4HP20 – 4-х скоростная автоматическая коробка передач для легковых автомобилей производства ZF Friedrichshafen AG. Начало производства -  1995. Устанавливалась на автомобили марок – Citro?n, Lancia, Mercedes-Benz, Peugeot, and Renault:

• 1995 – 2001 Peugeot 406 V6 3.0L
• 1996 – Mercedes-Benz Vito
• 1996 – Mercedes-Benz V-Class
• 1997 – 2001 Citro?n Xantia V6 3.0L
• 1997 – 2001 Citro?n XM V6 3.0L
• 1997 – 1999 Peugeot 605 V6 3.0L
• 1998 – 2002 Alfa Romeo 166 V6 2.5L, V6 3.0L
• 1998 – Lancia Kappa,Phedra V6 3.0L
• 1998 – Renault Laguna 3.0L
• 1998 – 2000 Matra 3.0L

Xantia with 1.8 and 2.0 litre petrol models and non turbo diesel models may be fitted with an optional 4-speed fully automatic gearbox type 4 HP 14.

This gearbox consist a torque converter, an epicyclic geartrain and hydraulically-operated clutches and brakes.

Somewhere at the midle of the year 1997 (in some coutries January 1998) was Xantia coupled to the all new 4 speed Auto-Active transmission type AL4. Developed by Citroen, Renault and Siemens, the Auto-Active gearbox benefits from the expertise of the three companies in the fields of production, self adaptability, electronics and fuzzy logic.

Fuzzy logic is a relative logic which is used to incorporate and process a large number of parameters, even if they are uncertain or contradictory, with calculation of their relative importance.

The control unit controls not only gear shifts, but also the converter. Lock-up is available on each gear which enables transmission of full engine torque without wheel spin. This system gives the Xantia models fitted with the Auto-Active gearbox low fuel consumption approaching those of manual gearbox vehicles.

The new Auto-Active transmission uses a stepped gate with a “shift-lock” safety in the PARK position and has three push buttons to activate a NORMAL, SPORT and SNOW programs. The advantage of using these driving programs is that they enable the driver to stay in the program which best suits the circumstances. In addition, the new dashboard has a gear gate display showing the gear and program selected.

The ECU is the heart of the new Auto-Active transmission receiving data from:

• The gearbox (vehicles speed, turbine speed, oil temperature, lock-up status and oil pressure).
• The engine ECU (rpm, load, torque).
• The program selector and the pushbuttons (sport, snow, normal).
• The brake pedal stop light switch.
• The accelerator pedal position.

It uses the following 10 shift mode laws to adapt functioning of the gearbox to the driver’s driving style, to the program chosen, interior conditions (transmission temperature and pressure, …) and exterior conditions (road contours, grip, vehicle load, acceleration or deceleration…):

• “Eco” Law: Driving style favouring low consumption and a driving style for which the engine load is stable.
• “Medium” Law: Mixed driving style with emphasis on the engine speed mid-range.
• “Sport” Law: Driving style emphasising high engine speeds and using all of the engine’s potential (possibility of manual selection).
• “Gradient 1″ Law: Driving on an average gradient.
• “Gradient 2″ Law: Driving on a steep gradient.
• “Descent” Law: Driving using the engine brake.
• “Snow” Law: Driving on a slippery surface avoiding harsh braking (manual selection).
• “Engine Cold” Law: Driving emphasising low or intermediate engine speeds with engine cold.

To these 8 laws, we can add:

• Cold weather functioning law (not locked up) up to 15g.
• High Transmission oil temperature functioning, as from 1300.

This completely new transmission gives the Xantia driver control without the constraints. The Auto-Active box adapts to the driver’s every whim. He may chose in favour of economy or opt for a more sporty driving style and faster acceleration. The Auto-Active offers numerous possibility combining the relaxation and comfort of conventional automatic gearboxes with “driving pleasure”.