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Toyota Electronic Modulated Suspension

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TEMS (Toyota Electronic Modulated Suspension) was a shock absorber that was electronically controlled based on multiple factors, and was built and exclusively used by Toyota for selected products during the 1980s and 1990s. The system was widely used on luxury and top sport trim packages on most of Toyota’s products sold internationally. Its popularity fell after the “bubble economy” as it was seen as an unnecessary expense to purchase and maintain, and remained in use on luxury or high performance sports cars.

Summary

TEMS consisted of four shock absorbers mounted at all four wheels, and could be used in either an automatic or driver selected mode based on the installation of the system used. The technology was installed on top-level Toyota products with four wheel independent suspension, labeled Pegasus (Precision Engineered Geometrically Advanced SUSpension). Because of the nature of the technology, TEMS could only be installed on vehicles with front and rear independent suspeensions.

Based on road conditions, the system would increase or decrease ride damping force for particular situations. The TEMS system was easily installed to suit ride comfort, and road handling stability on small suspensions, adding a level of ride modification found on larger, more expensive luxury vehicles.

As the Japanese recession of the early 1990s began to take effect, the system was seen as an unnecessary expense as buyers were less inclined to purchase products and services seen as “luxury” and more focused on basic needs. TEMS installation was still achieved on vehicles that were considered luxurious, like the Toyota Crown, Toyota Century, Toyota Aristo, and the Toyota Supra and Toyota Soarer sports cars.

Recently the technology has been installed on luxury minivans like the Toyota Alphard, Toyota Noah and the Toyota Voxy. The TEMS system has been recently named “Piezo TEMS”, “Skyhook TEMS” “Infinity TEMS” and more recently “AVS” (Adaptive Variable Suspension) on Lexus products

Configuration Settings

The system was deployed with an earlier two-stage switch labeled “Auto-Sport”, with a later modification of “Auto-Soft-Mid-Hard”. Some variations used a dial to specifically select the level of hardness to the driver’s desires. For most driving situations, the “Auto” selection was recommended. When the system was activated, an indicator light reflected the suspension setting selected. The system components consisted of a control switch, indicator light, four shock absorbers, shock absorber control actuator, shock absorber control computer, vehicle speed sensor, stop lamp switch, with a throttle position sensor and a steering angle sensor on TEMS three stage systems only.

Operation Parameters of TEMS

The following describes how the system would activate on the earlier version installed during the 1980s on two stage TEMS

  • During normal running 100 km/h (62.1 mph)

The system chooses the "SOFT" selection, to provide a softer ride.

  • At high speeds 85–100 km/h (52.8–62.1 mph)

The system selects the "HARD" selection and determines that at high speeds, it assumes a more rigid configuration for better ride stability, and to reduce roll tendencies.

  • Braking (reducing speed to 50 km/h (31.1 mph))

In order to prevent “nose dive”, the process proceeds to "HARD" automatically damping force until it senses the brakes to be at the"SOFT" setting. It will return to the "SOFT" state when the brake light is off, and the pedal has been released after 2 seconds or more.

  • (Only 3-stage systems) during hard acceleration

To suppress suspension “squat” the system switches to "HARD" based on accelerator pedal position and throttle position.

  • (Only 3-stage systems) during hard cornering

To suppress suspension “roll” the system switches to "HARD" based on steering angle sensor position.

  • SPORT mode

The system remains in the "HARD" position regardless of driving conditions. (For 3-stage systems, the system chooses the “MID” configuration)

Vehicles installed

The following is a list of vehicles in Japan that were installed with the technology. There may have been vehicles exported internationally that were also equipped.

See also

References

Development of New Toyota Electronic Modulated Suspension - Two Concepts for Semi-Active Suspension Control

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