Skwerl

I posted a thread recently about a DME issue I've been having. The company sent me out a 24-pin DME for my 28-pin 1988 non-S, and the car hasn't been running well and failed emissions because of it.

They are trying to find an 88 non-S box, but obviously they are somewhat rare. I imagine an 89 "S" box would be less rare, so I wonder if that DME (with 28-pins) is the same as the 88 non-S, but with different chips? Meaning, could I have them send me the S unit, and put my non-S Guru chip in (since it has the right number of pins), and things would be gravy? I reason that maybe for cost reasons all the 28-pin computers were actually the same, but the chips were different.

My other thread is here:
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/191703-86-24-pin-dme-in-88-28-pin-car.html

fast951

Yes you can interchange boxes as long as you use the correct chip.

Tom M'Guinn

You say in your other thread that you have GURU chips (presumably 24 pin?) installed in the new box. Do these chips have the same maps as the chips that were in your 28 pin fried DME? I gave GURU chips a shot in my car, and Danno took a couple stabs at custom programming them for me, and I noticed a big variation between chips. Also, did you check the Fuel Quality Selector switch on the replacement box, to make sure it was set as needed?

Skwerl

Yeah, the FQS is set correctly. And the car runs poorly with the chips that came with the DME they sent me, and the Guru ones for it. I assumed that the 24-pin chips would be mapped correctly for the 24-pin box, so I tried them. In any case, I think once this is resolved I'm going to get the Vitesse MAF, to make sure my fried DME wasn't related to the Guru chips to begin with. (I doubt it, since I had them for a couple years, but who knows.)

Lorenfb

"They are trying to find an 88 non-S box, but obviously they are somewhat rare. I imagine an 89 "S" box would be less rare, so I wonder if that DME (with 28-pins) is the same as the 88 non-S, but with different chips?"

Per my my Porsche wiring diagrams for a 944S ('87 & '90), the DME is a 55 pin box.
The design is totally different than the early 944 & 944 Turbo (35 pin box).
The early DMEs used 32K or 64K EPROMs (early 911 3.2 16K) which were selected
by jumpers. The later box (55 pins) used 256K EPROMs. Your car should have the
Bosch 077 or 086 for a non-turbo or the 075 box if it's a turbo. Check out this
web site for other possible Bosch numbers ( www.systemsc.com/Parts.htm ).

Remember:

1. 24 pin EPROMs are 16K (2K X 8) or 32K (4K X 8)
2. 28 pin EPROMs are 64K (8K X 8), 128 (16K X 8) 256K (32K X 8),
512K (64K X 8), etc.

Additional Note:

A 24 pin EPROM DME is capable of being modified to use a 28 pin EPROM by changing the jumpers.

fast951

Loren, he's talking about the 951S vs951 non-S!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Lorenfb

" imagine an 89 "S" box would be less rare, so I wonder if that DME (with 28-pins) is the same as the 88 non-S,"

Please read what the guy wrote! It would be helpful to all to provide part numbers
in the future.

Tomas L

Loren, have you checked which forum you're in?
It's interesting to see that your answers always show the same confidence and a bad attitude regardless if they are wrong or right....
You do a great job promoting your company...

special tool

I already told him that this isn't the Boxster ("do I have a dry sump?????") forum, nor is it the 3.2 (Oh my God, how many shims go on the inside of this thing???") forum - but he doesn't listen.

Lorenfb

More info:

The later 944 DMEs that use the 64K EPROM execute the u-p code from the within the EPROM.
ALL the 944 DME boxes (later ones, & not 944S) are interchangeable with the proper jumper settings.

Just have to love this forum. A lot of "zeros" with no real contributions, just slams!
I'd think you'd expect more from a Rennlist forum, but maybe not.

TT

Lorenfb == Clueless

Tomas L

That would explain why he's talking about 944 N/A and 944S in the 944 turbo and turbo-S forum.

Tom M'Guinn

For what is it worth, there was no 944S in 1989. They built the 944, 944S2 and 944 Turbo that year. When people familiar with these cars refer to the '89 "S" they mean the '89 944 turbo -- since it is essentially the same as the '88 Turbo S car.

Skwerl

To clarify what I was intending to say, most people here have it right:

I have an 88 non S, which came with a 28-pin EPROM

I have a box from presumeably an 86 (since they had the highest production numbers, right?) 24-pin EPROM

I was wondering if an 89 DME (I put the "S" in quotes because it's really a turbo S, but not designated as such), also having 28-pin EPROM, is the same DME except for the chip

...meaning, at the Porsche factory in late 1988 the only difference between the S DME and the non-S DME if you opened it up was the different chip.

...meaning I could have this company (Vertex), who says they're having trouble finding an 88 non-S DME, send me an 89 DME (which I figure is more common) and I could just put in my old 28-pin non-S chip. I reckon the DMEs could be the same except the chip, but I don't know.

Thanks, everyone, for the replies.

(Also, converting the 24-pin to a 28-pin is a possibility, but I don't know where to find the jumper settings for the 28-pin unit to change on the 24-pin.)

944Fest (aka Dan P)

I have an early turbo box with early turbo aftermarket chips that I interchange with my turbo S box with modified turbo S chips in my 89 944 turbo (S) without any problems.

Ya got that?

PS.. to skwerl, please us the wording "turbo-S" and "turbo non-S" to avoid further confusing site sponsors who call helpful posters "zeros"