MicroSquirt.com read only forum (Jan.15,2018)

lapuwali wrote:
The plunger is NOT directly controlled by the PWM valve on CIS-E. The only thing that's attached to the plunger is the airflow plate. The PWM valve alters the control pressure, which alters the air/fuel curve by altering the resistance to movement of the plunger by the airflow plate. Controlling this valve IS the way to control fuel flow while retaining the airflow plate (which a previous poster listed as a goal). This would not be at all hard to do.

Actually, that's not quite the case, but it is what I WANT to do.

On CIS-Lambda, the lambda valve/pwm valve trims mixture by manipulating pressures within the chambers in the fuel distributor (just found my Probst book). What I want to do is replace the Control pressure regulator with a PWM valve.

On a CIS system, injector flow is a funtion of the position of the plunger. Gross position determined by airflow, with the force of the airflow on the meter plate counterbalanced by the control pressure on the other side of the plunger.
Reduce control pressure:
- counterbalance force on the plunger is reduced
- resisting force on the plate is reduced
- the arm moves
- plunger moves
- equilibrium reestablished.

Now, what if we replaced the air flow plate and arm assembly with an appropriate sized spring? Size would be such that, at highest control pressure, spring is fully compressed, plunger is at it's bottom stop, and flow is minimum.
Now, as control pressure is decreased
- the spring expands
- the plunger moves up
- flow increases.
How do we make the control pressure fall? By increasing the frequency valve duty cycle. The MS should use a similar fuel map driving the frequency valve as driving standard injectors - as load goes up, valve opening time goes up.

What I'm proposing is different from T3 and chois. Where chois proposes keeping the appearance, it is the appearance that I specifically want to alter. I want to get the advantages of CIS in a smaller package with more mounting options. That means ditching the air flow meter.

R2.0

The advantages of the CIS will not be enough to outweigh the difficulty of making it and testing it and all that.

My idea does not need ANY of the fuel distributer to work. I just maentioned using it because there realy is only a few reasons to retain the CIS when all is said and done. Even with the few disadvantages of the EFI injectors, there are MANY more advantages to using them.

But back on track, your spring idea could be simplified I think. All you need is a thick plate with a hole drilled most of the way through in the center. Set it up so a spring sits in the hole and pushes against the plunger. Now how well will it work? Hard to say as there is a lot of force acting on the airplate when its being used. Your going to need some reliable springs, and a bunch of differant weights on them.

I figure this is all I really need to make this work. I just don't have the skills to do it. Any computer engineer types feel generous with their knowledge right now?

I gave this a shot on my old CIS-Lambda Rabbit about 2, maybe even three years ago.

I ended up using dual table code to get rid of the enrichments, then went through with the stim and a mity-vac to EVERY load bin to get the calculated duty cycle to 50% (just like a normal cis-l car) with the O2 locked at .5v. It ran and drove but I didn't have a wideband at the time so I really couldn't tune it at all. Performed just as well as the stock stuff at part throttle but was lean up top, or sounded like it.

I'm also not sure if the lambda valve will like the varying frequency over the long haul. Oh, and be sure to run a V3 or the flyback board the lambda valve is very low impedance.

You have CIS on the car, and then want to add a MS due to not enough space.
Won't that take up more space than just a MS?
With the ms you have the ecu (in car), fuel rail and some sensors, thats not the same amount of space the whole CIS system requires...
I think the setup with flow meter and valve will work, getting rid of the air flow meter won't work <- Mechanical injection

Actually I think it could work if the flow meter was locked at its highest position and the lamda valve was used for total fueling control. Of course MS isn't really set up to handle this, and is assuming that the lamda valve has enough pull to vary the system pressure enough to get the car lean enough with the meter at full tilt.

It just seems that processing a duty cycle signal to a 0-X current signal would be pretty easy for any electrical engineering student out there. Too bad I was never one of those...

I would look at the system used by GM on the Vortec Central fuel injection systems. it has one large injector and distributes the fuel through plastic tubes to multiple injection points. the large injector is pulsed but feeds all the ports at the same time. a similar technique could be used.
I hope this helps
Brian

What about removing the airbox and fuel distributor altogether. Connect each CIS injector line to something like an injector valve but without the spray component. Add a TPS to the stock throttle body. I am thinking back on my 82 Scirocco, which is long gone, so I may be missing something. Anyway, the MS would become the fuel distributor, firing valves to open the fuel to each injector. Of course, it wouldn't be CIS anymore. I remember being blown away by that stock setup of air before fuel - wacky. At one point I added a full throttle encrichment switch which altered the PWM on the fpr. Some of the later cars had these built in of course.