Reprogramming computer ECU

This is a discussion on Reprogramming computer ECU within the Networking/Device Communication forums, part of the General Programming Boards category; Hi, I have a 2002 subaru engine and i want to reprogram/tune the engine e.g. flat-foot-shifting, launch-control, rev limit ect. ...

  1. #1
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    Reprogramming computer ECU

    Hi,

    I have a 2002 subaru engine and i want to reprogram/tune the engine e.g. flat-foot-shifting, launch-control, rev limit ect. is it possible to plug my laptop directly into the ecu and tune it? any thoughts would be awesome.

    no negativity, obviously its possible so i don't want to hear about voiding warranties and how hard it'll be or that i can just buy an ecu tuner from a shop. I know.... this is a fun project to see if it can be done.

    thanks

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    Just a wee bit negativity...or really, more being smart-a$$
    Quote Originally Posted by allstar868 View Post
    is it possible to plug my laptop directly into the ecu and tune it?
    Why ask? Apparently you know the answer:
    Quote Originally Posted by allstar868 View Post
    no negativity, obviously its possible
    That being said, there is probably not an "plug in your laptop here" port on the ECU. I doubt anybody is putting USB ports on their ECUs, especially in 2002. There might be a serial port (or header), but even that is unlikely. You will need some sort of hardware to interface between your laptops ports (e.g. USB) and whatever type of port is on your ECU (OBD2?). If you don't buy a device, you must design one yourself. A relatively simple uC with a few extra parts for sorting out the logic levels, etc, could do it. You need to know the interface specs of the ECU to build your device.

    Then comes the part of reverse-engineering/hacking the ECU. You need design documentation from Subaru, or something that tells you what addresses in the ECU are for what set points/limits. Then your software must tell the hardware what values to change, and the hardware must turn that request into the right electrical signals and protocol for updating those values.

    Note, there are a lot (and I mean a lot) of ways to seriously break your car doing this. Everything from not running well, to not running at all to permanent engine and transmission damage, etc. I suggest you get a spare ECU from a junkyard or something. Keep yours in working order, and tinker with the other one.

    Also, I feel obligated to say that, while I am not a lawyer, you probably stand a good chance of doing something illegal here (depending on the degree of your modifications and reverse-engineering). Reverse engineering is often illegal, on the grounds that it is breaking some intellectual property laws. And significant modifications to your car may actually make it illegal to drive on the roads in your state. It could be very, very bad for you legally if something crazy happens while you're driving, and you cause an accident. Not to mention personal and property damage occurring to yourself and others.

    Those last two paragraphs are not "negativity", just honest opinions regarding side-effects of this kind of work.

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    well ive found software and adapters to plug USB to OBD2 like this one pyOBD - Open-source OBD-II diagnostics
    my only problem is that this doesnt say whether or not it can "Tune" the ECU, it looks more like its just a monitor for how the engine is running. Im looking for some way to add parameters like flat-foot-shifting and launch-control like this system: MegaSquirt | Engine Management System | Electronic Fuel Injection - DIYAutoTune.com

    there are already systems out there to do what i want but the cheapest one i could find is like $800 up to $3k or more for a race spec tuner. Its just a project so i dont want to spend that kind of dough on it. if i can do it with just a few cables and alot of programming time then im cool with that haha

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    Most likely you can't. OBD2 is On Board Diagnostics version 2. AFAIK, it's for monitoring only, not changing operational parameters. Of course, my daily driver has OBD2, but I don't mod it. My car that I mod doesn't have an ECU ('68 Firebird, FYI) .

    If you don't want to drop $1-3k for the goods yourself, look for shops around you that will do the tuning for a lower price. I feel like $100-200 might be reasonable for ECU tuning. Ask around on Subaru forums, and check the usual (ebay, craigslist, etc) for used devices. Also, a quick Google search turned up this: Amazon.com: Total OBD & ECU Auto Diagnostics Software (TOAD) + ELM327 USB Cable: Software. Looks cheap, but no guarantees how much it will let you tune.

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