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Originally Posted by AndrewCologne View Post
The only thing is, sometimes after driving when the engine changes to idle, independent from the arduino, the LC-2 sensor controller outputs an error...
Fixed, ... as the control unit from innovate was connected to the relay switching circuit which provided a bit too low voltage/ampere.
Now its connected to where it should be, ... to the same circuit where the eco is connected (->Terminal 87).

Now fine-tuning of the duty cycle regulation/programming is on the to do list for this weekend.
The idle itself ist not oscillating but the sensor voltage reading of the arduino isn't that smooth like in case of a Digi MultiMeter which outputs an almost flat and smooth 2.4-2.5v signal (= 14,7:1 AFR) therefore the sensor voltage output is interpreted incorrectly by the arduino and results in a bit too lean mixture which drops the idle a bit compared to fixed 50% duty cycle resulting mixture/AFR. So the voltage reading paart in the code needs a smoothing/averaging routine ... which I should have taken into account before :-).

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911 SC 3.0, 1982, black, US model

Last edited by AndrewCologne; 09-14-2018 at 03:07 AM..
Old 09-14-2018, 02:05 AM
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Idling fine without oszillating.



Perfectly at stoich around 2.45 volt +/- 0.1v of the sensor ( in case of the LC-2 at factory default 2.45v means 14.7:1)

Now ... when rapidly deacclerating from higher rpms (i.E highway) the idle drops below 700 rpm for about 1 Sec. This was also the case when using the original ECU.
As the Microswitch on the throttle housing tells the ECU when changing from idle to cruise or WOT and ...as well as the change back to idle, I could use this for a proportional enrichening by 1/2 sec when closing the throttle rapidly.

The 30% throttle switch works as expected. I recognised on a highway this 65% duty cycle state pushes the AFR up to between 12.8:1 and 13.4:1
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Last edited by AndrewCologne; 09-14-2018 at 01:11 PM..
Old 09-14-2018, 01:07 PM
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Interesting. Would it be possible to piggyback the arduino w/screen to check for effective ECU operation?
Old 09-14-2018, 02:00 PM
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The whole board with the arduino electronic will be placed in an old original ECU case where the orig board will be removed so from the outer side all will be connected and looking pure OEM like.
The LCD-display could be integrated as panel in the center console, right below the A/C controls.
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Old 09-16-2018, 09:06 AM
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Yeah I guess I was asking if I could replicate your setup condo that test for proper Ecu operation. The box is there, but is it working ? That's the question I wanted to figure out.
Old 09-16-2018, 08:35 PM
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News on this ...

For a prototype with OEM look and OEM connections I took an old CIS ECU Box and removed the old circuit board. The new board came with the needed components and its working flawlessly, means no rewiring etc needed, just plug an play as its OEM like.







The DC regulator is still a stand alone device mounted on the board but will be changed to a solution which is integrated with single elements into the board layout.
The LCD display will be connected later via a disconnectable external plug solution

BTW: With this broadband lambda setup I recognized that when accelerating over 5 sec., the combusition tends to suffer from a too lean mixture!
A fixed factory default 65 % duty cycle should result in at least a 13.5:1 AFR but about 15.5:1 was the reading. So I guess independent from the ECU my CIS maybe suffers from a system or control pressure drop. I'll check that. Would be nice to know if this also happens to other lambda-CIS based engines build in '80-'83. At a first quick view the voltage at the fuel pump is 11v when circuit reaches the pump when key is "ignition on" and about 12v when engine is running, to me this looks ok.
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Last edited by AndrewCologne; 10-01-2018 at 03:01 AM..
Old 10-01-2018, 02:57 AM
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Since 4 weeks testing, optimizing, testing and so on.

Much better and easy duty cycle calculation/behaviour than the original, results in much faster and more precise 14.7:1 AFR output at idle and cruising.
See the voltage reading on the upper left as its kept at stoich (around 2.45 volt).



Narrowband-Output of the LC-2 works perfect as well, means same easy duty cycle behavior and so on like at wideband output. This weekend Ill change the sensor with the real OEM narrowband O2 sensor. Target: Beside the option of working with a wideband sensor controller, also the original sensor setup must be supported by this CPU controlled ECU device.

A big plus of a wideband sensor/controller is also that the pre heating of the cold sensor makes the lambda system initialize/starting much more faster as with the OEM narrowband sensor. About 30 Seconds and the engine will be kept at stoich when engines temp is above 15C.

I also added support of monitoring the engines temperature und the fuel control pressure on the right bottom. The display shows a value of 3.2 control pressure but its actually around 3.4 – will have to optimize the pressure reading in this part of the code.

This CPU controlled setup/version of the ECU shows that a much wieder range of duty cycle values is the result for keeping an optimal AFR during als revs when driving, accelerating.
Example: Engines pressures are ok (System and Control pressure), timing is just 5 advanced as of the premium/Super Plus 98 Octane fuel we have here in germany. SSIs installed.
Basic CO setting is exactly at 0.5%. I added the support of a simple switch where the system is forced to an open loop cycle of 50% and the lower right side of the LCD shows the CO being read from the wideband sensor. This makes it possible to adjust the basic CO much more precise as if using a more spartanic Gunson CO tester or similar.
With this basic setup at idle the calculated duty cycle is at about almost flat keeping 48%. When driving faster (still not accelerating with over 30% throttle ) I realize that the cycle will drop to almost 25%! means without this lambda control the CO would be very hight, even if not needed. When Accelerating the cycle rises immediately to static 65%. With the switch which makes the LCD showing the CO output at such an acceleration the AFR drops to almost 11.5:1 !
12.5 would be here the optimum. This shows me that 65% in some cases would be already too much.

So I did a test and even lowered the basic CO at idle to approx. 0.1%!
This (guess what) rised the duty cycle at idle to about 52% which is logical, resulting idle duty cycle also here still flat and smooth. Now, when accelerating on the highway and the ECU switches to 65% open Loop, the resulted CO is about 12.3 which is almost ideal. This week and with this setting I had the chance to test the cold start at approx 10 C which made the ECU running at initial 65% till the temp rises and make the system go into closed loop. Here with basic 0.1% CO, the car also started up directly and the cold idle was calm and smooth. Till 35C and with sensor still cold/initializing the microswitch makes the cycle rising to 75% for 2 Sec which makes changes from idle to cruising when driving very comfortable – like factory default.

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Last edited by AndrewCologne; 10-17-2018 at 03:55 AM..
Old 10-17-2018, 03:12 AM
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