The “Lexus” Traction Control (TRAC) System

Paper #:
  • 900212

  • 1990-02-01
  • 10.4271/900212
Ise, K., Fujita, K., Inoue, Y., and Masutomi, S., "The “Lexus” Traction Control (TRAC) System," SAE Technical Paper 900212, 1990, doi:10.4271/900212.
One of the innovations for the Lexus LS400 is the development of a traction control system (TRAC system). The TRAC system suppresses the spinning of the driven wheels, which occurs easily on slippery roads during excessive acceleration, and it improves the acceleration performance and the stability of the car.

The TRAC system controls the engine sub-throttle angle and the brake hydraulic pressure for the driven wheels in the same way as the traction control system for the 1987 Toyota Crown. But, acceleration performance and stability of Lexus LS400 is better than Crown as a result of good wheel spinning control by additional improvements of the throttle and brake control methods. Especially as the TRAC system controls the brake hydraulic pressure individually for left and right wheel, the car acceleration performance on split-μ surfaces is improved notably.

In regard to the system composition, low costs and simplicity have been targeted by using components of the ABS, while the TRAC system is designed according to redundancy concept using two-valve type throttle body which gives satisfactory result in the Crown TRAC system.

The TRAC system has been evaluated in the northern part of the USA, in Alaska, Canada, Sweden, Hokkaido (Japan), etc., and excellent car operation performance and high reliability have been confirmed.

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