Motronic 35 Pin to 55 Pin Adapter

[02rollin]

Hey all,


This idea stemmed from a discussion on mye28.com, some of you don't frequent that forum so I am posting here. I come from the e30 world and was turned on to the shortcomings of Motronic 1.0 when i bought a euro 325iX that ran Motronic 1.0 and a 073 ECU (35 pin). I started modifications and learned it did not come with all of the sensors necessary to upgrade to the later Motronic 1.3 in order to run a 55 pin ECU and/or a Megasquirt unit built into a 55 pin board.


I ultimately performed an engine harness upgrade and supporting sensor upgrade to make my car run the 55 pin M1.3 and Megasquirt for forced induction. I was and still am surprised nobody has made an adapter for the 35 pin ECU's to the 55 pin so they could plug and play a 179 or similar ECU (megasquirt). I also learned at that time that the M20b27 (325e/s,528e) uses the 35 pin board and is the basis for the 2.7i stroker engines that is common in e30 circles. Why not have the ability to fully tune spark and fueling without having to change engine wiring harnesses or buy multiple pricey EPROM chips?


So I decided to look into the adapter and found the correct 35 pin male connector that allows this possible and am currently waiting on the 55 pin connector to see if this will work. Assuming I found the correct adapter, the next step would be wiring the circuit up correctly and building a prototype to test. Also something to note is the db37 cable is not needed with this setup so the unit does not have unnecessary cables and should be able to fit in the factory space. Here is a simple graphic to show you how it would work.





In case you are unfamilar with Megasquirt, here is the DIYPnP 55 pin kit that you can buy unassembled, or you can buy prebuilt running the Microsquirt module and MS2/E v3.0.3 or later.
https://www.diyautotune.com/product/...assembled-kit/





Some features of megasquirt if you are unfamiliar:
Speed Density, Alpha-N and Hybrid Alpha-N (both SD and A-N algorithms hybridized) Supported
Onboard 2.5 bar MAP sensor
2 Ignition Inputs (for dual wheel ignitions)
4 Spark Outputs (Up to 4 Cylinder Coil On Plug, up to 8 Cylinder Wasted Spark)
Natively support two fuel outputs for batch or bank-to-bank fueling. Optionally upgrade to 4cyl sequential or 6/8 cyl semi-sequential with this module.
Enhanced Acceleration Enrichment (EAE)
Boost Control
Knock Control
Launch Control
Flat Shift
Tachometer Output
Fully Adjustable Rev Limiter
Table Switching
4 General Purpose Outputs
4 General Purpose Inputs (2 analog, 2 digital)
Support for Flex Fuel
Optional Realtime Baro Correction
Closed Loop O2 Correction
Plenty of Proto Area, add your own customizations!


Some other suppliers of 55 pin Megqsquirt units include Sssquid Tuning (http://sssquid.com/v2/shop/tunes/bmw/megasssquirt/), Whodwho's 55 pin unit on R3vlimited.com (http://www.r3vlimited.com/board/showthread.php?t=202653), Dedericms.com (his site is down now though)


What will you need to fit megasquirt to your e28?
- Variable TPS off of an e34 automatic, or variable TPS from an e36 with adapter bracket (I found a supplier and maybe able to provide these also)
*Note one wire usually needs to be swapped to make this TPS work, so I am looking into a TPS to vTPS adapter as well)
- 60-2 toothed wheel/harmonic balancer and CPS/bracket from e34
- Intake Air temp sensor (GM, or the sensor in the factory AFM unit)
- Vacuum line to the ECU
- 55 Pin ECU (Megasquirt or BMW ECU)
- High Impedence Fuel Injectors (or i read low impedence injectors could possibly be used with certain megasquirt settings)
- 55 pin engine Wiring Harness OR this 35 pin adapter
- (Not necessary but a wideband oxygen sensor like the AEM UEGO or Innovate LC-1 is recommended.)


What cars will this theoretically* work on?
*this assumes the pinout will work and I have not yet verified all of the models listed below are 35 pin, but it should include m30b35 models through mid 1987 with the 35 pin ECU connector. This also assumes you can find a 60-2 CPS wheel/sensor which is available for the e23/e24/e28/e30. I believe you can use an m30b35 cps/wheel on the s38 and/or s38b36 cps/wheel on the s38b35 but i am not aware of an option for the s14. The m42 could possibly fit but I have not heard of anybody trying it yet.

325e/es
E30
M20/B27 (122hp)
9/84-12/86
0 261 200 027
Bosch Motronic Basic M1.0


325i/ECE
E30
M20/B25 (171hp)
85-87
0 261 200 081
Bosch Motronic M1.0


M3
E30
S14/B23 (195hp)
86-08/89
0 261 200 071
Bosch Motronic M1.0 Motorsport


M3
E30
S14/B23 (215hp)
09/89-90
0 261 200 091
Bosch Motronic M1.0 Motorsport


M3 - Evo2
E30
S14/B23 (220hp)
88
0 261 200 090
Bosch Motronic M1.0 Motorsport


M3 - Evo3
E30
S14/B25 (238hp)
01/90-05/90
0 261 200 092
Bosch Motronic M1.0 Motorsport


533i
E28
M30/B32
84
0 261 200 008
Bosch Motronic M1.0 Basic


528e
E28
M20/B27
9/84-12/86
0 261 200 027
Bosch Motronic M1.0 Basic


535i/is
E28
M30/B34
85-87
0 261 200 059
Bosch Motronic M1.0 Adaptive (24 pin)


535i/is
E28
M30/B34
88
0 261 200 059
Bosch Motronic M1.0 Adaptive (28 pin)


535i/is
E28
M30/B34 (218hp)
85-87
0 261 200 061
Bosch Motronic M1.0


M5/M635CSI
E28/E24
S38/B35 (260hp kat)
87-88
0 261 200 079
Bosch Motronic M1.0 Motorsport


M5/M635CSI
E28/E24
M88 (286hp)
84-87
0 261 200 055
Bosch Motronic M1.0 Motorsport


633csi
E24
M30/B32
84
0 261 200 008
Bosch Motronic M1.0 Basic


635csi
E24
M30/B34
85-87
0 261 200 059
Bosch Motronic M1.0 Adaptive


635csi
E24
M30/B35
86-88
0 261 200 150
Bosch Motronic M1.1


733i
E23
M30/B32
84
0 261 200 008
Bosch Motronic M1.0 Basic


735i
E23
M30/B35
09/80-09/82
0 261 200 001
Bosch Motronic M1.0 Basic 


735i
E23
M30/B34 (218hp)
84-87
0 261 200 011
Bosch Motronic M1.0 Adaptive


735i
E23
M30/B34
84-87
0 261 200 059
Bosch Motronic M1.0 Adaptive


745i
E23
M102/B34 (252hp)
83--86>
0 261 200 013
Bosch Motronic M1.0

I was able to find a 35 pin connector and received it in the mail today. Here are a few (sorry for the poor quality) pictures of the connectors I received and the test fit into my 35 pin engine harness. One shows the connector next to my 35 pin 073 ECU.

















As mentioned above, on top of this adapter, I am considering sourcing components to create a TPS to vTPS adapter. This would be a similar male to female adapter that could plug into the factory engine harness wiring for the TPS and would allow you to run the e36 vTPS without having to rewire anything. All you would need is the variable TPS from a later BMW.


I could do a similar adapter that would plug in to the factory AFM connector and could be wired to a GM open element IAT sensor. The benefit to all three of these adapters is that they would make everything reversible and you could install a 55 pin ECU, or 55 pin Megasquirt and if you decided you wanted to sell the car without it, or return the vehicle to stock for one reason or another, you could return it back to the factory electronics very easily.


With that said, I would like to gauge interest in this adapter circuit. Who would be interested in one, and if we have enough interest and this first prototype works as expected, maybe we can start a list for a preorder.

[Hit Man X]

I am. Easy for us 745 guys.

[02rollin]

Great, I will keep you updated. The first 55 pin female adapter I received has the wrong housing and will not fit with the 55 pin ecus due to the plastic housing. I could maybe shave it down but I found what I believe is the correct part number which should have the plastic 'receiver hook' which should secure the ecu in place. I will need a confirmed pinout to be able to ensure the adapter is correct. I know there was the m102 and the m106 and want to make sure there is no difference in those wiring pinouts. Do you happen to have these Hit Man?

Here is the first quote I received for the female connector terminals (I could use a couple hundred but not 12000!)... needless to say I believe I found another vendor with a couple in stock and more on order at a reasonable price that I have ordered. Once I have the pinout confirmed with either the e28 or e23, I can test both as my brother has an m106 e23 and my other brother has an e24 and possibly e28 that I can test the adapter on. I also picked up a DIYPnp unit which will allow me to test with.

[Hit Man X]

Oh there is a vast difference in wiring pinouts between both versions of the M102 and the M106. What are you looking for specifically? I have 05/83 to end of production schematics for the M106s scanned and first Gen Ljet to 09/81.

What I am wanting is a 55 pin male to plug into a 55 pin DIY PNP box without looking like a hackjob. I can deal with attaching what needs to go where on my end as I need to tap specific signals only so I can retain my EH transmission. I hope that makes any sense. Hell, I could pay you if you want to make the attachment points. LJ and I have become lazy in our MS conversion keeping the EH trans. Pretty we have it sorted, just limited time.

[02rollin]

Oh there is a vast difference in wiring pinouts between both versions of the M102 and the M106. What are you looking for specifically? I have 05/83 to end of production schematics for the M106s scanned and first Gen Ljet to 09/81.

What I am wanting is a 55 pin male to plug into a 55 pin DIY PNP box without looking like a hackjob. I can deal with attaching what needs to go where on my end as I need to tap specific signals only so I can retain my EH transmission. I hope that makes any sense. Hell, I could pay you if you want to make the attachment points. LJ and I have become lazy in our MS conversion keeping the EH trans. Pretty we have it sorted, just limited time.

Is the M102 only L-jet? Obviously this would be for the motronic engines (M106 only maybe?). I am looking for the pinouts for the 35 pin ecu. I know on the M1.0 e30 there is a separate connector for the tach signal so I assume I would need a separate wire coming off the adapter of that to make it work. Here is what I found for wiring pinouts, does this match what you have? Also it looks like I may need a shielded wire for the CPS. The wiring shouldn't get interference if it is shielded from the sensor to the glovebox, but I may need to experiment with the wiring on the adapter.

http://www.745i.avulan.eu/More/motronic_inter.htm

No:1 * BMW Drawing no: 931 * Motronic 0261 200 013 *
Pin no:	Interconnection numbers	Connected to:
1.1	29, 30, 4.3, 20.4	Ignition Coil -, Connector A, Diagnostics socket
1.2	20b.4	Throttle Switch "952"
1.3	2.13	Knock Sensor Box, Pin no: 13
1.4	35, 22.1, 15.1, 2.17, 38.7, 20.1	Starter relay, Cold start switch, Cold start injector, Knock sensor box, Dashboard connector, Diagnostics Socket
1.5	-	Ground, shielded ground for crankshaft position indicator
1.6	18.4	Airflow Meter "953", ground
1.7	18.2	Airflow Meter "953" , output voltage to A/D Converter
1.8	7.2	RPM Sensor "928"
1.9	18.3	Airflow Meter "953"
1.10	NC	No Connection
1.11	4.1	Connector "A" to Dashboard Computer
1.12	NC	No Connection
1.13	23.1	Engine Temp. Sensor "959"
1.14	16.1, 24.1, 25.1	Injectors 1, 2 and 3 "955"
1.15	12.1, 13.1, 14.1	Injectors 4, 5 and 6 "955"
1.16	39	Battery -
1.17	39	Battery -
1.18	5.3	Relay 2 "966"
1.19	-	Ground
1.20	37.3	Relay 1 "965"
1.21	2.24	Knock Sensor Box, Pin no: 24
1.22	18.1	Airflow Meter / Air Temp. Sensor "953"
1.23	7.3	RPM Sensor, shielded ground "928"
1.24	2.16	Knock Sensor Box, Pin no: 16
1.25	8.1	Crankshaft Position Indicator "929"
1.26	8.2	Crankshaft Position Indicator "929"
1.27	7.1	RPM Sensor "928"
1.28	NC	No Connection
1.29	NC	No Connection
1.30	6.2	Air Pressure Potentiometer "986"
1.31	NC	No Connection
1.32	NC	No Connection
1.33	NC	No Connection
1.34	NC	No Connection
1.35	3.4, 2.25, 5.4	Connector "B", Knock Sensor Box, Relay 2

You will need to help me with the transmission connections. I also don't see any pins for the ICV, what sends the signal to that? It is the knock box? The e30 has those on pins 33 and 34.

Also I believe you are looking for a 55 pin female... the diy pnp unit is a 55 pin male unit, here is a picture of the unit I picked up for reference.

[Hit Man X]

Yes, M102 is an Ljet car. There is a three pin connector on the Motronic 745. Black wire (coil), green wire (I forget), white wire (fuel econ gauge), the best I recall. No ICV on these, just a lame ass slide valve.

Whoops, yes I guess I would need a female 55 pin.

To retain the EH you have to piggyback the -013 Motronic box and retain the knock module, tricking them into thinking they are still running fueling and timing. So, best to my knowledge I will have to steal some pins off of the -013 engine side plug to run to the 55 pin socket and plug the OE Motronic plug back into the -013 box to keep it happy. Now, for guys with five speed swaps or non EH transmissions, this is not needed. Probably would just be easier for them to install a -059 harness and use your adapter.

[02rollin]

Yes, M102 is an Ljet car. There is a three pin connector on the Motronic 745. Black wire (coil), green wire (I forget), white wire (fuel econ gauge), the best I recall. No ICV on these, just a lame ass slide valve.

Whoops, yes I guess I would need a female 55 pin.

To retain the EH you have to piggyback the -013 Motronic box and retain the knock module, tricking them into thinking they are still running fueling and timing. So, best to my knowledge I will have to steal some pins off of the -013 engine side plug to run to the 55 pin socket and plug the OE Motronic plug back into the -013 box to keep it happy. Now, for guys with five speed swaps or non EH transmissions, this is not needed. Probably would just be easier for them to install a -059 harness and use your adapter.

That tach connector is the same as the e30. Is the slide valve a diaphragm with a metal tip that cracks the throttle open? My iX has that but when I bought it, it also had an ICV. I am not sure if the ICV was stock though.

I don't know enough about that transmission to know what you are talking about. It that the sport auto trans where you can select the gear? Will need some ideas if you want this to work by tapping the 'adapter' line to also signal the ecu...



But, Great news. The connectors and pins pins came today so I was able to test fit the components together. The 55 female connector fits properly in the ecu housing and it comes with the locking metal bracket to secure it to the ECU. The female terminal pins seem to fit and slide properly over the male pins of the ECU. They appear to fit but i didn't click a pin into place because I am not sure I could remove it. The next step would be to verify the wiring pinouts and double check whether I need shielded cable for components such as the CPS. I will probably wire this first one up for the 55 pin DIY PNP unit and not the db37 connector.

Anyway, here are some photos of how it is coming together! Note the metal bracket that slides into the housing and the plastic 'hook' on the opposite side that secures it to the ecu very solid.











And here is a quick preview of how it should go together. I don't have heat shirnk for the wires yet and probably won't on this prototype model. I may order some 3 pin connectors to assemble a TPS to vTPS adapter too.

[offroadkarter]

Converting the stock 35 pin plug to 55 to run megasquirt? I'm very interested. I'll be keeping an eye on this thread.

[02rollin]

Time for a weekly update. The first step to making the 35 pin adapter work is ensuring you've got a variable Throttle Position Sensor (from an e36) so the MS unit can interpret the signal vs the original switch style sensor that comes with the cars of the era. I found the bosch 3-wire connector that plugs into the wiring harness and thought i had ordered all necessary parts to make my first TPS to vTPS. When they arrived, it turns out i had 2 female adapters instead of one male and one female. I got the wire seals, terminals, and even found the rubber boot to cover the wires. Unfortunately, after some research and contact with the manufacturer, the male version is not available due to some contract with the manufacturer. There is a drawing from the manufacturer for reference only so you can manufacture your own male connector. :shock:





Here are the 2 connectors I received, probably going to go with the longer run due to pricing differences.





I was able to sleauth my way into a 3 prong male connector and ordered some of those to make sure I have the right male connector to finish the adapter. Here is an example of how it will look. I am working on putting together a TPS to vTPS adapter kit that would include the wiring adapter, the vTPS sensor, and a bracket to mount the vTPS to the m20/m30 throttle body. I anticipate that kit to be ~$100 shipped, or half of that if you sourced your own vTPS.


Here are a couple pictures of half of the TPS adapter harness... waiting on the male connector at the moment. The rubber dust cover costs almost $3 per unit and each adapter would have 2, so I may try heat shrink to keep costs down. The rubber wire seals should keep dust and debris out of the connector so I don't think the rubber cover is absolutely necessary. Any thoughts or preferences?


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[Hit Man X]

Motronic 745i already comes with the three wire TPS due to the EH transmission (and the idle switch just like all the early cars), same as E24/8 cars. B35 EH cars, at least E32/4 I have seen, use that six wire TPS as it integrates both separate items into one unit. One of the guys here tried swapping it on his 745i and it did not work correctly. Something about not being able to set the idle switch to close and keep the TPS voltage in spec I believe.

Dust boot is better, I would gladly pay the extra cash. Looks more professional and durable. Same reason my Tial conversion wastegates are ceramic coated on the factory base and the OE guide is honed.

[02rollin]

Motronic 745i already comes with the three wire TPS due to the EH transmission (and the idle switch just like all the early cars), same as E24/8 cars. B35 EH cars, at least E32/4 I have seen, use that six wire TPS as it integrates both separate items into one unit. One of the guys here tried swapping it on his 745i and it did not work correctly. Something about not being able to set the idle switch to close and keep the TPS voltage in spec I believe.

Dust boot is better, I would gladly pay the extra cash. Looks more professional and durable. Same reason my Tial conversion wastegates are ceramic coated on the factory base and the OE guide is honed.

Good to know, thanks for the feedback on the dust boots. Yes, almost all of the e23/28/30s of the era run the 3 wire TPS (with the exception of the m42 powered e30s running a later motronic with 88 pin ecu)), however it is the 'switched' style with 3 settings (on, off and WOT signal). I have heard of the later automatic switch with 6 pins as an alternative. The original TPS is #13631273265 and supposedly appears on both auto and manual e30,e23,e24, and e28s. The m30b35 auto 6 pin TPS is part number 13631708605 and costs atleast $200 new. A junkyard unit probably would work if you could find one, but it doesn't look like the connector will plug and play, you will have to do some work to get it to hook up to the 3 wire bosch connector.

[02rollin]

I build my first prototype tps adapter and it worked. Here area couple of pictures. I didn't use heat shrink or the rubber dust boots on this one in case I had a problem. Here are a few pictures as well as once I installed it on my car and tested it. Note I am using a homemade adapter bracket not the one that will come in this kit.




















I did a datalog, but ignore the AFR readings as i am running the engine on basically stock Motronic 1.3 with a narrowband oxygen sensor.

[Cannabis9478]

Hi there,

Just wondering is the adaptor loom available for purchase? Or if possible you could let me know a source for the 35 pin male plug?

Cheers

Mike