DME - converting to 1989 8K chip

[scarceller]

I have converted a 1986 DME to use the 1989 8K EPROM chip, so I decided to write this up.

DMEs from 1986-1988 use a 27c32 UV-EPROM this is a 4K (4096 bytes) with 24pins UV Erasable Read Only Memory chip.
The early 84-85 DMEs used a 27c16 2K chip, also 24pins.

Then later in 1989 they used a 27c64 UV-EPROM this is an 8K (8192 bytes) with 28pins. You can also use a 28c64b EEPROM which is electrically erasable and very nice if you need to quickly reprogram these.

The 84-88 DMEs all had the main program code burned into the 8051 Processors internal 4K memory while having all the maps and some code in the external EPROM but in 1989 the factory moved to no longer use the Processor’s internal Memory and all the code and maps where burned into the 8K chip for the 1989 model cars. The 1989 main code had several improvements as well as better ignition maps that resulted in more power for the 89 cars. The 1989 factory chip was more aggressive than any of the 84-88 chips. For this reason you may want to simply plug a 1989 factory chip into the older 84-88 DMEs.

To upgrade a DME to 1989 chip you need to:
1. Unsolder the 24pin EPROM socket and replace it with a 28pin socket.
2. Place a jumper across B700 (see picture)
3. Finally install a 1989 8K chip into the 28pin socket.

Ignore the red/black/yellow wires as this is a kill switch I wired to easily disable my DME.


Once you do this the internal 8051 Processor Code is ignored and is instead read from the lower-half of the 8K chip, the upper-half of the 8K chip contains the maps and some code. Simply, in 1989 they no longer use the 4K ROM within the 8051 Processor.

NOTE: if you have an older 84-85 DME with a 2K chip you need to first upgrade it to a 4K chip. See this link for details on this 911Chips.com - Porsche 964 and 993 Strut Brace (courtesy of Steve Wong) This mod will upgrade the 84-85 2K DME to the 86-88 4K DME after this you can then upgrade further to the 1989 8K setup.

[laundromatt]

Thanks for the writeup. As an '84 owner, this is of some interest to me.

I haven't taken mine apart to look, but... if you take out the existing 24 pin socket, won't you have 24 holes? If so, how do you fit a 28 pin socket into those 24 holes? A picture of the other side of the board would be helpful, if you haven't closed it back up already.

Also, what is the cost of a used 1989 stock chip? Just trying to see if it's that much cheaper than one of the performance chips already out there on the market.

[scarceller]

The boards all have 28 pin holes but most DMEs only have 24 pin sockets installed. When you open the DME you'll see what I mean. The 28 pin area is even marked for the 4K or 8K chip!

But if your DME is a 1984 then it also needs the other mods to bring it from 2K chip to 4K chip first.

You can get a 1989 chip from many places as many folks replace these with aftermarket. Steve Wong may even burn one for you. If you are really stuck I can burn you one for tiny fee.

As for aftermarket chips I'd only get a Steve Wong chip. I have tons of knowledge on these DMEs and burn my own chips all the time. I have seen several aftermarket chips (won't mention names) that are scary in how far they push timing. The only chip I'd conciser is SW!

But replacing a 84 2K chip with the 89 factory chip will really change your ride. Go lookup the HP rating for the 84 and 89 cars, same motors but the 89 cars have more HP - the chip is the only big change I know about. I also know first hand why, the timing in the 89 chip is more aggressive than the earlier chips.

Originally Posted by laundromatt

Thanks for the writeup. As an '84 owner, this is of some interest to me.

I haven't taken mine apart to look, but... if you take out the existing 24 pin socket, won't you have 24 holes? If so, how do you fit a 28 pin socket into those 24 holes? A picture of the other side of the board would be helpful, if you haven't closed it back up already.

Also, what is the cost of a used 1989 stock chip? Just trying to see if it's that much cheaper than one of the performance chips already out there on the market.

[gshiwota]

Thanks for the great write up. I used your write up and upgraded my '86 this weekend to a 28 pin SW chip. I wanted to add one more thing that saved me time on the install.


Instead of removing the 24 pin socket and soldering in a new 28 pin socket, I simply soldered in the additional 4 pins next to my 24 pin socket.

I can't take credit for this idea as I found this info from a guy that upgraded his 944 DME.
86 to 88 Conversion ML3.1

I could not source the individual socket pins so I bought a 8 pin socket and basically cut the plastic so I ended up with two 2-socket connectors (one for each side of the chip). Unfortunately I didn't take pictures of the install however the site link above pretty much is the same thing.

The total install time took 30 minutes and this included removing and reinstalling the DME and starting the car up for the first time. Easy and the best bang-for-the buck upgrade I have done to my car.

[John Galt]

Originally Posted by scarceller

You can get a 1989 chip from many places as many folks replace these with aftermarket. Steve Wong may even burn one for you. If you are really stuck I can burn you one for tiny fee.

What is the part number for the 89 chip? Could you burn one?

[GH85Carrera]

I just seems funny, the big upgrade is from 4 Kilobytes to 8 Kilobytes. Now days a simgle photo from a cell phone is thousands of times more data.

[nospiners]

i wonder what the drivability improvement is ?? is it really worth it if you have a good running vehicle ??

[GH85Carrera]

Originally Posted by nospiners

i wonder what the drivability improvement is ?? is it really worth it if you have a good running vehicle ??

My understanding is the increased HP of the later cars is from the new fuel map. I have a Steve Wong chip and he or the other programmers can tell you the precise difference in power or driveability. My 85 starts, idles and runs great in all conditions, from well below freezing to 110 degrees.

[mysocal911]

Originally Posted by GH85Carrera

My understanding is the increased HP of the later cars is from the new fuel map. I have a Steve Wong chip and he or the other programmers can tell you the precise difference in power or driveability. My 85 starts, idles and runs great in all conditions, from well below freezing to 110 degrees.

Not really! Here're data to prove it:





It's all about increasing the ignition timing and NOT tweaking fuel maps!

[2.7RS]

Good for the street and red light racers.

You think Porsche Ing just left some ponnies on the table just because

It will detonate and cook your heads and pistons.

Don't track it.

[mysocal911]

Originally Posted by 2.7RS

Good for the street and red light racers.

You think Porsche Ing just left some ponnies on the table just because

It will detonate and cook your heads and pistons.

Don't track it.

But then you have non-track issues to contend with;

1. a very hot day
2. no high octane (only regular) while traveling
3. a long high grade mountain climb

That's why all new vehicles have knock control, just like the 964s/993s of the '90s.
Those engines have ignition timings in the low 40 degree advance areas.

[917_Langheck]

Originally Posted by 2.7RS

You think Porsche Ing just left some ponnies on the table just because

Yes, yes they did, just because. The because was Federal, and particularly California, smog rules. Every manufacturer selling cars in the US has had to leave power on the table due to changes in smog, and later CAFE, rules since the late 1960s.

[2.7RS]

Gentlemen don't get off track.

We are talking about 1983-1989 Carrera with Bosch Motronic. Nothing else

[mysocal911]

Originally Posted by 2.7RS

Gentlemen don't get off track.

We are talking about 1983-1989 Carrera with Bosch Motronic. Nothing else

Right! And it's all about changing the ignition timing maps and NOT the fuel maps for the gains. It's that simple based on the data!

[darrin]

2.7RS and Dave -- My read of the original post on this thread is that didn't really address aftermarket/tuner chips. Instead, it discussed the advantages that could be realized by modifying/"upgrading" a older Carrera DME so that it could accept the chip Porsche included with 1989 carreras. "The 1989 main code had several improvements as well as better ignition maps that resulted in more power for the 89 cars. The 1989 factory chip was more aggressive than any of the 84-88 chips. For this reason you may want to simply plug a 1989 factory chip into the older 84-88 DMEs."

Looking at stats on the web, it looks like, even though compression and displacement remained unchanged, 87-87 US spec carreras are rated 10 bhp and 3 lb ft higher than the 84-86 carreras (See, e.g. https://www.stuttcars.com/porsche-911carrera-3-2-1984-1989-specifications-performance/), which appears to lend some credence to the OP's comments/statements and similarly suggests that if the balance of the 3.2 Carrera engines were unchanged between the 84-86 and 87-89 3.2 engines, Porsche DID, in fact "leave some ponies on the table, just because."

I recognize the issues you've identified regarding aftermarket chips that push the limits too far, but would be interested in any further clarification you may be able to provide regarding the apparent chip "tweaking" porsche itself performed with the 3.2 and/or whether the rated hp/torque increases for 87-89 carreras can be attributed to something else.

[mysocal911]

Originally Posted by darrin

2.7RS and Dave -- My read of the original post on this thread is that didn't really address aftermarket/tuner chips. Instead, it discussed the advantages that could be realized by modifying/"upgrading" a older Carrera DME so that it could accept the chip Porsche included with 1989 carreras. "The 1989 main code had several improvements as well as better ignition maps that resulted in more power for the 89 cars. The 1989 factory chip was more aggressive than any of the 84-88 chips. For this reason you may want to simply plug a 1989 factory chip into the older 84-88 DMEs."

Looking at stats on the web, it looks like, even though compression and displacement remained unchanged, 87-87 US spec carreras are rated 10 bhp and 3 lb ft higher than the 84-86 carreras (See, e.g. https://www.stuttcars.com/porsche-911carrera-3-2-1984-1989-specifications-performance/), which appears to lend some credence to the OP's comments/statements and similarly suggests that if the balance of the 3.2 Carrera engines were unchanged between the 84-86 and 87-89 3.2 engines, Porsche DID, in fact "leave some ponies on the table, just because."

I recognize the issues you've identified regarding aftermarket chips that push the limits too far, but would be interested in any further clarification you may be able to provide regarding the apparent chip "tweaking" porsche itself performed with the 3.2 and/or whether the rated hp/torque increases for 87-89 carreras can be attributed to something else.

So Porsche tweaked the ignition maps too, but as not aggressively as the "tuners" did in later years! It's not that complex to understand based on the data.

[wazzz]

I'm a bit puzzled about the 2K, 4K, 8K initial discussion above. It implies that 87 and 88 Carrera both have a 4K, and that only the 89 version was fitted with a 8K.

But it can be seen on the Motronic schematic for the Carrera 1987 that a 2764 (28 pins) is used. That's a 8K.

I am referring to the Bosch schematic that is available as 2 PDF files, one for the analog part, one for the digital part. This is Bosch part # 0 261 200 085, Porsche part # 911.618.111.

Any insight about this?

[mysocal911]

Originally Posted by wazzz

I'm a bit puzzled about the 2K, 4K, 8K initial discussion above. It implies that 87 and 88 Carrera both have a 4K, and that only the 89 version was fitted with a 8K.

But it can be seen on the Motronic schematic for the Carrera 1987 that a 2764 (28 pins) is used. That's a 8K.

I am referring to the Bosch schematic that is available as 2 PDF files, one for the analog part, one for the digital part. This is Bosch part # 0 261 200 085, Porsche part # 911.618.111.

Any insight about this?

You are correct! Here in the U.S., the late '87 and all '88s had the 8K (358).

[3literpwr]

I have 3.4 with a FR wilk chip from ages ago. It's got 20/21 cams and measured at about 10.3:1 with CP wedge pistons. I think I need to pull that map out and go back to stock or get another burned. My car is an '87 with 24 pin chip.

[almostordinary]

Following... I have a hodge podge build.

87 body
88 motor
89 G50.01
24pin 87 DME.