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.
Code:
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.
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