# Returning to CIS from Megasquirt...help!



## stugatzdub (Sep 3, 2007)

How difficult would it be to return a 90 GLI that has Megasquirt w/spark back to CIS?
What parts would i need? Please, any help would be greatly appreciated. 
Here is a pick of the bay if it helps..



_Modified by stugatzdub at 8:12 PM 9-14-2007_


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## tmechanic (Nov 17, 2004)

*Re: Returning to CIS from Megasquirt...help! (stugatzdub)*

Your MSnS isn't running the spark, your distributor is still handling that.
But your going to need the CIS-e fuel dizzy and all the lines that go with that, the correct CIS injectors, the CIS ECU, the Knock box, if they've deleted that too, the stock fuel pressure regulator. That's off the top of my head, we'd need more pics of what's actually still there, and what's missing.


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## stugatzdub (Sep 3, 2007)

*Re: Returning to CIS from Megasquirt...help! (tmechanic)*

Thanks for the reply. The few changes i know of are..
19lb injectors, Ross Machine fuel rail, Passat TB w/TPS. Here is another bay shot.


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## tmechanic (Nov 17, 2004)

*Re: Returning to CIS from Megasquirt...help! (stugatzdub)*

3OK, I'm a Scirocco guy, so A! chassis only, but after doing some looking you'll need a Digifant system.
Here's a quick run down.
History
Digifant was introduced in 1986 on the 2.1L Vanagon Engine. This system combined digital fuel control as used in the earlier Digi-Jet systems with a new digital ignition system. Digifant as used in Golf and Jetta models simplified several functions and added knock sensor control to the ignition system. Other versions of Digifant appeared on the Fox, Corrado, Eurovan as well as later production versions of the rear engined VW Beetle, sold only in Mexico.
[edit] Features
Fuel injection control is digital electronic. It is based on the measurement engine load (this signal is provided by the Air Flow Sensor), and on engine speed (Signal provided by the hall sender in the distributor). These primary signals are compared to a map, or table of values, stored in the Engine Control Module (ECM) memory.
The amount of fuel is controlled by the injector (duration). This value is taken from a program in the ECM that has 16 points for load and 16 points for speed. These 256 primary values are then modified by coolant temperature, intake air temperature, oxygen content of the exhaust, battery voltage and throttle position to provide 65,000 possible injector duration points.
Digifant is unlike the earlier CIS and CIS-E fuel injection systems that it replaced in that fuel injectors are mounted on a common fuel rail. CIS fuel injection systems used mechanical fuel injectors. The fuel injectors are wired in parallel, and are supplied with Constant System Voltage. The ECM switches the Ground on and off to control duration. All injectors operate at the same time each crankshaft revolution; two complete revolutions being needed for each cylinder to receive the correct amount of fuel for each combustion cycle.
Ignition control is also digital electronic. The sensors that supply the engine load and engine speed signals for injector duration provide information about the basic ignition timing point. The signal sent to the Hall control unit is derived from a program in the ECM that is similar to the injector duration program.
There are 16 points available for load and 16 points for speed. The resulting 256 single operational points are modified by coolant temperature signals and cylinder selective knock control to achieve the optimal ignition point.
Knock control is used to allow the ignition timing to continually approach the point of detonation. This is the point where the engine will produce the most power, as well as the highest efficiency.
Additional functions of the ECM include operation of the fuel pump by closing the Ground for the fuel pump relay, and control of idle speed by a throttle plate bypass valve. The idle air control vale (previously known as an idle air stabilizer valve), receives a changing milliamp signal that varies the strength of an electro-magnet pulling open the bypass valve.
Idle speed stabilization is enhanced by a process known as Idle Speed Control (ISC). This function (previously known as Digital Idle Stabilization), allows the ECM to modify ignition timing at idle to further improve idle quality.
[edit] Inputs/Outputs - Digifant II
The 25 pin electronic control unit used in the Golf and Jetta receives inputs from the following sources:
- Hall Sending Unit (Provides Engine Speed Signal) - Air Flow Sensor (Provides Engine Load Information) - Coolant Temperature Sensor - Intake Air Temperature Sensor - Knock Sensor
Additional signals used as inputs are:
- Air Conditioner (compressor on) - Battery Voltage - Starter Signal
Digifant System Inputs/Outputs
Digifant System Inputs/Outputs
The anti-lock brake system, 3-speed automatic transmission and vehicle speed sensor are not linked to this system.
Outputs controlling engine operation include signals to the following:
- Fuel Injectors - Idle air control valve - Hall Control Unit - Fuel Pump Relay - Oxygen Sensor Heater
[edit] Additional Systems
The evaporative emission system is controlled by a vacuum operated mechanical carbon canister control valve.
Fuel pressure is maintained by a vacuum operated mechanical fuel pressure regulator on the fuel injector rail assembly.
Inputs and outputs are shown in the following illustration. Digifant II as used on Golf and Jetta vehicles provides the basis for this chart.
[edit] System Variants (North America Only)
In North America, Volkswagen released two versions of the Digifant Fuel Injection system. Note that this refers to A2 Golf and Jetta models only.
Digifant I was used exclusively in California market vehicles. Primary differences between Digifant I and Digifant II are as follows:
A limited number of 1987-1990 California Golf and Jetta models are equipped with an On Board Diagnostics system (OBD). These vehicles have blink code capacity to store up to 5 Diagnostic Trouble Codes (DTCs). For the most part, diagnostic troubleshooting is done with a Volkswagen special tool, known as the VAG 1598 and a Digital Multimeter. This system can also have carbon monoxide (CO), ignition timing and idle speed adjusted to baseline values.
In 1991, California Golf, Jetta, Fox, Cabriolet and Corrado vehicles were equipped with expanded OBD capabilities. These later Digifant versions have 38-pin ECMs with Rapid Data Transfer and permanent DTC memory. All Eurovans with Digifant also have rapid data transfer and permanent DTC memory. These systems use a throttle plate potentiometer to track throttle plate position in place of the idle and full throttle switches used on earlier systems.
Another characteristic of Digifant 1 equipped vehicles is a switch mount on the dashboard which has a "Check Engine" symbol.
Summary
Digifant is an engine management system designed originally to take advantage of the first generation of newly developed digital signal processing circuits. Production changes and updates were made to keep the system current with the changing California and federal emissions requirements. Updates were also made to allow integration of other vehicle systems into the scope of engine operation.
Changes in circuit technology, design and processing speed along with evolving emissions standards, resulted in the development of new engine management systems. These new system incorporated adaptive learning, enhanced and expanded diagnostics, and the ability to meet total vehicle emissions standards.
[edit] Maintenance of older Digifant Vehicles
In Volkswagen circles, Digifant has often been criticized for its lack of performance tuning and occasional driveability issues. Most of these issues can be traced back to one of two issues:
- Bad ECM grounds - Faulty Engine Coolant Temperature Sensor (ECT)
The engine coolant temp sensor is located in the coolant flange on the front of the cylinder head.
In the following picture the Digifant Coolant Temperature sensor is clearly visible, as it is identified by a blue electrical connector.
1990 Jetta GL with Digifant Engine Management
1990 Jetta GL with Digifant Engine Management
Common issues that are indicative of a failed ECT are:
- Vehicle idles poorly - Engine sputters, might stall - Higher than normal fuel consumption
The part number for this sensor is 025-906-041-A (Always check with your dealer for the most updated part number).
When replacing this sensor, it is important to also replace the clip that holds it in position (032-121-142) and the O-Ring (N-903-168-02).
Once the new sensor has been installed, start the engine and disconnect the blue coolant temperature sensor. Rev the engine through 3000 RPM 3 times, each time allowing the throttle to close completely. This clears the Digifant ECM fault memory.
[edit] References
Robert Bentley. VW GTI, Golf, Jetta Service Manual 1985 through 1992. Cambridge: Bentley Publishers, 1992.
Volkswagen of America. "Digifant Engine Management." Engine Management Systems. Auburn Hills: Volkswagen Service Publications, 2006. 31-36.
Get a thrashed, rusted out, or totaled Golf GTI or Jetta GLI and start stripping parts.


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## stugatzdub (Sep 3, 2007)

im screwed. 
Thanks for the write-up...very informative.
You need to fly over here to Michigan and use soem of that knowledge on my MS..


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## stugatzdub (Sep 3, 2007)

*Re: (stugatzdub)*

any other info?...parts, difficulty?..


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## PASHAT (Oct 23, 2006)

*Re: (stugatzdub)*

I am going the other way, so I have some info. 
1. You will need to replace your intake system from the air box that used to be there to the throttle body. (This includes the fuel pressure regulator, the DPR, the air flow plate and potentiometer, the fuel lines and the intake boot. If you have a manual transmission, you will have to replace the throttle body and switches.) 
2. You will also have to replace your injectors and your wiring harness and ECU.
3. You will have to take off your fuel rail, your injectors, your MS computer and sell them to me cheap.
4. You should be able to get all of the fuel parts for $50-100.00 at a wrecker.
I would say it will be moderately easy to do. Don't know why Digi was suggested, or why you would want to go back to CIS.


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## stugatzdub (Sep 3, 2007)

*Re: (PASHAT)*

The reason i am not keeping the MS is, when i bought the car it was already on it and i really have no use for it since i am not going to go turbo.
You buy the parts for the swap and the MS is yours.....did i forget to say, "do" the swap..


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## PASHAT (Oct 23, 2006)

*Re: (stugatzdub)*

I would not go back to motronic.... 
MS can be used as a tunable street engine management system....I don't plan to turbo mine either.
But still....sell it to me cheap!


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## stugatzdub (Sep 3, 2007)

back up...list of parts and difficulty level...anyone?


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## PASHAT (Oct 23, 2006)

*Re: (stugatzdub)*

Consider this in terms of spark and fuel.
There are several CIS systems. CIS Basic has no ECU. It has a plate that lifts and controls fuel to lines that end in "injectors".
You could likely simply replace your air intake and injectors and that would work. You would need a temp sensor to power your cold start injector through, but that is pretty easy. However, I don't know if you could provide the fuel and air mixture for a 16v through that system....I believe it was only used in 8vs.
Your distributor would control spark.
CIS-E has an ECU and a knock box. This, to me, would be the most complex to do due to the fact that the knock box and fuel control are separate. Others will know more about that than I.
The third choice is CIS Motronic. You would have to get an ECU, a wirinig harness and then wire up all that is connected to the ECU. It would control both fuel and spark.
I do not see a hall sender on your distributor, so you would likely have to get one that has that. The parts you need would be the inputs to the ECU including knock sensors, throttle swithes, temp sensor, and all the stuff above the air filter including the DPR and Air Flow Pot.


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## PASHAT (Oct 23, 2006)

*Re: (PASHAT)*

If you go motronic, this tells you what motronic needs hooked up to it in order to work..... make sure you have all of the components listed.
http://mysite.verizon.net/macm...c.htm


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## stugatzdub (Sep 3, 2007)

*Re: (PASHAT)*

Thanks for all your help PA. I really appreciate it.
I think im going to take your advice and stick it out w/ the MS. Im going to trace all the wires and see if everything is still connected. Maybe that is why the car won't start...we'll see.


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## PASHAT (Oct 23, 2006)

*Re: (stugatzdub)*

It really wouldn't be too hard to go back, but I am not sure you would gain anything. If you were set on doing so, I would suggest that it would only make sense if you bought a parts car passat cheap....less than 500.00. Scavenge what you need off of it and part the rest out to recover what you paid.
I wasn't aware that your car wouldn't start. However, there are some real knowledgeable guys around here. Post a new question about your megasquirt issue and hopefully someone will help you out. 
Or, I likely have almost all the parts you need.....and would be quite willing to swap you even!








That being said, I can't honestly advise you to dump a system that is working and go to Motronic. Motronic does have a dark side..... I'm not saying it's EVIL, but....


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## Wraith04 (Jun 24, 2004)

*Re: Returning to CIS from Megasquirt...help! (stugatzdub)*

Wow, don't go back to CIS, Megasquirt when tuned properly is great for a daily driver but it does require some homework. Over 6K daily miles on my MS with several trips of 8+ hours and almost 33mpg, something my Digi2 never could have achieved.


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## wclark (Mar 28, 2001)

*Re: Returning to CIS from Megasquirt...help! (stugatzdub)*

If the megasquirt is working, I would not "go back".
For the same or less effort (not to mention the added expense expense) anything not working well could be corrected. 
The engine should run better with a well tuned MS.


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## stugatzdub (Sep 3, 2007)

It's not running. Won't start and when it does start it has a hard time at idle. I just bought the car. I knew of the problems before hand. I don't know much about MS and the info i have read, looks like Chinese. I have been trying to find someone to tune it locally but to no avail...


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## wclark (Mar 28, 2001)

*Re: (stugatzdub)*

OK, that makes more sense.
Either way, you have a BIG project ahead of you.


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## wclark (Mar 28, 2001)

*Re: Returning to CIS from Megasquirt...help! (tmechanic)*

I looked thru my vehicle references and I dont see a Digi II that supported either the 1.8 or 2.0 16V engines. Do you have someting?
I was going to suggest a Digi solution too since the engine is already set up for pulsed injection and going Digi would provide a definite list of the correct sensors and engine mapping (with the right EPROM or ECU). As I couldnt find one, and I assume stugatzdub is trying to simplify this from an engineering design perspective and not make it more complicated, I guessed that is not a good path to take. The first thing I didnt find was an ECU or EEPROM for the Digi II suited to the 2.0 16V. That means a custom EEPROM for a Digi II ECU or standalone engine management, and he is already at the latter with issues.


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## PASHAT (Oct 23, 2006)

*Re: Returning to CIS from Megasquirt...help! (wclark)*

Motronic would be do-able if he could get the components and it would not be too difficult to install. The intake/fuel stuff is all that stuff above the fuel box and would not be too expensive. He could look and see if the ECU is still there. But if he is missing a distributor as well the price of these thiings starts to add up. 
In order to know what has to change, he really needs to make a list of what he has. That being said, there are more people going to MS from Motronic then the way he proposed....likely lots of parts that he needs are available.
If he could get a Passat cheap for a parts car he could take his time and likely have all the parts he needs.
However, MS SHOULD work well. Best choice would likely be to FIX the problem he is having. Having no experience with MS (yet) I cannot help him with this. Perhaps he needs to start a new thread clearly explaining his problems with the car not running?


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## Wraith04 (Jun 24, 2004)

*Re: (stugatzdub)*

Post up your start up maps, VE table and ignition tables. Quite a few people should be able to look at them and see major problems, me included. Maybe start a thread in the SEM forum, most of the MS people are in there, once it is running right with MS you will wonder why you ever considered going back to CIS or Digi.


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## stugatzdub (Sep 3, 2007)

*Re: (Wraith04)*

I will post them up..


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## wclark (Mar 28, 2001)

*Re: Returning to CIS from Megasquirt...help! (PASHAT)*


_Quote, originally posted by *PASHAT* »_Motronic would be do-able 

Yes, if he does elect to go back to CIS, the Motronic solution would be a good one. TT has a chip for it...and the sensor needs are well documented in ETKA.


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## Wraith04 (Jun 24, 2004)

*Re: (stugatzdub)*

Link to my current MSQ. easier to load then typing in all the constants.
This is on an ABA crossflow, 270 cam, 24lb injectors, using an LC-1 WB.
http://www.msruns.com/download.php?id=5676


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## kd7jkr (Feb 27, 2007)

*Re: (Wraith04)*

considering you are going back to CIS, what are you going to do with the Megasquirt stuff, i am very interested in all of it, any thoughts


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## PASHAT (Oct 23, 2006)

*Re: (PASHAT)*


_Quote, originally posted by *PASHAT* »_
3. You will have to take off your fuel rail, your injectors, your MS computer and sell them to me cheap.


Butt out buddy!








I got FIRST DIBS on it....!








Besides, I think he has realized that it is easier to fix what he has, then transfer everything back to CIS and have to fix that....


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## stugatzdub (Sep 3, 2007)

*Re: (PASHAT)*

lol...Pa is right...and if i do go back he has first dibs.


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