ECU EPROM Chip - What does it do?
 

Hey guys

Been looking into exactly what data is stored on the EPROM chip in the ECU - at the moment I can't find a cohesive report or maybe nobody knows exactly.

The chip I mean is the removable one on a Magnetti Marelli 8P ECU (S1 & S2 Rallye, 1.6 XSi)







Rumours vary wildly from the ECU's idle program, the immobiliser code/bypass or even a map of some description.

Any experience would be appreciated

Mike

now i may be wrong but im gonna kinda answer you with what i know about removable chips etc from a honda ecu.. if that is the chip that is removed and possibly replaced when ur wee french froggy is remapped then i can only assume that it holds a map of some kind, air/fuel, lambda etc etc

Eprom stands for: erasable programmable read only memory

Id guess, this is only a guess that it stores your cars map for your idle control etc, so im tipping when your car is remapped this is the chip that is reprogrammed

For the transponder too your key their is a transponder ring near the ignition somewhere.

Cheers for the input mate :y:

On the upside it seems the EPROM itself is a fairly standard component, can easily google and find the pin breakdowns. It has 15 inputs and 7 outputs, 512Kbit storage capacity. Good to know, lol

If someone with experience in mapping can tell me an engine map needs more than 512Kbit of storage space that's one rumour down already.

When I say transponder I mean the keypad immobiliser. Slip of the tongue (keyboard). Just edited the 1st post

Im not sure about the storage, as 512Kbit may not sound alot, but am guessing when its processing the maps they are very small compared to what processes a computer has to deal with. Infact i could guarantee they are much smaller, not sure of any figures but im sure a quick search online may bring up some info

512Kbit is only 64kb, in real money. The spec for the chip suggests it stores 64,000 8-bit entries.

Considering a map has 3 components - RPM, Load and Fuel

From what I can tell an engine map for this KMS - http://forum.205gtidrivers.com/index...howtopic=67871 would require a 25 x 15 data grid, each containing a 8 bit value (although the ones in this particular example are 3sf decimals, surely this would require 16 bit data else you'd be limited to a maximum value of 25.6?)

Anyway, 25x15 is much less than 64000 (375). Even with 16-bit data that's still only 750b of information, ~10% of the total EPROM storage.

what is it your actually looking to gain from your findings mate? is it the immob your trying to sort? or actually interested in the mapping itself for another chip?

All of the above.

You wanting to put that map/figures on your standard ecu EPROM?

No, just want to know what it does since it's easy to change them between ECUs

I'd guess it wouldn't be hard to interchange them, but for sake of it I would just swap the whole ecu

I'd not try taking a chip from a single plug ecu and put into a 3 plug.... Even if chips were same I could imagine some slight alterations and differences in software or how the chip is run or even the usage of input and output terminals on the board

*sigh* This is why I just asked a question instead of explaining what I was doing, with all due respect I don't need nor want people's opinions on what I'm doing with it.

They ARE easily interchangable, in fact I've already swapped the one from a 1.3 Rallye to a 1.6 Rallye EPROM on the advice on one member, I'm just looking for a second opinion and more details if they are out there.

They're both Mg Marelli 8P ECUs, they're both completely compatible. No mention of 3 plug, VTRs or anything.

its like a flash drive for the ecu basically. Stores whatever data is required for the ecu to work, theres no set format so swapping them around could prove difficult even if they are the same size and part number.

Just like with a flash drive if youve got 4gb you dont need to fill it. You often find whitespace at the end of maps etc.

Okay ryan, so can you clarify that the ECU being locked or unlocked has nothing to do with the chip?

I cant say for sure with the 8p, but i very much doubt it. Its usually in the MCU as they often have a few bytes of memory with them too, they're often locked aswell and you need a code to read/write to them which is a pain in the arse.

Sorry for trying to give some input and help!
I was never saying they were not interchangeable
All i was stating is i do not think it is advisable, and who ever said its fine really shouldn't tell you that. Your decision what you do with it in the end, though a simple thing like a static from you touching a pin etc could kill the eprom. I know this since ive done it myself swapping them over on cnc machines and robots etc

That's great Ry, as I've swapped the EPROM from a locked 8P.16 to a unlocked 8P.40 and was having brown trousers about it.

The engine isn't built yet so naturally I can't test if it's going to lock up or it'll actually fire. It's at least good to know it's not usual for that information to be stored in the chip. If the engine doesn't fire the injectors at least now it seems the ECU is less likely to be the culprit.

I have it on second hand experience (ie dodgy idle/ EPROM switched/ good idle) that the EPROM contains the idle map, hence my motivation for the switch as I'm running 1.3 management on a 1.6, and the conversion has a history of dodgy idles before remap. Does the EPROM containing the idle map sound plausible to you?

And MJ05LLY I didn't mean to come across like that, I'm just looking for a definitive answer. When you've been reading every thread you can find on the RR I guess a bit of grumpy rubs off, sorry.

I was also a little bit insulted you thought I had a VTR. You're still not forgiven for that haha :p

the eeprom contains the entire map, rev limit n all.

If its even slightly different to the original map (not the tables themselves, but size, location and checksums etc) then it probably wont start, this is usually indicated by having all the symptoms of a totally dead ecu. An example of this is the 1ap.81 and 1ap.41 have interchagable eeproms, but the 1ap.10 will not interchange.. even though its the same ecu internally with the exception of a few extra injector drivers for the gti6

If you remove your transponder box before fitting you dont need to worry about trying it with the immo either way.

Bloody excellent.

So 1.3 ECU with 1.6 EPROM on a 1.3 top/1.6 bottom hybrid will happily use all the 1.3 sensors, but then the idle and fuelling is correct for the 1.6 block. That's a bonus - I was only expecting it to fix the idle, not the fuelling as well.

Another member has done it first and has been running the engine for months now, so it all seems to be green lights on whether the hybrid ECU is compatible.

Cheers mate, invaluable :D

it's no problems bud
I was just using a VTR as example wasnt saying you had one

Good luck all the same bud. :y: