DME Chip Problem
 

A friend of mine has an `85 Euro 3.2 The car ran very strong up to 5600 rpm and then interrupted like a rev limiter was kicking in. He changed the cap, rotor.... and it still ran only up to 5600.

He pulled the DME and tried to check to see if had an aftermarket chip and found a chip that had a small glass window in the center of it with what looked like a tiny silicon circuit chip under the glass (marked NEC and Japan). To make matters more uncertain, the DME had some marker pen writing on the outer case which makes him wonder if it has be swapped out.

When he tried to pry the chip out it busted!:eek: Most of the prongs broke off the chip when it broke and he had to pull the prongs out of the board with a needle nose plier. It appears that he had a chip that was soldered in. He has another stock Motronic chip but it is for a US car. He tried putting it in the board but the prongs of the chip don't go down into the board (more evidence that the old chip was soldered in although we thought they were only soldered up to `84). He tried to put the US chip in to see if it would work but it turns over but doesn't fire and the chip won't stay in place very well. When you hold the board up to the light, some of the holes have light coming through from the solder side and others don't.

His questions: Can he just carefully drill out the holes or solder points on the flip side of the board with a tiny drill bit or does the new chip have to be soldered in as well? Can he use a US chip with a Euro motor? How can he tell what is currently in the car (at least what's left of it)?

Any and all help greatly appreciated but please answer from expertise or experience versus "I think" or "it should"

You need to wick the solder out with an soldering iron and solder wick. If you drill you run the risk of damaging the pc board of the Motronic unit. He must have really pried hard to get the chip to break. The chips are hard to break. Yes it would need to be soldered or a socket soldered in place to put the chip in.

I would contact SteveW at www.911chips.com and have him put in a chip socket and get a performance boost while you are at it. If he damages it any more it will cost way more than sending it in to Steve and getting it done right.:D

I just took the stock chip out of my 1985 today. Under the label, the stock chip (labeled 1267355102) did have the small round window, with the tiny chip under it, just as you describe. It was also labeled NEC Japan, but had no marker pen writing.

I can shoot a photo later if it helps.

And, Steve at 911Chips is a great resorce.

Paul

Those chips aren't supposed to be soldered in except in some 1984s when the factory did that. don't solder the new chip in it should just gently snap into place. A US chip will probably run the car but won't be able to support the freed up exhaust and the higher compression engine and will lose power. Other words, its a waste of time to try it.

I am looking at the stock chip from my 85 carrera and there is no glass window like you guys say. anyway, I afraid he might need a new ecu, again steve at 911chips.com is always a good resource

Jim

The fact that the chip has a window tells you you are dealing with a UV-erasable EPROM. The marking is the manufacturer. It doesn't tell you what was on the chip. Some later pin-compatible PROM's do not have the window and you can not erase them.

It sound like your buddy ripped the chip out of the PCB board rather than out of a socket. This is bad. He most likely did pull some of the through-contacts (for lack of a better word) out as well. These through-contacts connect the coper traces on the top to the ones on the bottom. To fix this properly you need an antistatic de-soldering pump and good soldering skills to remove the remaining solder from the filled holes. I would NOT use solder wick. Next you want to inspect which coper traces and patches have been damaged and repair them. Then solder in a DIP-24 or DIP-28 socket. I would leave this to a professional. Otherwise chances are the DME becomes a paperweight.

Good luck,
Ingo

Why not try to replace it with a used euro DME?
ischmitz is absolutely correct regarding the soldering and traces.
If there are any ESD sensitive components on that board and you go at it with an incorrect type soldering iron, might as well slap some butter on it, cause it'll be toast.

But he didn't replace the ignition cables???

Joe

Some, after reading the posts, would agree that the issue is chip related and not plugs, rotor, cap...Beru or Magnecore wire sets are NOT $20 items.:eek:
I wouldn't have changed them either, based upon what the guy was trying to achieve.

For reference, the following photos are of the stock chip from my 1985, with the label peeled back. The chip number is a stock number, and the DME showed no evidence of being opened before I opened it yesterday.

Paul
http://forums.pelicanparts.com/uploa...1175437627.jpg http://forums.pelicanparts.com/uploa...1175437640.jpg

Paul,

according to the laser marking this is a 2kx8bit EPROM made my NEC in Japan in the 12th week of 1984. This is all you can see. There is no way of telling what is actually written to the chip. You have to read it in an EPROM programmer and look at the code.

BTW, be careful and do not expose the chip to direct sunlight for too long. The quartz window needs to be covered to not erase the chips memory content. Especially as these chips come of age chances are that bits start to "tumble" and exposing the window to sunlight or other UV sources will accelerate this process.

Cheers,
Ingo

Thanks Ingo -- I should have thought of that. The label is back in place, and the chip itself is safely in the nice little plastic case that Steve Wong ships his chip in.

Paul

100% agreed. Send it to Steve Wong.

I'd be doin' plug wires too, BTW.

At this point it's best to convert it to a 28 pin DME ECM which is basically
what a performance chip attempts to do. This also results in an overall better
running engine without the potential problems of a 24 pin performance chip.

Besides major fuel & ignition map changes, the 28 pin DME ECM has changes
to the overall Motronic engine management algorithms. As an example, the
idle system has less of an undershoot on decel and the engine starts better.
These Porsche/Bosch upgrades resulted in the best overall running 3.2 911,
i.e. '88/'89, of all the '84-'89 911 3.2s.

Bottom line: All 3.2 DME ECMs should be converted to a late 28 pin DME ECM
and not waste money with 24 pin performance chips. This is a VERY significant
improvement noticeable from the moment the engine is first started after
the conversion, i.e. the engine will idle smoother and be more responsive
especially when cold.

Also, send the DME ECM to Pelican Parts as they have many suppliers capable of
reliable & quality repairing and/or upgrading the DME ECM.

If he yanked on this board that hard to pry a soldered in DIP IC out, I would suspect now that board may be permanently damaged.

First, are all the board contacts even still present? If so, I would solder in a DIP socket. You can find these off digi-key or mouser or whatever.

The chip is definitely a goner and you will need a new IC.

Even if you replace the IC, there could now be a broken trace or open via somewhere else on the board.

I don't see anything out of the norm with the original chip, it's manufacturer, the fact that it was an UV PROM, or that it was soldered in as the factory sometimes did.

I think you friend may have damaged something that never had anything wrong with it to begin with.

Thanks for all the info.
PSJoyce: Yup, that was the chip before he broke it (but it had a round sticker over the window).
Loren: I see what you are saying about the 24 vs 28 pin chip.

The first thing he'll have to do is see if the board is toast from ripping the old chip out. Can anyone tell me if its possible that he had the factory DME with a soldered chip in an `85 Euro or is that an indication that the unit has been replaced?

Hey Joe,

Besides the incurred chip problem, sounds like your friend is experiencing issues with the speed sensor. After getting the chip/DME problem fixed, I would suggest him to take a look at the gapping between the speed sensor and the fly wheel.

I spent alot of money, headaches, and time chasing the exact problem (replaced DME chip, DME itself, plugs, wires, cht, AFM, most ignition related parts, and even new Speed and Ref sensors). It turned out that my speed sensor was gapped to close to the fly wheel and causing a misfire that acted like a rev limiter at the exact RPM every time (~4800).

If he has no luck finding ROW DME or repairing his, I do have my extra DME if he wants it. I was planning on keeping it, but I guess there really is no need for it anymore as my Rev Limiter problem was the speed sensor gap.

BTW, your friend will be amazed at the difference in HP between RPM's at 5600 vs redline (near).

I bet Steve Wong could repair and make a chip for the Euro 3.2. I just reinstalled my Autothority MAS with Steve's chip for it and it runs very strong!

Good luck,
Darrell

You would have had to read the contents of the IC, but now that the IC is permanently damaged, that is not feasible.

It seems more than possible to me that the factory could have soldered in the original DME in 85.

I would have someone else put a new chip socket in - it sounds like he's not too much of a master with the soldering iron...

-Wayne

Are you sure he was prying on the chip and not the socket that the chip is installed in? Can you post a picture?

Regardless, it sounds like you need a new socket. Send it off to a professional and get it upgraded.

Key EPROM differences of Euro (24) vs USA (24) vs USA (28):

Timing Maps

Idle - Euro(24) & USA(24) are the same, USA(28) a few degrees more advanced
Part Throttle - Euro(24) is a few degrees more advanced than USA(24) with
slight differences with the USA(28)
Full Throttle - USA(28) is a few degrees more advanced than both 24 pins

Fuel Maps

Idle - Euro(24) is slightly more rich than both USA chips
Part Throttle - Both USA chips are slightly richer than the Euro
Full Throttle - Slight differences between all three

There's very little difference between the Euro and USA chips as can
be explained by the higher CR of the Euro engine but then offset by
the higher octane availability, i.e. the ignition timing is basically the
same.

"Can anyone tell me if its possible that he had the factory DME with a soldered chip in an `85 Euro or is that an indication that the unit has been replaced?"

Basically all the early 3.2 DME ECMs had soldered in EPROMs.

"Yup, that was the chip before he broke it (but it had a round sticker over the window)."

Bosch always used a rectangular sticker as posted earlier which indicates
that the EPROM might have been replaced or the sticker was.