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AndrewCologne AndrewCologne is offline
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Join Date: Aug 2015
Location: Cologne / Germany
Posts: 227
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.
911 SC 3.0, 1982, black, US model
Own digital ECO build
All about the 930/16 and 930/07 Lamba based US SC models:
(its in german english will follow, use google translator meanwhile)

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