M73 Automatic transmission

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JRockland
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M73 Automatic transmission

Post by JRockland »

Im working on a M73 E38 supercharged VIP setup (bagger, limo style driving) and I will be keeping it automatic 100%.

RusEfi seem like a good option for ECU, now I know automatic transmission isnt supported yet..
How can I help, how can we make it happen ?
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AndreyB
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Re: M73 Automatic transmission

Post by AndreyB »

first thing first www.patreon.com/rusefi is one place to help

next please start a separate thread about your vehicle, with more specific details like does stuff currently crank idle run drive.

lastly please spell out your skillset - can you wench? solder? code? do you have an oscolloscope? do you have a multimeter?

do you have time, money or skills pretty much :)
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JRockland
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Re: M73 Automatic transmission

Post by JRockland »

Skillset are mechanic, solder/wiring custom harness, Pcb design/production.
Basic skills in coding (more toward electromechanical).

**I'm French, sorry for my spelling.

Ill get the Ecm open later this week and see if it would be easier for me to make a new one as I can control robotic much easier then trying to understand programmers work. Could be programmed from throttle condition vs rpm.

As for a project page it will depend as if we can make it happen or not, as it is not optional for my built. (I have shoulder issues and can't drive stick shift anymore ... )
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AndreyB
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Re: M73 Automatic transmission

Post by AndreyB »

what is the state of the vehicle? vehicle thread possible with images?

starts? runs? drives?

https://github.com/rusefi/rusefi/wiki/BMW-e38-750#tcu shows five pressure control actuators, this transmission is less trivial than it could have been :(
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JRockland
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Re: M73 Automatic transmission

Post by JRockland »

Engine/tranny is out and cleaned, I think Ill start by mounting the tranny on a bench and connecting it to an electric motor (I have couple of high torque motors around the shot).
From there I can look at options:
Sending code to the tcm from a pi (hard)
Manually trigering the selenoid and learn how it work. Much easier.

There is a pcs tcm2800 module available who is compatible but it would cost about 1k usd with the harnest.. expensive.

Ill start a build page.
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AndreyB
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Re: M73 Automatic transmission

Post by AndreyB »

Please order https://openlightlabs.com/collections/frontpage/products/canable-0-4

While canable is on the way please get engine and transmission to start and run on OEM electronics. You would probably need fuel and coolant and a lot of wires, it might be easiest to assemble everything inside the vehicle not on a bench?
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JRockland
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Re: M73 Automatic transmission

Post by JRockland »

Not a problem, really nice for a can reader.
It is easier to mount it on a bench so when it work I can built a proper harness and make them available ?

Oil/prestone/gas isnt a problem. Security system will be as I will have to get the modules out of the cars.. finding a way to bypass would make it much easier.

I will also need the engine out so I can build the supercharger adaptor plate and mount it.
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AndreyB
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Re: M73 Automatic transmission

Post by AndreyB »

for electronics work please have things in tge car. there is no bypassing and removing whole harness with security modules and gauge cluster does not seem effective.

please get car to run in original complete form
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Simon@FutureProof
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Re: M73 Automatic transmission

Post by Simon@FutureProof »

100% agree, it would be easier to dangle the motor back into the bay to get it fired up, we have seen these units be rather touchy about the connections to some of the modules.

You would likely do more damage getting everything out to run on the bench than it is worth.

Regarding the install of a rusEFI, I personally think it is easier to do all the loom layout with the engine in the car, lift the loom off and tidy up things and fit plugs etc before refitting it to the car.
With the engine out of the car it's tough to get all the lengths right and avoid bad wire runs.

Good news is most 90s onward BMW looms are already pretty good to use for RE with just the main ECU plugs chopped off and new plugs crimped on.
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JRockland
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Re: M73 Automatic transmission

Post by JRockland »

Ill try to find someone with a running 750il.
The body is leaving for the body shop and I have to rebuilt the tranny and exhaust lines before anything goes back in the car. And fit the supercharger.

If it is too complicated Ill leave the old ecu's partially connected where they receive info from the motors but dont control it, so they communicate with the tranny as normal.
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Re: M73 Automatic transmission

Post by Simon@FutureProof »

I think you might get away with taking the CAN messages and transmission info from a 750, 740 or 840. I believe they are very similar and would be surprised to learn of any significant differences in the comms or body modules.

Certainly the ready programmed transmission unit is the same part number on the 750 and 850.

840 and 850 body module is also the same part number.

EML and DME are shared between the 850 and 750 too.
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JRockland
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Re: M73 Automatic transmission

Post by JRockland »

Looking at the harness the easiest way would be to keep the original ECU's, cut off all their output to the motors and give them enough input to make them believe they are in control. This way they still control the TCM.

I had been looking for people around with a similar series car but no luck.

***Actually once that works I can scan the DBUS while driving and record everything.
Last edited by Simon@FutureProof on Fri Mar 26, 2021 10:18 am, edited 1 time in total.
Reason: Merged posts
Simon@FutureProof
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Re: M73 Automatic transmission

Post by Simon@FutureProof »

It is actually easier to spoof the inputs to that generation ECU than it would seem, I have done it on the M3.3 which is the generation before your ECUs.
Can you grab the BMW part number from the 2 ECUs you have to confirm what generation they are and I will try to get some details up of how I have spoofed the inputs in the past. No guarantee that it will work out for you though.
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JRockland
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Joined: Sat Mar 06, 2021 4:20 pm
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Re: M73 Automatic transmission

Post by JRockland »

Will do tomorrow, a company is picking up the engine to built a custom frame so I can run and dyno it in my garage.

While getting it ready I realized 3 of my 4 knock sensors where busted, I guess bosh plastics isn't good for 25 years XD
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