"Programable" options for the CIS crowd

[RonInSD]

I ran across this on another forum and figured I would pass it along to you VW CIS-Basic guys. The CIS-Lamda guys may be able to use MegaSquirt to control the frequency valve. Remember that the WUR is just a fuel pressure regulator.

http://unwiredtools.com/utcis.asp

To me it looks like an adjustable fuel pressure regulator with a stepper motor.

[GKR_17]

Remember that the WUR is just a fuel pressure regulator.

Are you sure? On the early CIS BMW's the WUR changes the resistance in the AFM, but does not directly control pressure. Not quite the same as a typical pressure regulator.

[Greg Amy]

On the VW CIS the "warm up regulator" is properly called the "control pressure regulator". Its purpose is to - duh - regulate the "control pressure," that which opposes the fuel delivery side. By reducing the control pressure you increase the flow of fuel and vice versa... - GA

[evanwebb]

Word Greg. The control pressure regulator isn't magic, its just a fuel pressure regulator that happens to be thermoelectrically controlled, and happens to be regulating the control pressure, not the system pressure.

[kakarot]

It looks like that it would work. On audi/VW system anyways. They have very complicated fuel pressure regulator. Combining both warm up and pressure regulator. They use both intake vacuum, and heated plate to adjust the pressure slightly. While the main pressure regulator is in the A/F regulator it self.

That thing just allows small adjustment for the pressure. It might be enough to adjust the A/F ratio to get proper mix at proper rpm. It is probably easier that to try to calibrate the CIS. However CIS should be properly calibrated and springs used new to get optimal performance and use the pressure regulator to finite adjust the fuel curve.

I hate screwing with CIS I can just make then run properly, never getting any significant performance out of it.

A thing I tried to do is to make a new air box, the box on top of CIS going into the intake. And adding a spring and a screw to adjust the A/F mix. I abandoned that long ago.

[Eric Parham]

The CIS-Lamda guys may be able to use MegaSquirt to control the frequency valve. Remember that the WUR is just a fuel pressure regulator.

http://unwiredtools.com/utcis.asp

To me it looks like an adjustable fuel pressure regulator with a stepper motor.

For A1 and A2 chassis cars:
CIS-Basic 1976.5-1983 (e.g., Rabbit pick-up)
CIS-Lambda 1980.5-1989 (e.g., Rabbit GTI, Golf GL)
CIE-E 1984.5-1989 (e.g., GTI 8V, GLI 1.8L 16V)
CIS-Motronic 1989.5-1992 (e.g., GLI 2L 16V)
Digifant (all types) 1987.5-1992 (e.g., Calif. Golf, Rabbit Cabriolet)

I agree that a MegaSquirt or like system could dynamically adjust mixture on CIS-Lambda by controlling the frequency valve. But, there is a question in my mind about the delayed effect at the injectors. While it might be fast enough to make a difference on a long straight, for example, it seems like it might actually make matters worse in dynamic transitions (unless one were to re-write MegaSquirt as an adaptive control system, probably with learned control parameters for each driver and possibly for each track).

A better choice, if available on the IT model line, would be to control the CIS-E/CIS-Motronic fuel distributor's differential pressure valve, which is faster acting, more accurate, and has a finer control input. With my unfinished ITA Scirocco 16V build, I had hoped to use MegaSquirt&Spark with CIS-E (since I don't think the 16V ever came with Digifant).

Edit: For those unsure if the particular car ever came with CIS-E (or CIS-Lambda, for that matter), don't just assume that it didn't. Check for late-production California cars, Wolfsburg Editions, and possible mid-year switch-overs, especially in the final year of production.