle of ‘green lights.
Explaining with Formula:
We know Force (F) = Mass x Acceleration(A).
Because the vehicle’s mass is constant, acceleration is directly proportional to its force (here, tractive force). A vehicle’s traction force (exerted on the road by tires) is maximal when it generates maximum torque. This makes acceleration directly dependent upon engine torque. Every engine produces power and torque. However, the beauty of a traditional power-torque curve (see below) is that power can only be obtained at high speeds, and this too in a narrow band. While torque can be generated at lower speeds over a wider range, it is more consistent.
Explanation: The Hyundai i20 produces 90 P.S. at 4000 RPM, while the engine generates 225 Nm torque between 1500-2750RPM.
The plotted graph, also known as a saw profile curve, shows vehicle performance. It plots engine speed and vehicle speeds for each gear.
As stated above, torque refers to the pulling power of a vehicle. The vehicle achieves the best acceleration when gears are changed in the maximum torque band (yellow).
The engine speed drops when the driver puts their foot off the accelerator pedal. After applying the clutch and changing to the next gear, the clutch is applied. If the engine torque band is at its maximum limit (A1, B1, C1, and D1), the engine speed will drop to (A2, B2, C2, or D2) speeds. However, the engine torque band will remain the same. After gear shifting, the vehicle will use all the torque from the engine. This will allow for the best acceleration.
It takes technically more to switch between lower gears (A1->A2; B1->B2) than between higher gears (C1->C2; D1->D2). The gear shifts’ timing determines how much engine speed drops. Many cars have the famous 1.3-litre MultiJet diesel engine from Fiat. It doesn’t accelerate below 2250 RPM because the turbo lag means the engine doesn’t produce enough torque.
P.S. P.S. – This article does not encourage drag racing but is meant to help our readers understand the mechanics behind the pedal and gear knob. Both cars and bikes can use the same principles.