E30 ECU reverse engineering project

[deedub 115]

Just came across an interesting E30 ECU reverse engieneering project on reddit. Sounds like they will open source it at some point.

https://www.reddit.com/r/E30/comments/1jp7sgs/stock_ecu_tuning/

Edited May 29 by deedub

[deedub 115]

DM'd this dude about the setup and got blanked. Think they were just showing off with how smart they are rather than intending to share knowledge about the setup and what they did.

If I get around to having a crack at this I'll post on this thread. Need to learn a bit more first to make sure I don't brick things in the process.

[Driftit 2196]

It looks like simple pulse counting of a hall effect sensor monitoring RPM.
More likely he is simply intercepting some of the sensor inputs.
Was quite common with old piggy back ECU's.

[deedub 115]

2 hours ago, Driftit said:

It looks like simple pulse counting of a hall effect sensor monitoring RPM.
More likely he is simply intercepting some of the sensor inputs.
Was quite common with old piggy back ECU's.

If you have any resources handy around this stuff I's be keen to see it.

This is just a nerd project for me I thought of doing after seeing what that reddit OP did. Wanted to know what that python code behind the terminal is. It's a test file but it probably means he is using python to work with the data.

That's probably the most interesting part to me. What is he doing with the output. How is he working with those streams and what has he learned about it. Probably pointless exercise. But interesting.

[Driftit 2196]

I honestly don't think he would be manipulating any of the data. He seems to be just using the script to visualize and scale the pulse count. You could use this to make a display/gauge.

@hybridan old Bimmersport member on here was building a nice display system for his E30. Have a did back to see if you can find the posts. 

If you wanted to cheat without having to write any code you could pick up an old mapecu2 which is a piggy back and use their UI to monitor anything required for tuning or switch/trigger states. 

 

[deedub 115]

2 hours ago, Driftit said:

He seems to be just using the script to visualize and scale the pulse count.

That makes sense.

The part where OP says "lie to the ECU" though seems to suggest some kind of manipulation of input to the ECU. But there's a high chance I'm just misunderstanding the claim in the context of ECUs and how they work.

And the OP claim about being "close to fully reverse engineering the data stream from the ecu" is the other part that is confusing me a bit as well.

Lying to the ECU and reverse engineering the ECU data stream suggests to me more is being done here than intercepting sensor data? 

I have a mental model built up in my head around how these parts are connecting up and I'm probably way off. I'm probably making assumptions that don't apply in the ECU realm.

I'll look up Hybrid's work. I'm sure I'll learn a bunch from those posts. I need to also familiarise myself with other fundamental things like CAN bus etc. It's all new to me and I could be tripping up over terminology as well.

Thanks for the info around piggybacks. I'll look into those.

 

[deedub 115]

On 6/14/2025 at 11:31 AM, deedub said:

Think they were just showing off with how smart they are

This comment at the end of OP post:

"PSA: don't try this if your an idiot"

Whatever genius.

No one is just gonna stumble into wiring up a raspberry pi into a car from the 80's. Plus he didn't share any actual useful info. 

Edited 18 hours ago by deedub

[Driftit 2196]

2 hours ago, deedub said:

This comment at the end of OP post:

"PSA: don't try this if your an idiot"

Whatever genius.

No one is just gonna stumble into wiring up a raspberry pi into a car from the 80's. Plus he didn't share any actual useful info. 

Yeah this is what makes me suspicious of his claims.
Nothing he is doing there is any form of manipulation.

Jaycar use to do a kit that you could build that allowed you to intercept the A/F input and output whatever you like (lying to the ECU).
I had one of these kits back in the early 2000's.  Without a wide band A/F sensor you are risking your motor.  I found out the hard way.  The unit failed and ran my motor lean while at the track.  Piston melted.

I have a piggy back MAP ECU2 in my E34.
It is probably going to be replaced as I develop the car.  But it has been good for what I am doing.
https://map-ecu.com/

[deedub 115]

Lots of good info. That sounds like I should actually get a cheap ECU and use that directly. Definitely don't want to mess with the motor for an experiment.

Guessing there are ECU simulators as sell (that map-ecu project looks interesting).