O2 sensor delete - how to do it?
12-25-2005, 10:27 PM
#16
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The altitude compensator is a switch that is open below 1000 metters and closes above 1000 meters. It decreases the fuel mixture if the switch is closed (above 1000 meters). On the 87 Turbo schematic, it states US only.
Most of my experience has been with the Turbo, I looked up the Coding plugs for the 944S and 944S2 and they are different. If you have the manuals, they are listed on page 24/28 -31 of Volume 1-A. Here is the scan of the two pages for the code plugs. Also there is a scan of the electrical schematic for the 87 944S showing the code plug connections. If I am reading this right, you should have a code switch 2 that is open unless you have a USA Ca car, then pins 1 and 2 are connected with a plug. To switch to ROW, connect pin 1 to pin 3.
Coding Switch 2
Pin 1 connects to 12VDC power.
Pin 2 goes to the DME Pin 39.
Pin 3 connects to ground.
Good luck.
Most of my experience has been with the Turbo, I looked up the Coding plugs for the 944S and 944S2 and they are different. If you have the manuals, they are listed on page 24/28 -31 of Volume 1-A. Here is the scan of the two pages for the code plugs. Also there is a scan of the electrical schematic for the 87 944S showing the code plug connections. If I am reading this right, you should have a code switch 2 that is open unless you have a USA Ca car, then pins 1 and 2 are connected with a plug. To switch to ROW, connect pin 1 to pin 3.
Coding Switch 2
Pin 1 connects to 12VDC power.
Pin 2 goes to the DME Pin 39.
Pin 3 connects to ground.
Good luck.
Last edited by Bri Bro; 12-25-2005 at 10:42 PM.
03-31-2018, 03:23 PM
#17
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I realize this is an old thread but I'm rebuilding a 97 944s and wanted to verify the correct ROW pin bridge....
From the picture above, corresponding to the 944s it appears that you should "bridge to ground" for ROW, corresponding to pin 2 to 3. The associated example depictions in the upper left of the pic seems to suggest this as well (there is NO depiction of jumping pin 1 to 3). I'm assuming 'ECE' is the same as ROW in the pic.
To me this seems logical since you I would think you are trying to send a signal to the DME (pin 2 on the jumper goes to DME pin 39) although I guess the DME could see this in a non-direct way.
I'm hesitant to connect pin 1 to 3 , as suggested, since it is 12V to ground and I'm concerned it could fry something, if wrong
can anyone clear this up?
Thanks!
From the picture above, corresponding to the 944s it appears that you should "bridge to ground" for ROW, corresponding to pin 2 to 3. The associated example depictions in the upper left of the pic seems to suggest this as well (there is NO depiction of jumping pin 1 to 3). I'm assuming 'ECE' is the same as ROW in the pic.
To me this seems logical since you I would think you are trying to send a signal to the DME (pin 2 on the jumper goes to DME pin 39) although I guess the DME could see this in a non-direct way.
I'm hesitant to connect pin 1 to 3 , as suggested, since it is 12V to ground and I'm concerned it could fry something, if wrong
can anyone clear this up?
Thanks!
03-31-2018, 09:37 PM
#18
Burning Brakes
Wow - 15 years on this one! 
FR Wilke's site is long gone, but fortunately you can't erase the internet! https://web.archive.org/web/20120415...ww.the944.com/
Ok, my 944 NA is gone along with most of my manuals, however if you dig back into the site I linked above, you will find:
To the best of my recollection, the 944S DME is similar in coding to the NA. If the logic above is correct, then all you need to would be to run on the non-US mapping (full power) is to unplug the oxygen sensor. This will bring Lambda to 0 (or infinite) and the computer will default to the power map. The lambda values in this case would be out of the range that the DME would try to adjust, so the computer not make any effort to pull fuel to lean out the mixture = full power. No need to change maps I think. Read through the site as it's a fun read anyway, but I think there is enough information in there to back up my hypothesis. Good luck with it!
FR Wilke's site is long gone, but fortunately you can't erase the internet! https://web.archive.org/web/20120415...ww.the944.com/
Ok, my 944 NA is gone along with most of my manuals, however if you dig back into the site I linked above, you will find:
The basis ML1.1 system, the early Euro 944, has no Lambda system. The air flow sensor and speed sensor are used to determine fuel flow from a map that is stored in system memory.
Next to it is the ML1.2 Lambda system flow chart, the early USA 944, which has a Lambda sensor (O2 sensor). The fuel level is a two level control process, map and Lambda control. The Lambda system also uses the air flow sensor and speed sensor to determine fuel flow from a map. The Lambda control makes positive or negative changes to the fuel level in order to fine tune the fuel output. The range of the Lambda control is quite limited which requires the fuel map to contain values very close to Lambda=1 (air/fuel ratio 14.7). Comparing the maps of a non-Lambda (Euro 944) and Lambda system, the Lambda maps will appear flat and unimpressive. The power is in the non-Lambda map.
The fuel map is always used with a Lambda system. One common but false saying is that the fuel map is no longer used when the car is equipped with an Lambda sensor. This is far from the truth. Where does the original fuel value come from? Is it a guess? No. Any change in load or engine rpm, the DME must go to the fuel map to get its initial value. Then the fine tuning begins. The Lambda sensor subroutines take charge and the fuel is continuously toggled back and forth. If the Lambda sensor is disconnected, the Motronic gets it fuel levels from the map only. It never just "goes rich to protect the engine" which is another famous and incorrect saying. When the Lambda is disconnected, it uses the fuel map.
For simplicity sake, the contribution of temperature has been omitted from the discussion. Fuel atomizes poorly at low temperatures requiring some mixture enrichment.
Next to it is the ML1.2 Lambda system flow chart, the early USA 944, which has a Lambda sensor (O2 sensor). The fuel level is a two level control process, map and Lambda control. The Lambda system also uses the air flow sensor and speed sensor to determine fuel flow from a map. The Lambda control makes positive or negative changes to the fuel level in order to fine tune the fuel output. The range of the Lambda control is quite limited which requires the fuel map to contain values very close to Lambda=1 (air/fuel ratio 14.7). Comparing the maps of a non-Lambda (Euro 944) and Lambda system, the Lambda maps will appear flat and unimpressive. The power is in the non-Lambda map.
The fuel map is always used with a Lambda system. One common but false saying is that the fuel map is no longer used when the car is equipped with an Lambda sensor. This is far from the truth. Where does the original fuel value come from? Is it a guess? No. Any change in load or engine rpm, the DME must go to the fuel map to get its initial value. Then the fine tuning begins. The Lambda sensor subroutines take charge and the fuel is continuously toggled back and forth. If the Lambda sensor is disconnected, the Motronic gets it fuel levels from the map only. It never just "goes rich to protect the engine" which is another famous and incorrect saying. When the Lambda is disconnected, it uses the fuel map.
For simplicity sake, the contribution of temperature has been omitted from the discussion. Fuel atomizes poorly at low temperatures requiring some mixture enrichment.
