KE Jetronic guide

Carbs at best give you kind of an approximation of the correct fuel mixture if the air density is right. Then every time you move the throttle plate it changes.
Fuel injection, even one as simple as CIS is vastly more precise ALL THE TIME.

Thats why carbs went the way of the dinosaur.

 

"Bosch Fuel Injection and Engine Management" by Charles O. Probst, published by Bentley. Readily available from Amazon or other booksellers. It has very clear and detailed explanations of all types of K-Jetronic systems, including KE-Jetronic.

 

This link will get your F's write-up for how Bosch KE-Jetronic with Lambda was/is implemented on US version TR:

https://www.dropbox.com/scl/fi/nnb2n9bnal3zbpmvyo972/Workshop-Manual-Testarossa-Supplement-Catalytic-Converter-D61-D106.pdf?rlkey=fmcxx9icmokt632mz2jg1c8hv&st=jxhdje2j&dl=0

This link will get you a Bosch general write-up on KE-Jetronic (but it has many "optional" features of KE-Jetronic that weren't implemented on TR):

https://www.dropbox.com/scl/fi/assdvaj7b0nq7h4gyx7du/Bosch-KE-Jetronic-Manual.pdf?rlkey=9kl5p78ghaqdaaut5vd2hm7vy&st=xq1f4weh&dl=0

My take on the Bosch CIS systems (and how they evolved over time) is:

Bosch K-Jetronic without Lambda is brilliant in its simplicity. No electronic ECU with only one iffy thermo-mechanical gizmo (the WUR), but not "clean" enough to meet emissions.

Bosch K-Jet with Lambda has lower emissions but is the most over-complicated of the group as it has a WUR, an electronic ECU, and a frequency valve.

The got smarter with KE-Jetronic (both with and without Lambda) as they figured out they didn't need a WUR so it only has an electronic ECU and EHA. However, the nominal EHA current is 10mA and swings from 0 ma (lean) to 20 mA (rich) so when the Protection Relay system fails the system goes lean and engine barely runs if at all).

They got even smarter on KE3-Jetronic as they changed the EHA current to nominally be 0 mA and swings from -10mA (lean) to +10mA (rich) -- so when the Protection Relay system fails the engine still runs OK. (They also raised all the various pressures which improves he overall efficiency of the system).

 

Not AFAIK. People have converted from CIS to an EFI systems, but it's a huge modification and amount of work (and rarely done in a way that I would call "undetectable to the layman").

 

When you say CIS was not clean enough to meet emissions? Well its the only reason many of those cars could be sold for several years. Emission standards got more strict. Then it was not clean enough but as good as many older systems were they wont pass now.

 

No question that K-Jet without Lambda was light-years better than a carburetor for emissions. I meant what you wrote -- it was darn good, but not good enough for what emission standards soon became (especially with the addition of cold-running/cold start-up emission specs).

 

That still a moving target, almost 50 years later.

 

It was a changeover at the time by the factory to meet emissions in other markets.

 

K-Jet is also unbelievably dependable. Of the 4 different VW's I have owned (and still own two) going back to 1985 and used as daily transportation for a tad over 20 years, it was the only part of the cars I never had to touch. Ever.

Same with my QV. 27 years and never an issue with it.