VW Fuel Injection System Types

by Jim Thompson

Quotes from the Bentley/Probst "Bosch Fuel Injection & Engine Management Manual:

D-Jetronic: The first Bosch Jetronic System. The D is short for Druck, the German word for pressure. Manifold pressure is measured to indicate the engine load (how much air the engine is using). This pressure is an input signal to the control unit (ECU) for calculation of the correct amount of fuel delivery.

L-Jetronic: The L is short for Luft, the German word for air. Air flow into the engine is measured by an air-flow sensor with a movable vane to indicate the engine load.....L-Jetronic was often called Air-Flow Controlled (AFC) injection to further separate it from the pressure-controlled D-Jetronic.

(My note: "Digijet" is the same as L-Jetronic with a few VW add-ons. It's a licensed system from Bosch).

LH-Jetronic: LH-Jetronic measures air mass (weight of air) with a hot-wire sensor instead of measuring air flow with an air vane (volume of air) as in L-Jetronic. Otherwise, L and LH systems are very similar. The H is short for Heiss, the German word for hot.

K-Ketronic: The first continuous system. Bosch called it a K, for Kontinuerlich, the German word for continuous. Air flow is measured by a circular plate in the air-flow sensor. Until 1980, fuel delivery is strictly under mechanical control in direct relationship to air flow; there are no electronics.....Volkswagen, Audi and Mercedes call this CIS.

KE-Jetronic: This combines K-Jetronic mechanical control with total electronic modulation of the mixture. It uses many of the sames sensors used in L-Jetronic systems. Because it is based on K-Jetronic, it is still capable of fail-safe mechanical operation if the electronics fail....Volkswagen, Audi and Mercedes called it CIS-E

Motronic: The first "engine-management" system. It combines L-Jetronic pulsed fuel injection with electronic ignition timing control in one control unit. In most engines, it also has electronic idle stabilization for a complete engine-management system.

Volkswagen Digifant: This pulsed system was partly designed by Volkswagen, but operates pretty much as Bosch Motronic does. It's timing control is less complicated than the Bosch Motronic map. It does not have a knock sensor.

(My note: VW Digifant II does have a knock sensor.)

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