CIS vs. D-Jetronic and L-Jetronic

I do think K-Jet without Lambda having absolutely no electronics is an amazing, and clever, achievement (and was a cost saver then). What about high RPM operation? The Probst book seems to put a limit of ~6K RPM on the pulsed systems. Not saying that an analog pulsed system couldn't be designed for higher RPM operation, but, if one wasn't available then from another application, maybe the non-recurring engineering cost that Bosch would've wanted to develop one was just too much to justify for a low-volume application -- just a thought...

 

K-jet has one plus above the others, it will run without an ECU. In it's simplest form being a hydrolic system it doesn't need an ECU to function. So limp home mode is dang close to normal operation. Was that the selling point to ferrari? No idea. But I don't think ferrari had much say in it. They are a botique builder of very low numbers, going to Bosch they are in need of a fuel system that meets emissions and one they can afford. More then likely given Mercedes volume production and that of Porsche both using k-jet... It was the cost effective option.

70's into the early 90's ferrari shared allot of parts with other mfg's... Cost is why and makes a lot of sense. Could have been worse... Could have been Lucas!

 

K-Jet CIS (and subsequently KE) was a perfectly good system for its time if correctly maintained. Multi million Mercedes-Benz, Porsche, VW, Volvo etc models over a relatively long production period can attest to this. Deferred or poor maintenance and lack of use doesn't do it any favours, but IMO it's unfairly maligned.

Bosch is a system developer. Ferrari in the late 70's were never going to bankroll a bespoke EFI system development on such limited production volume. As the previous posters had mentioned, K-Jet was a cost effective solution that would meet the emission / consumption requirements. D-Jet was already at the end of its development by this time and (I suspect) L-Jet was significantly more expensive.

Re. K-Jet replacement partx /rebuilding, in EU Bosch Automotive Tradition has put effort into ensuring fuel distributor metering units and warm up regulators can be officially refurbished in Nuremberg (and you have CIS FlowTech in US), and many K-Jet items such as fuel pumps, fuel accumulators, injectors are all still in production (in-house) at Bosch.

 

I have either owned or still own (36 years now with one) 6 cars with K jet.

I have never had a single problem with the CIS on any of them at any time. Ever.

Am I the exception?

 

I am kind of surprised at the OP as well (sorry to hear it has given them so much trouble). I have previously heard only good things about K-jet.

For my car, there are no records of CIS problems in the Service Records and no problems in my 8 years of ownership. Its been “set and forget” and passes California SMOG. I have open loop K-jet (‘83 QV).

Don’t forget Rolls Royce.

 

My L jet has never acted up on my Alfa either.

25 years now.

 

Their lack of complexity is their secret sauce.

 

Plain Jane k-jet is reliable. K-jet E .... More complexity brings more fussy issues.

EFI is just as reliable as k-jet and easier to work with.

Modern fuel with ethanol causes issues for k-jet. The issue is ethanol fuel does not share the same specific gravity or energy density as pure gasoline. The system is based on airflow pressures and density for pure gasoline, so ethanol fuel is not going to have the right ratio.

All stuff wears out and breaks down. I don't think k-jet is honestly any better then EFI in that regard. Both have injectors that fail, seals, filters etc..

For myself, EFI is simply the superior system though.

 

"You would think that by 1982 Ferrari would know that everything they build is collectable and so should be built somewhat concerned about the long term drivability of their cars 40 or 50 years down the road. Ferraris are not like Vegas or a K-cars, they are for fun and collecting, not for commuting."

Remember, at that time, Ferrari sold road cars to finance their race program. Enzo Ferrari stated that on several occasions, making clear his personal lack of interest in them. So there wasn't any concern about the drivability in 40 or 50 years...or, based on their warranty, much more than 40-50 weeks!

 

I think from the standpoint of Ferrari, or any manufacturer in 1980, the choice of a purely mechanical FI system was based on proven reliability. This stuff was not new, it had basically been around for 50 years and to this day most piston driven general aviation aircraft use the same basic type of constant, mechanically controlled injection due to it's reliability. In the automotive world much of this is driven by emissions standards. Even a crude carbureted Chevy small block runs clean at a constant cruise, it's only during cold starts or dropped throttle deceleration or enriched full throttle acceleration or hard cornering when the float level is upset that they get dirty so all the fancy electronics take care of all that.

But in regards to planned, or unplanned obsolescence I think it's the CPU's and other electronics that endanger us the most and this may become more evident as time marches on.

 

Yet even in 2021, I'm working on modern, mass-produced cars with direct injection that are so poorly designed that they need the throttle cleaned with a media blast before they've reached their 4th birthday.

IE - don't be too harsh to judge the decisions Ferrari made, especially given than so many of them are still running well (as-designed) 40 yrs later.

 

Hi Andy,
Going back your original post, I think if the K-Jet system is worn out and missing parts, you may as well upgrade to something more modern. The cost would probably be the same considering how inexpensive EFI parts are now days and that even though lots of 70's-80's cars had K-Jet systems, they are all tailored to the application (so cross matching parts is not that easy and either is finding some of these parts). How are going to fit the Holley system though? You will need a new custom intake manifold as the Holley is 4bbl throttle body! Quite a few people on the forum who have gone down this road have modified the OEM Ferrari intake to take electronic injectors and a modern throttle body. They are the two biggest hurdles - once overcome the rest is pretty straight forward. Choose your aftermarket ECU, some sensor wiring and a dyno tune!

 

Or a manifold that holds a pair of them....a tunnel ram with dual quads would looks kind of cool...wrong of course, but kind of cool.

The mounting is the issue though....is it going up on top of the engine? I don't think there is room for that and a workable plenum on top of the stock TUNED length runners? So cut the runners or cut the hood.....just doesn't seems like a very easy to install option unless cutting the hood is the plan.