Bosch CIS (K-Jetronic) Fuel Injection Upgrade

Retro-fitting CIS Injection To An Air-Cooled Type-4.


    This series of pages is going to be an on-going update of my latest project for the bus.  I'm making two major up-grades simultaneously; I'm moving up to a 2000cc (2.0L) type-4 motor and I'm adapting the Bosch CIS fuel injection system to fit this new motor.

    Some of you out there may be wondering why??  Well, the answer is simple, I need more power.  The 1776cc I've been running is a great motor with good power, but it's taxed when I've got the family all in and we're going camping.  Now add the extra weight of my trailer loaded, and you've got a vehicle which has a hard time getting up hills and takes a fair bit of road to get up to cruising speed.

    I'd also like the added torque that only a type-4 engine can provide.  But, I want it smooth and as close to maintenance free as possible.  So my new motor is a 2.0L type-4 w/ hydraulically adjusted valves.  Originally, I bought a set of dual Dellorto 36 DRLA carbs, but decided I wanted to go a different, more high-tech and efficient route. . . 


    The acronym CIS stands for "Continuous Injection System".  This is a primarily MECHANICAL fuel injection system produced by Bosch  and widely used on many European cars from the 70s and early 80s including VW, BMW, Volvo, Mercedes, Porsche, Ferrari and the list goes on.  In a typical electronic fuel injection system (EFI) the fuel is pulsed at the injector by electrical signals from a computer brain box which gets it's info on fuel requirements through the use of a myriad of electronic engine sensors.  In the Bosch CIS system, the injectors are continuously injecting fuel into the manifolds.  Fuel requirements are metered by a simple and mechanical air flow box.   The more air that's allowed into the engine, the more fuel that is flowed to the injectors through the use of a fuel metering block.  To find out exactly how the Bosch CIS (K-Jetronic) fuel injection system works, check out these links:

    One of the advantages to CIS is that it is very simple and very reliable.  For me, simple is the name of the game.  I wouldn't even want to try and diagnose problems on a complicated EFI system since electrical things make me nervous.  Since this is a current project that is being tinkered with in my spare time, progress could be slow so I'm just going to make up-dates to this page as I make progress.

NOTE:  I will be keeping a running tab on the money spent on this CIS conversion so that those of you who want to try this yourself will have an idea how much you can expect to pay to put a system like this together at home.  I am notoriously CHEAP and actively seek out cheaper parts alternatives.  Most of the parts used in this conversion will be right out of the local pick-n-pull.  Look for the cost at the bottom of each stage of fabrication.

Intake Manifolds - Modifying a set of stock '72-'74 bus dual carburetor manifolds to hold the CIS injectors. Step-By-Step

Intake Plenum - Fabricating a custom air plenum and runners to go on top of the manifolds. CURRENTLY IN-WORK

Custom Length Fuel Hose - Making a custom banjo to connect two separate hoses into a custom length hose.  Step-By-Step


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Revised: August 23, 2003 .