14 replies to this topic

[Mrio]

Hello Everyone,

 

I have a manual 1994 SPI without immobilizer, but after 2-3 months of fault finding, the car would still not start, The 3 pins diagnostic plug, isn't much help either.

 

So i decided to rebuild the ECU with Arduino (?) and have a better diagnostic output (probably to an attached screen).

 

I have looked up much information as I can. But still struggling wich board to use. Arduino (which one)? Or Raspberry Pi Or Beagleboard OR  ...

 

Has anyone done this before?

Does anyone have the EEPROM code or how the ECU really works, like what are the mappings, etc?

[Mrio]

Allright!

 

I have ordered an Arduino Uno with displays and accessoires and am starting to write the codes. I will keep you guys updated if something comes up.

[FlyingScot]

Would it not be easier to plug your car into a diagnostic set up rather than try to replace the ECU.....

FS

[greenwheels]

Would it not be easier to plug your car into a diagnostic set up rather than try to replace the ECU.....

FS

Some of us just like the challenge

[FlyingScot]

Aye good luck, you obviously know more about MEMS than I do

FS

[Mrio]

Aye good luck, you obviously know more about MEMS than I do

FS

Nope. I have no idea how it works. But I can not afford to pay £300 for a diagnostic tool or a megasquirt system.

Today I have received my £8 serial to usb. Tomorrow i will connect this to the 3-wire diagnostic cable and see if I can find anything through the laptop.

The arduino board will arrive friday. So until then, its either finding information how the ecu work on the injection or removing the EEPROM and reverse engineer it.

The goal is to diy megasquirt for less than £40.

[Alex_B]

Wow, good luck! what knowledge of coding do you have? I am assuming a fair amount as that is a mammoth task! What type of ecu system are you going to replicate? 

[Mrio]

Thanks. I'll be programming it in C. It's alot of work, but i'll start off first by checking the crank sensor and sending a burst of fuel every 10ms.

[xrocketengineer]

This seems interesting. You are going to need a separate MAP sensor since the SPI one is built in on the ECU. Unless you can use a MAF that in the long run might make things easier when creating the fuelling map.

More power to you (and the car)!

[Mrio]

Hey xrocketengineer, thats a good tip! Thanks

 

I've finished programming the fuel injection stuff and the engine is running (really rough). I've already de-solder the MAP sensor and now am figuring out how this thing works and how much fuel to send.

I've found out that sending fuel is not based on the crank sensor (that was only for letting the ECU know when to inject fuel?).

[xrocketengineer]

My general understanding of how a generic fuel injection works is very limited. But this my interpretation: the MEMS system is of the earlier type of electronic fuel injection with no MAF (mass air flow) sensor. Instead it uses a cheaper MAP (manifold absolute pressure) sensor. Therefore, since the ECU knows the volume of air flowing based on the displacement of the engine and RPM. The MAP sensor provides the manifold pressure and the air temperature from the AIT (air intake temperature) sensor. From these two the ECU can guesstimate the air density. With the density and the volume it then calculates an approximated a mass flow rate. Then using the CTS (coolant temperature sensor) the mixture is finally fine tuned based on richer if the engine is cold and leaner if warm. And finally the O2 (lambda) sensor determines if the mixture is stoichiometric (around 14 to 1 air/fuel ratio by mass) since that is what the catalytic converter requires in order to operate properly.

[dbcool20]

xrocketengineer don't forget the TPS or Throttle position sensor in all that. 

Mrio if you are interested in the Rover MEMS system and how it works here is a usefull pdf link: http://www.renegadem...y/RoverMEMS.pdf

[Elliskwleisk]

 

Aye good luck, you obviously know more about MEMS than I do

FS

Nope. I have no idea how it works. But I can not afford to pay £300 for a diagnostic tool or a megasquirt system.

Today I have received my £8 serial to usb. Tomorrow i will connect this to the 3-wire diagnostic cable and see if I can find anything through the laptop.

The arduino board will arrive friday. So until then, its either finding information how the ecu work on the injection or removing the EEPROM and reverse engineer it.

The goal is to diy megasquirt for less than £40.

 

 

You can get small basic diagnostic tools's for around £25.   We have one at work just because it was on sale and cheap but it's strange and surprising how our more expensive systems some times can't read or delete codes and this little box thing can. 

[greenwheels]

 

 

Aye good luck, you obviously know more about MEMS than I do

FS

Nope. I have no idea how it works. But I can not afford to pay £300 for a diagnostic tool or a megasquirt system.

Today I have received my £8 serial to usb. Tomorrow i will connect this to the 3-wire diagnostic cable and see if I can find anything through the laptop.

The arduino board will arrive friday. So until then, its either finding information how the ecu work on the injection or removing the EEPROM and reverse engineer it.

The goal is to diy megasquirt for less than £40.

 

 

You can get small basic diagnostic tools's for around £25.   We have one at work just because it was on sale and cheap but it's strange and surprising how our more expensive systems some times can't read or delete codes and this little box thing can. 

 

Do you have a link to where yo can get one?

[Elliskwleisk]

 

 

 

Aye good luck, you obviously know more about MEMS than I do

FS

Nope. I have no idea how it works. But I can not afford to pay £300 for a diagnostic tool or a megasquirt system.

Today I have received my £8 serial to usb. Tomorrow i will connect this to the 3-wire diagnostic cable and see if I can find anything through the laptop.

The arduino board will arrive friday. So until then, its either finding information how the ecu work on the injection or removing the EEPROM and reverse engineer it.

The goal is to diy megasquirt for less than £40.

 

 

You can get small basic diagnostic tools's for around £25.   We have one at work just because it was on sale and cheap but it's strange and surprising how our more expensive systems some times can't read or delete codes and this little box thing can. 

 

Do you have a link to where yo can get one?

 

 

We have a small one like this. It's not exactly the same as this but it is the same make. I cannot guarantee that this would work because I have never owned a Mini with a diagnostic plug. However, the basic ones, like this, usually just tell you the code (If it can communicate with the vehicle), which you then just look up on google. 

 

http://www.ebay.co.u...=item43bcd2c064

 

Edit: Looks like I've spoken again without knowing what I am on about  I have just done a small amount of research and learned that the SPI had a 3 pin connector and the MPI had a 16 pin connector. Both of which apparently, are not OBD reader compliant. So that link above is no use! I will look in to this and see If I can find something which will actually help.

Edited by Elliskwleisk, 10 July 2014 - 08:33 PM.