Why does CIS (K-Jetronic KE-Jetronic ect.)need individual fuel lines to each injector? Could it work with one fuel line from the fuel distributor to an injector rail? Just curious, the thought just sort of popped into my head like the Sta-Puft marshmallow man.
Wouldn't you be injecting fuel all the time though?
The injectors open with the pressure sent from the fuel distributor. They are mechanical.
The injector is just a nozzle. CI means continuous injection, so the fuel is constantly flowing through the injector. It builds a little ball of fuel vapour right by the intake valve through the squeeze, bang and blow cycles, then sucks it all in.
I suppose you could run one line from a larger port to a series of injectors, but it would be very difficult to keep it balanced from cylinder to cylinder. It's tough enough to do with individual injectors.
My thought is it's easier to get the injectors balanced in the fuel distributor than deal with the pressure differences in a fuel rail. There may be insight in one of the old CIS books. Every mechanical system has individual lines from whatever their metering block is, now that I think about it.
The fuel distributor has individual metering ports to each injector, the magic to the system is in the fuel distributor. How would you meter the fuel on a common rail? Something tells me you'd end up with lean and fat cylinders because the fuel would take the path of least resistance through whichever injector opened first. Would fuel pressure be consistent through the rail?
benzbaronDaryn said:Would fuel pressure be consistent through the rail?
Vapor lock would probably be bad too.
Noddaz said:Why does CIS (K-Jetronic KE-Jetronic ect.)need individual fuel lines to each injector? Could it work with one fuel line from the fuel distributor to an injector rail? Just curious, the thought just sort of popped into my head like the Sta-Puft marshmallow man.
It probably could. I also have a feeling that Bosch did not do that for two reasons: less chance for trapped air in a set of lines vs. a rail, and even the early electronic systems did not really have "fuel rails" that injectors plugged into, the injectors were mounted in the manifold and rubber hoses went to each injector.
Given that the injectors needed to be mounted as close as possible to the intake valves (minimizes wetted manifold area), and so they needed to run lines from the fuel distributor over to the intake anyway, may as well have 4 -8 discrete injector lines.
Another thing to consider is that K-jet and its derivatives were expensive to manufacture, and Bosch accordingly promoted it as the premium option compared to D-jet, and later L-jet. Mercedes and Porsche had K-jet, cheap VWs had D-jet. (Porsche used K jet until about 1994!) They were putting it on inline 5s and flat 6s and V8s, all largely with the same or very similar components, so in a way they could focus on making a better product by making the hard parts as universal as possible.
Paul_VR6 (Forum Supporter) said:benzbaronDaryn said:Would fuel pressure be consistent through the rail?
Vapor lock would probably be bad too.
Oh, lord, you don't want to try to start a kjet car with a failed residual pressure valve when it's hot.
The early Volvos had some issues, and the cheap solution was to wire up a pushbutton switch to the cold start injector. Crank the engine, hit the silver button, it flares up and clears the air from the injector lines.
Two most important parts- residual pressure valve and clean fuel.
In reply to Streetwiseguy :
So that's why Audi had a little fan to blow air over the fuel injectors in the 10 valve turbo engines.
I assume VW never saw a need on their transverse K-jet applications because the underhood geometry changed the heat soak characteristics. The Audis crammed things up against the hood with no airflow.
Pete. (l33t FS) said:In reply to Streetwiseguy :
So that's why Audi had a little fan to blow air over the fuel injectors in the 10 valve turbo engines.
I assume VW never saw a need on their transverse K-jet applications because the underhood geometry changed the heat soak characteristics. The Audis crammed things up against the hood with no airflow.
You have a pic of that fan? I would think the VW would be worse as the injectors sit closer to the firewall but maybe that is better w the hood vents right above than the Audi.
Do yall know anyone rebuilding fuel distributors at a reasonable price? Currently going through all the fuel system in my ke-jet 190e. I really need to do a standalone on this car already.
yupididit said:Do yall know anyone rebuilding fuel distributors at a reasonable price? Currently going through all the fuel system in my ke-jet 190e. I really need to do a standalone on this car already.
I've not used a rebuild service, but I know Salvox makes rebuilt kits for the Saab applications. I'd assume they have them for your Benz as well.
Paul_VR6 (Forum Supporter) said:Pete. (l33t FS) said:In reply to Streetwiseguy :
So that's why Audi had a little fan to blow air over the fuel injectors in the 10 valve turbo engines.
I assume VW never saw a need on their transverse K-jet applications because the underhood geometry changed the heat soak characteristics. The Audis crammed things up against the hood with no airflow.
You have a pic of that fan? I would think the VW would be worse as the injectors sit closer to the firewall but maybe that is better w the hood vents right above than the Audi.
No good ones unfortunately. As far as I know it was only the turbo applications, that had a turbo on one side of the intake, a wastegate on the other, right up against the hood, and the radiator fan was off to the other side of the engine bay.
yupididit said:Do yall know anyone rebuilding fuel distributors at a reasonable price? Currently going through all the fuel system in my ke-jet 190e. I really need to do a standalone on this car already.
I used CIS Flowtech back in 2016 or so for my 500SEL.
I also picked up a spare one from the junkyard and took it apart to see if I could rebuild it myself ... forget it lol!. I still find springs that went flying everywhere when I opened it up. There are two springs top and bottom of each valve on each port, I have no idea how in hell you reassemble that.
CIS flowtech is who everyone suggests to rebuild, but think you are talking $400. I would try the salvox kit myself, the problem is you cant really balance test it. The FD is supposed to be easier to rebuilt than the warmup regulator, but you gotta be meticulous.
I'm certainly not doing it myself. Tedious things makes me give up up on life then I end paying someone to do it in the end lol
benzbaronDaryn said:CIS flowtech is who everyone suggests to rebuild, but think you are talking $400. I would try the salvox kit myself, the problem is you cant really balance test it. The FD is supposed to be easier to rebuilt than the warmup regulator, but you gotta be meticulous.
To be honest $400 for a rebuild is not bad. I owned a VW that used CIS-E and when I finally got to the point where I knew how to tune it for racing, I ran in SCCA IT class, the fuel dist. took a dump!. There are no new 30 year old fuel dist. around so a rebuild is the only way. In my case a small fire in my garage damaged the car enough that I parted it out before I looked for a rebuild service.
Have you guys seent this before?
It's a couple of modules that work with the existing Bosch CIS and CIS-E (K-jet and KE-Jetronic) systems and allow for laptop tuning of the system.
I swore off german engineering years ago, but would consider it if I was still in the game.
https://dkubus.com/?product_cat=bosch-cis-and-cis-e-k-jet-and-ke-jetronic
In reply to CrustyRedXpress :
I know 5 or 6 people running FrankenCIS with success. You still have to build a microsquirt to use it.
It still uses the air flow system but manipulates the WUR to richen up the mixture. Just modifying the stock WUR and making it adjustable gets you most of the way there for a lot less. But in the end dumping the air flow plate and box lets the engine breath much better. Standalone let the engine make much more power.
I'd just as soon do the hack where you have an LC1 or similar with two programmable faux-narrowband outputs. Have one at 14.7, the other at your WOT ratio of choice, and use the WOT switch to control a relay that switches between the two. The control module stays in closed loop.
Back in the early aughts I rewrote some of the early ms1/extra code to do it. Just used a stock cis-lambda valve and allowed adjusable dc but fixed frequency. Worked well enough but ran out of fuel past too soon anyway.
Slippery said:yupididit said:Do yall know anyone rebuilding fuel distributors at a reasonable price? Currently going through all the fuel system in my ke-jet 190e. I really need to do a standalone on this car already.
I used CIS Flowtech back in 2016 or so for my 500SEL.
I also picked up a spare one from the junkyard and took it apart to see if I could rebuild it myself ... forget it lol!. I still find springs that went flying everywhere when I opened it up. There are two springs top and bottom of each valve on each port, I have no idea how in hell you reassemble that.
I would guess petroleum jelly. But that is only a guess.
I also add there is a very good Acura tech where I work that bought a DeLorean that didn't run because of the fuel distributor and general long time sitting malaise. He looked up some info online and bought a kit for the fuel distributor. He took it apart, cleaned it and re-assembled it. It worked. I was (and still am) impressed. He is a Chevy guy that works at Acura dealership and dived right in and fixed it. He claimed it wasn't going to fix itself.
I think I'll skip rebuilding the FD and start collecting parts for an EFI conversion. Even if I rebuild the entire CIS, I still will have an EZL that can poop at any moment. I have a few EZL spares but damn they're pricey used and you never know their condition.
If I could find a 3.6 M104 engine to swap in that would be the best idea. Even though I am pretty happy with the 3.0 M104 24v powerband.
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