Differentials

How the Magic of Mechanics Enhances Performance

In the world of automotive performance, we often talk about engine power, braking, or suspension. Yet, there is one discreet but essential mechanical component that works tirelessly to give you optimal grip and stability: the differential. At WOT, as performance specialists, we know the differential is much more than just a gearbox; it's a conductor, orchestrating how power reaches the ground.

Why is a differential essential?

Imagine your car going through a turn. The outside wheel travels a greater distance than the inside wheel. Therefore, to turn properly, the outside wheel must rotate faster than the inside wheel.

Without a differential, both wheels on the same axle would be locked together, spinning at the same speed. This would cause major issues:

• The inside wheel would have to "slip" to compensate for the difference in distance, leading to a loss of grip.
  
  

• The car would become difficult to handle, with an increased risk of understeer or oversteer.
  
  

• Tires would wear abnormally, and mechanical stress on the axle would be excessive.
  
  

The "open" (standard) differential solves this issue. It’s a set of gears that allows the wheels to rotate at different speeds. It distributes torque equally to both wheels but sends power to the wheel with the least resistance.

The Problem with the "Open" Differential: Loss of Traction

This is where the limitation of the open differential becomes clear. In a tight corner, under hard acceleration or on a slippery surface, the inner wheel—lightly loaded—can lose grip. The differential, by design, will then send nearly all the torque to that slipping wheel, while the other wheel, which still has grip, receives none. The result: loss of traction and inefficient acceleration.

To solve this problem, engineers developed the Limited-Slip Differential (LSD), designed to prevent this power loss.

Locking the Differential: The Key to Performance

The principle behind a limited-slip differential is to transfer torque to the wheel that has grip, preventing the other from spinning freely. There are several ways to achieve this:

• Mechanical Locking:
  Mechanical LSDs use clutch packs or Torsen gears to control slip. When one wheel starts spinning, the difference in speed between the axles activates a mechanism that "locks" the wheels together to a certain degree (e.g., 25% or 40% lock). This is a robust and predictable solution, favored in motorsport.
  
  

• Electronic Locking (via braking):
  This system, often confused with an active differential, is a simulation of LSD. It uses the car’s onboard electronics and braking system. When ABS sensors detect wheelspin, the electronics apply light braking to that wheel. This creates resistance and forces the open differential to send torque to the other wheel. It’s effective but reactive (acts after slip occurs) and can cause brake overheating under intense use. This is the principle behind Volkswagen’s XDS system or the e-diff found in many modern vehicles.
  
  

• Active Differential (electronically controlled):
  This is the top-tier solution. The active differential is a full mechanical system controlled by a dedicated ECU. It includes a multi-plate clutch that can continuously vary the lock level from 0 to 100%. Unlike braking systems, it’s proactive—it anticipates traction needs by analyzing vehicle data (steering angle, throttle position, G-force) and locks before wheelspin occurs. This is the system of choice in performance vehicles, such as Porsche’s Porsche Torque Vectoring Plus.
  
  

WOT Expertise: Managing Power for Maximum Efficiency

At WOT, our job is not to reprogram the differential calibration itself, but to adjust the torque flow being sent to it. This precise power management is crucial for performance, especially in two-wheel-drive (2WD) vehicles.

• Smoothing the torque curve:
  A sudden and massive torque surge in the lower gears can literally "cripple" a car’s performance. The power is so high that the wheels spin, triggering the onboard electronics (traction control, ESP) which cut acceleration and hurt performance. Our expertise allows us to smooth the torque delivery, making it more progressive and usable, ensuring smoother acceleration and better traction.
  
  

• Restricting torque in lower gears:
  Another approach is to deliberately limit torque in the lower gears. This maximizes traction by avoiding excessive wheelspin. The engine then unleashes its full torque and power potential in the higher gears, where grip is sufficient to transfer it effectively to the road.
  
  

The ultimate goal of our work is to transform raw engine power into usable and efficient performance on the road. A great engine in a car with poorly managed differential behavior will see much of its performance wasted in wheelspin. By finely tuning the engine calibration, we ensure that power reaches the ground in the smartest way possible, for a driving experience that is both faster and safer.