Using MS to control CIS/K-Jetronic FI systems

[T3Bunny]

As for controlling CIS without the plate. You can simply use a MAF sensor in place of the plate. However, you still need some way of controlling the plunger through it's whole range of movement, which leads you straight to needing a fast, accurate servo with the appropriate stroke, which costs big money..

Okay, a few holes here. And the WHOLE point of my idea is being missed. First WHY use a MAF sensor? Use a standard MAP like in the MS. A MAF is going to be a pain to install and be obvios, pluss its still a restriction.

Second, rip out the plunger and forget about the servo. They are not needed. What you would do is simply use the fuel distributer as bascialy a fuel manifold. Have it fed by ONE solenoid that you PWM like a standard fuel injector. If your going to retain the CIS system for the stealth look or for the atomization of the injectors, then retain it. Simplify it. Why make it hard with control algorythums when everything you need is already there?! Just use a solenoid to modulate the feed pressure.

Granted, this is all theoretical. BUT, I would spend the 30-50 for experimenting with a valbe, that can be made to work without code changes, or makeing compleatly new code, and all that. As opposed to a system that does NOTHING too simplify or address the issues of the CIS.

Take tha advantages of both systems, and combine them. GET RID of the disadvantages of the CIS. Mainly its SUPER restrictive airplate. TOSS IT OUT! Use the better atomizing CIS injectors. If the concept above still isn't making sense, take a look at the Aquamist Water Injection systems with multiple jets and PWM injection contol. Its super simple and can likely be applied to this concept. The only tricky issue I see is matching the flowrate of the solenoid used for fine idle control. One might have to use two solenoids and say the Roger Enns staging control to use a smaller solenoid for idle.

As for the pop off of the CIS injectors, I don't know if Benz runs theirs higher, bu the Bosch injection manual says between 45 and 50 psi is the pop off. And I have found that they will frequantly pop off and start spraying as low as 35psi.

IF, and this is a BIG if, somebody were to go through the trouble of doing this weird conversion.... Keep it simple. Forget about expensive servos and components controlling a bad setup. Get rid of stuff like that. Keep it looking as stock as possible... Get the MS to do what it already can do. PWM control solenoids. Sure tuning will be entertaining until you get the hang of things. But the headaches for trying to create new code for a servo won't be there.

I can't think of any reasons anyone would want to retain the look of a CIS system though

[chois]

I appreciate what you are saying, and agree that the air flow plate is a restriction. This is why I am putting MS on my CIS-E Motronic 16 valve.

However I have another application that I would like create a 'programmable' CIS-E system, maintaining the airflow plate. It is for a competition engine that must retain 'CIS type' injection. If we can simply have discrete control of the fuel it will help a lot, we are not airflow limited at the plate on this application as it is a small engine. Is there anyone that can help me with this, or anyone you would recommend I approach?

thanks,

[T3Bunny]

Do a little research, and also look up Peter Tong on the VW vortex. I know he is running some sort of fully programable setup on his own CIS car.

And I would still use a MS to control the spark. Its deffinatly a possibility to still use the MS to control a later motronic style regulator, I am not sure what it would involve though.

[chois]

No surprise that Peter Tong came up, he really seems to have a soft spot for CIS sysetms. If anyone stumbles across this thread and thinks they can help me generate a 0-20mA signal to feed the DPR based on VE table location, please contact me.

Just to be clear on my 16v there is no way I am leaving the CIS fuel delivery hardware in place. It will be a 'typical' Megasquirt conversion.

[R2.0]

A tangential comment...

With CIS, you can't really control the amount of fuel going into individual cylinders. Doesn't that somewhat defeat purpose of EFI?

That's not exactly true. On some (most?) CIS fuel distributors there is a trim screw that will adjust pressure for each injector. Theoretically, they are used with EGT probes (or, for air cooled, CHT sensors), to trim individial cylinders. But it isn't dynamic, and from all reports one can seriously screw up your system bymessing with these arbitrarily.

R2.0

[R2.0]

As for controlling CIS without the plate. You can simply use a MAF sensor in place of the plate. However, you still need some way of controlling the plunger through it's whole range of movement, which leads you straight to needing a fast, accurate servo with the appropriate stroke, which costs big money..

Second, rip out the plunger and forget about the servo. They are not needed. What you would do is simply use the fuel distributer as bascialy a fuel manifold. Have it fed by ONE solenoid that you PWM like a standard fuel injector. If your going to retain the CIS system for the stealth look or for the atomization of the injectors, then retain it. Simplify it. Why make it hard with control algorythums when everything you need is already there?! Just use a solenoid to modulate the feed pressure.

A couple of things. First, I don't think a servo is the answer either. On Cis-E, the plunger is controlled by the frequency valve, which looks and acts suspiciously like a regular Bosch injector. So I think its' possible to use MS and a frequency valve or injector to do full range fuel control.

Second, the idea of using one big fat injector to feed the CIS distributor is intrigueing. 3 questions:

1) Flow - That's a pretty damned big injector. Adapt a Ford CFI?
2) Pressure Pulsations - at low flow, the injector will be off most of the time, so we are losing the advantages of the "continuous" aspect of CIS.
3) Total Pressure - While CIS injectors pop at pressures in the normal operating range of a CFI injector (I think), they don't necessarily like to *operate* at those pressure. How will a CFI injector take to operating at standard CIS pressures.

One solution would be to use 2 or 4 smaller injectors manifolded together, and use both banks alternating to trigger them. This would smooth out the pulses, and maybe alowa wider injector selection?

R2.0

[T3Bunny]

A couple of things. First, I don't think a servo is the answer either. On Cis-E, the plunger is controlled by the frequency valve, which looks and acts suspiciously like a regular Bosch injector. So I think its' possible to use MS and a frequency valve or injector to do full range fuel control.

A servo is definatly not the way. It would be expensive to impliment and it would likely require special coding.

Lemme address your second question first. Mainly we are dealing with very light throttle and idle at these flow rates. I am not sure that its going to matter much here. I feel its a non issue. No matter what system you go with there will probally be a bad point or comprimise.

Questions 1 and 3 are assuming a familiarity with the ford injector. And are realy directed at that. I posted a cool link on the first page: http://www.stcvalve.com/I-Solenoid.htm#0 I think that one or two of these might have the flow capability needed.

As for the low load situation, I can see something like an accumalator being used between the solenoids and vlaves. The real idea though, would be a setup that allows relitivly cheap experimentation to occur.

And it would be super cool, to try and simply impliment an existing setup using either the frequancy valve ot the electro hydrolic actuator used on the more modern Motrinic CIS rigs. That would actualy have broad appeal to the VW croud.

[R2.0]

Questions 1 and 3 are assuming a familiarity with the ford injector.

Sorry - the Ford CFI injectors are basically (very) large Bosch style injectors with different ends - they can flow upwards of 50#/hr a piece. And they can be modified to standard ends.

And it would be super cool, to try and simply impliment an existing setup using either the frequancy valve ot the electro hydrolic actuator used on the more modern Motrinic CIS rigs. That would actualy have broad appeal to the VW croud.

That's kind of what I was getting at in my first 2 posts My problem is lack of time and a proper CIS setup for experimentation. That's why I was more throwing it out there as an idea.

[lapuwali]

I love this. Multiple injectors to control the pressure? Why not just move those injectors to the ports and forget the CIS fuel distributor altogether?! CIS is one of the simplest FI systems available, and you guys are dreaming up all kinds of ways to make it very complex. Trying to control the entire system pressure with one injector would be very challenging.

The only reason CIS atomizes better than EFI is the higher system pressure. I have no idea where T3 gets his data, but the Bosch books all speak of 100psi system pressures, not 50 or even lower.

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.

MAF sensors don't have to be restrictive. There are 400hp OEM cars out there with MAF sensors. Just use one that's big enough and there won't be any restriction.

[T3Bunny]

What is the point of running the MAF? It adds to the cost, and there is a nice MAP sensor in the MS already. The point here would be to retain the STOCK apperance of the CIS system and to gain some further measure of control over it. Also to try and maintain the charachteristics of the fuel atomization that the CIS system has.

Anyone familiar with the water injection systems by Aquamist, will understand what the thought here is. Not using the injector to control fuel pressure exactly, but to control the flow. Of course in a CIS system they basically become the same thing.

And the other point, was to fully retain the CIS setup and use the MS to control it VIA a frequancy valve or the hydrolic actuator.

Whatever the case, this is a theoretical discussion still. As nobody here realy intends on running this, yet.