Tampa 928s

Mike has loaned me his LH and upon opening it to use my 24 pin chip to test it for him I found it uses a 28 pin chip.
The white tag says: part # 92861812304 965
The Bosch jetronic tag "purple" says 928.618.123.04 part # 0 280 002 503.
So what does he have a 2.3 or 2.2 or a mystery unit .

Fabio421

http://www.mailordercentral.com/928i...618%20123%2004

Tampa 928s

Thats the one but the chip pins are not correct 28 pins vs normal 85-86 24 pin. I wonder if the cover may have been changed? My 85-86 has 24 pins I wonder about the newer 2.3.

PorKen

LH2.2 has a 25 pin external connector. LH2.3 has a 35 pin.

The revision 4 boards have room for a 28 pin chip, but have a 24 installed. Maybe it's a rev. 5 board. Take a pic!

Rev. 3 and 4 boards, click for larger.

Tampa 928s

It looks like the bottom board except the socket is a full 28 pin. The chip is out and the first and last pins are usually B+ and ground respectively. If I insert a 24 pin chip looking at you board in that would mean I would need to place closer to the inside. I don't want to fry a chip due to the voltage being on the wrong pins.

dprantl

I remember John Speake mentioning in another thread that the early '85 LH had 24pin chips, whereas the later ones had 28pin chips. Or maybe I read it in the Sharktuner manual, can't remember which.

Dan
'91 928GT S/C

John Speake

So if you use the chip that's in it already, how does your car run ?

I've not seen a Ver 5 board, but it sounds as though you need a "special" chip made in 27C256 format.

Tampa 928s

As far as I know this Lh has never been tested, Firemed bought it for his flooded 86. He had a chip installed when he purchased it and I noticed the difference in pin outs. I am now using the chip that was in the Lh but never hooked it up. It is possible a chip was just placed in the socket or it actually worked but the placement is important as to not damage the chip.

Tampa 928s

I put the chip in and car runs with it back toward inside of board.
I have a Maf coming with a custom trim pot should arrive tomorrow.

dprantl

I made a trim pot for a MAF on another car a few years back. It was real easy, just find the wire that sends the signal in the harness and splice a pot in there. May not want to do that on a 928 though

'91 928GT S/C

Fabio421

You say it runs. How well does it run? Any change?

Sailmed

Hey Mark,
I could just bring my motor and you can install the SC on it - of course I would need it back once you get it sorted out

Fabio421

Are you sure that the chip that was in this "mystery LH" was a 28 pin chip? Do you still have this chip? The reason I ask is that the 2nd picture above shows a board with 28 pins but only a 24 pin chip installed. Are you sure that yours wasn't this way?

Tampa 928s

This was Mikes board I tried to repair his the swap was a mistake.
I found that the difference between the 24 versus 28 pin is that the 24 pin keeps 8k of code 1/2 in the eprom 1/2 on the controller. The 28 pin keeps all the data on the eprom.