924Board.org

McGyver · Posted: Sat Jan 02, 2010 9:29 am Post subject:

There's no EPROM or any memory inside. DITC unit even don't have any microprocessor. Map is provided by logical gates which are controlled by input signals. In manual they wrote DITC unit can operate without almost all input signals - but it will not work properly. Only Timing from flywhell is needed to run the engine.
For example temperature sensor is just a Thermocouple which gives some small voltage, which could be amplified and could be used to activate one of gates.
But in manual that temperature sensor looks like thermo-resistor which resistance is changeing depends on temperature. So in this case the voltage can be change by connected resistance and that could activate/deactivate proper gates.
Throttle swich connect something to ground. So it gives only digital signal "0" or "1" which works with... yes

some logical gate/gates.

Gates need from +3V, +18V power supply so 12V from battery will be enought. So most of that resistors/capacitors, diodes and... few transistors are needed only to ensure proper voltage levels for gates to work... and to provide proper digital levels - which depends on power supply voltage level.
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931 82' - 5000km after full engine rebuild

SOLD: 924 81' N/A- with turbo gearbox "dogleg" - great but mysterious car

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flosho · Posted: Sat Jan 02, 2010 2:38 pm Post subject:

Wow this is all soo far over my head but sounds soo cool.

Its an old system so we should be able to crack it and adjust it.
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Rich H · Posted: Sat Jan 02, 2010 7:32 pm Post subject:

So all we really need is the logic table and a simple microprocessor could replace it.
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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

michal928 · Joined: 10 Sep 2008 Posts: 41 Location: Warsaw

I can copy a 937 DITC based on S2 hardware. Advance of the ignition is adjusted only by replace resistances and added a little circuit board on the motherboard. Ignition map can be adjusted without any problem. The only one problem is to have an original computer from CGT to copy this little circuit board, find and measure those adjusted resistances and do a copy on S2 ditc. We can add an extra switch to replacing those adjusting resistances on the fly and modify engine power in the road

morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

That sounds like the fastest solution...very interesting.

Forgive my skepticism but are you 100% sure you are up to the job and know what you are doing when you say that you can identify and change the parts on the S2 DITC to match the CGT functions?

we have both S2 and CGT boxes available for inspection.
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michal928 · Joined: 10 Sep 2008 Posts: 41 Location: Warsaw

It is the fastest and most easy solution. S2 ditc is cheap.
I have 931 `81 Euro specification and DITC in my car. When i dissasembled the unit and compared to photo of the 937 unit they almost identical. The only difference between them is added a little circuit board on 937 (i think it is logical circuit easy to buy but i can not see sign of the IC on the photos) and other value of the several resistors. The motherboard is identical. Do a copy it is not a problem - i am electronics engineer.
But i have question - CGT have a forged pistons, S2 have only cast pistons. Is not that a problem?

924guy · Posted: Sat Jan 02, 2010 11:56 pm Post subject:

okay, so if im reading this right, we (ok, not me, but some of you micro wizards) should be able to make an input box that reads all the signals, and translate that through a modern processor to make the car run. and if thats true, its only a a step away from from integrating a storage platform and usb port to read and adjust the data via a pc...

even a solid state, switchable, three level "map" would be awesome. with normal , sport, and 911 eater modes

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morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

until now we have two options:

1 . modify the 931 S2 DITC to a 937 unit.
2 . use an MS unit or any unit and modify it to create a bolt on product.

The 931 pistons will be just fine ! there are people runing 1 bar or more on these pistons without problems.
I think everybody that will use a CGT DITC will also have an intercooler installed or at least run on stock boost.
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gegge · Joined: 27 Jul 2007 Posts: 1124 Location: Sweden

I am VERY interested in an adjustable 931 DITC. If you are able to make a print of the circuitboard with all components including the ones that should be replaced with variable ones I´m willing to support the case financially. I´ve got an two DITC in the garage if you need photos; one UK and one German model.
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McGyver · Posted: Sun Jan 03, 2010 4:19 am Post subject:

I should be able to make a print of the circuitboard but I need detailed photos from DITC unit from booth sides. And at least infos what is writen on capacitors/transistors... something what can't be seen from photos.
I want to make some logic table from that logic gates but I have to know exactly how they connected. All datasheets can be easly found for all IC's so it's not to hard to understand how it works.
Only inputs could be interesting becouse they should give digital signals - I'm not sure yet.
So anyone who can make good photos of DITC unit please send me it on my e-mail. PM me if you have those.

Best from German model

UK were a little different!!
_________________
931 82' - 5000km after full engine rebuild

SOLD: 924 81' N/A- with turbo gearbox "dogleg" - great but mysterious car

www.mauser98k.internetdsl.pl - if someone like german rifles (English version avalible)

morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

michal928 · Joined: 10 Sep 2008 Posts: 41 Location: Warsaw

In my last 924 i had a fuel injection and ignition controlled by megasquirt, wide band lambda controller, switching maps... I bought a new computer but i do not installed in my turbo because i am scared to destroy my engine. I do not recommend the megasquirt for those who do have not many information and do have not much time..
DITC is complete solution without any problems, do not need to be tuned - only just copy ready solution which working for 100% based on the same computer.
Does anyone tested the torque and power before mounting DITC from 937 and after do this on the same dyno in the same day?

McGyver · Posted: Sun Jan 03, 2010 6:36 am Post subject:

I think the best will be upgrade 931 unit to 937 witch some kind of swich or make a DITC controled by simple microprocessor.
Maybe DITC unit from 931 is quite cheap, but if we can make a full working copy and upgrade it to 937 that will be much help for all who wants upgrade they 931 DITC and worry about original computer.

I want to make a full digital documentation of DITC unit containing wiring schemes, logical tables and all possible info we can get. So even if someone want's to build it from nothing that will be possible.

And now I make a little upgrade of previous image:

If I have more time I could upgrade that image with next elements and I hope with wiring

but... I still wait for any more details photos.

As I heard DITC unit from Germany have a little different map than UK unit but I can't confirm that. Definitely USA unit is different than Euro spec.
_________________
931 82' - 5000km after full engine rebuild

SOLD: 924 81' N/A- with turbo gearbox "dogleg" - great but mysterious car

www.mauser98k.internetdsl.pl - if someone like german rifles (English version avalible)

morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

An easy solution would be to buy an extra 931 DITC, upgrade it to 937 specs and install a switch system that would allow switching between the two control units.
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michal928 · Joined: 10 Sep 2008 Posts: 41 Location: Warsaw

morghen - i think it is possible to do.
Together with McGuyver we will try to do the schematic of the S2 DITC for understand how it works. We will be need the best possible photos in the highest resolution of the 937 DITC or better will be to have this computer "in hand" but with this it will be hard...(It is nonsens to buy a computer and do a copy - in poland we have only few known 931)