[tkacki]

Hmn....How did You switch between maps if the information about variant coding is so new to You ?



Diagram: wiring page 97-11, "Engine compartment, cruise control", location: A50.

CO adjustement: Volume I, "Fuel System - Electronic Injection", page 24-2.



In M150 mode You will achieve full power without cat and lambda.



The main power loss reason in this Motronic implementation (968) is the air intake temp measurement. This car has no air intake temp sensor. s*** ! The IAT sensor in MAF is not used ! The sensor line of the DME (a/d input) is used for oil temp sensor (DME needs to know oil viscosity to adjust vario cam swich timing). Inlet air temperature is calculated on the fly based of MAF reading. Yes, they use standard motronic box to implement vario cam. Result: in full throtle mode, when DME is using 2D maps: engine rev speed - > fulel, engine rev speed - > ign advance, the correction for air temp is based on "virtual" temperature value.



This saving (f***ing single pin) costed a lot ! Beacuse of this, the car is slower and slower day by day after it leaves the factory as MAF decalibrates with age (MAF is the only device sensitive to inlet air temp). Try new MAF (costly :/) and You will find the difference. Porsche did this only in 968, 993 with similar motronic conf. measures the inlet air temp.

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[flash]

thanks - found it - now i know why i couldn't find it before - it was tucked away down in the corner of one page and no real indication that it was significant - good find



"variant coding" isn't new to me, but the idea of inserting a resistor into the wiring to achieve a bypass was new information - still not sure it's the right answer for me, and is probably exactly the opposite direction i need to go, but it is interesting, and it may come in handy on other mods



as for how i changed maps, there was no need to mess with wiring diagrams or anything to change maps - the mapping is done in the chip, so it was simple - pull a chip - wait required amount of time to reset - insert a chip - bingo - map switched



i just wish there were more data points down low, and at part throttle so as to be able to clean up the mixture more for the dyno emissions testing



but once i put the factory cat back in there, i will have cleaned it up AND gained more torque

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[tkacki]

Yes, the mapping is in the chip. Chip = program and data memory. To change maps You have to pull out the chip, then reprogram. Howewer every chip stores 3 sets of maps, so You can modify specific set, program the chip, inster into DME, and then - change between sets during the driving as You wish.



Try experiment: Mount a switch and 1k resistor in serial configuration and insert it into the plug near DME. Try to drive and swich during driving. You will fell the difference. I can prepare a schematic for You, if You like.

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[flash]

that would be cool, yes - always up for a new test



as i said, i think i am already running too rich at the levels being tested, so this probably won't help my specific problem, but it could be interesting in some other areas i have been looking to play with

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[Roboman]

M150 is no cat option. PET says: M150 - operates with leeded gas. It is: no cat, no lambda, fixed maps. Every ecu has fixed maps.

To convert You need 10k potentiometer and 1k configuration resistor.



You can also convert Your 968 to "original factory" M150 using folowing parts:



1. Confuguration adapter / plug 944 612 492 00 - which is simple 1k resistor as mentioned, to be inserted near DME.

2. CO potentiometer 944 606 212 00. Originally it is located near ignition coil.

3. Cable / harness (between pot and lambda socket) 944 607 175 00.

4. Support 944 606 053 01 - to mount potentiometer.

5. Screw / cap 900 219 015 00 - to fill the hole afer lambda removal.

6. some minor hw (bolts, washers).

 

Boy am I happy to have found this post .... tkacki if you are still around, many thanks!!!

 

My car was exported directly to the Sultanate of Oman with the 150 option, which I understood was for countries with leaded petrol but I didn't know exactly what that meant ..... now I realise why I have an mixture adjustment pot (Bosch 0-280-101-013) near the right side headlight which is connected to the socket where the lambda should be.  And of course no lambda ..... but I do have a cat, which is slightly confusing ..... 

 

Here's the pot at the front of the car ...

     

 

 

Which explains the two pin going into three pin where the lambda should connect.

     

   

 

My car has just failed the emissions test, and seeing the lack of a lambda sensor I thought installing one might help, but I was thrown when I saw this unknown pot connected at the "lambda to ECU" junction. 

Now it is all clear and I have only one difficulty ...."To switch the DME You should put 1k resistor in 3 pin sockect near DME plug."

 

Removing the 1K resistor .....GUIDANCE /PHOTO WOULD BE APPRECIATED ...

 

I have posted this to help others in the future who may be likewise mystified by the 150 option and a pot instead of lambda.  I'll update this post when I have more information.

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[Waylander]

Your tester guy should be able to trim the emissions with the pot at test time, and when was the last time it had a proper Italian tune up?

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[Roboman]

Unfortunately with the French system the vehicle test stations carry no tools and cannot work on a car.  The testing system is remote from the garage/workshop system in order to remove, I guess, conflict of interest/bribery/etc.

Italian tune-up ??  Ha ha, yes it's been a while, food for thought .....

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[Roboman]

I doubt this concerns anyone at the moment but it may be a solution for other problems .... 

 

The local garage managed to remove the "Screw / cap 900 219 015 00 - to fill the hole after lambda removal" by alternating induction heating and freezing. 

 

They have a small induction heater, the coil of which would be just large enough to pass a good sized sausage through (perfect bar-b-q but only one sausage at a time) so they heated the bung for a while and then sprayed it with freezer solution.  Did that twice and suddenly "snap" and the bung twisted out.  Given that bung has been in place for 30 years I was impressed.  I also thought it might be an interesting approach for loosening other stubborn parts.

 

The oxy sendor is in, so now I need to find the 1K resister before testing again this afternoon.  Wish me luck .....

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[Roboman]

Found 944-612-492-00 1K resistor plugged into the DME (top of photo, white plug with orange label).  Usual process to get there: rip up passenger carpets, ease out DME holder, remove Porsche "goop" from my hands/tools/etc. 

 

Here it is, a plug/socket arrangement with a 1K resistor soldered in line to activate a standard map.

 

   

 

Firstly I used my Durametric with the 1K in place, then removed the 1K and restarted the car  ......

 

   

 

Top line is the Oxy sensor with the lambda-delete pot in place ..... flat line as expected

Next line is immediately after removing the 1K and attaching the lambda ... some lambda response, but mainly still around 1.0

Middle graph is after a few minutes of using the lambda, the real time responses are kicking in .... response centred around 0.9

Next to bottom is at idle and the sendor is oscillating around 8.4

And finally the bottom graph is where I take my foot off the accelerator (around 4Krpm) and the sensor tracks from 1.0 down to idle around 8.4 again.

 

So things appear to be responding/working, now I just need to pass the emissions test  :whine:

 

I found my way through this maze as a result of a post from some 16 years back, so I hope my additional details may serve as use to someone in the future ..... as a matter of interest I've read a few posts on other sites, eg Porsche GB and others, not much knowledge out there .....

 

 

 

 

 

 

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[Roboman]

The news is good ..... thanks to all who had their fingers crossed.  The CO limit here in France is less than or equal to 3.5%, here's my results over consecutive tests ....

 

2016 = 2.99%

2018 = 2.90%

2020 = 2.65% (I was recommended a hydrogen wash before taking this test)

2022 = 3.42% (did hydrogen wash but it's getting close)

2024 = 6.10% (did I get ripped off by the hydro-wash man??) Anyway, needed to do something ....

2024 = 1.07% The only change was removing the pot, remapping by removing the resistor, and inserting the oxygen sensor.

 

The engine now seems slightly smoother, but also needs my foot on the accelerator for a couple of seconds at first start in the morning, else it dies if I immediately take my foot off the gas. Previously it would run up at first turnover without my foot on the pedal at all, and keep running.  I guess the pot was set a little rich and, as Waylander said, could have been adjusted by someone competent (Martin, you weren't having a go at me were you?     )

 

Anyway, all good now  :clap:  :clap:  :clap:

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[unknown4u]

Sounds to me like a faulty dme, because it supplies a 12 volt+ to the idlespeed.stabilizer.



The dme, because it is worn out, still gives the petrolpump 12volts, but no longer a 12 volt to the stabiliser.

Thats why it stalls at the start up

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[Roboman]

Okay, thanks for that, but I think I'll leave it alone.  It runs okay after that initial blip on the accelerator ...... of course things might be different in Winter.  Anyway, thanks for your note

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[Waylander]

The O2 sensor does not start affecting the running till the blue temp sensor and the oil temp sensor tells the ECU the engine is ready

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[Waylander]

The news is good ..... thanks to all who had their fingers crossed.  The CO limit here in France is less than or equal to 3.5%, here's my results over consecutive tests ....

 

2016 = 2.99%

2018 = 2.90%

2020 = 2.65% (I was recommended a hydrogen wash before taking this test)

2022 = 3.42% (did hydrogen wash but it's getting close)

2024 = 6.10% (did I get ripped off by the hydro-wash man??) Anyway, needed to do something ....

2024 = 1.07% The only change was removing the pot, remapping by removing the resistor, and inserting the oxygen sensor.

 

The engine now seems slightly smoother, but also needs my foot on the accelerator for a couple of seconds at first start in the morning, else it dies if I immediately take my foot off the gas. Previously it would run up at first turnover without my foot on the pedal at all, and keep running.  I guess the pot was set a little rich and, as Waylander said, could have been adjusted by someone competent (Martin, you weren't having a go at me were you?     )

 

Anyway, all good now  :clap:  :clap:  :clap:

Absolutely not, I never have a go at anyone

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[Roboman]

The O2 sensor does not start affecting the running till the blue temp sensor and the oil temp sensor tells the ECU the engine is ready

Thanks for that ..... and of course I didn't think you were having a go, not your style  

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