GM DIS Pinout

[cammmy]

Hi All

Working on an MS3/X install for a '98 Lotus Esprit GT3 which has GM DIS from factory. I'm currently working on a table to allow me to cut off the standard factory harness plugs and use the MS DB37's. I've done most of it but am stuck at the DIS module. The factory wiring diagram tells me which DIS wire goes to what pin in the standard plugs, but it doesn't tell me their function. Is anyone able to point me to a pinout for the DIS module? I've tried using the documentation below, but it doesn't seem to match what I have:

http://www.megamanual.com/ms2/GM_DIS.htm

This is what I was able to gather from the above

DIS Function MS3/X DB37
E SpkA 14
B SpkB 33
G Sensor GND MS3 DB37 - 7
R Tach In MS3 DB37 - 24

This doesn't seem to match what I have though. Here are the plugs going into my module:




I believe the plug on the right with the green and black wires are +12v and Ground.

This is what I was able to get from the factory wiring diagram

Pin Function
J2-B10 Engine Management Splice K, Direct Ignition Module (2B)
J4-D19 Direct Ignition Module (6F)
J4-D13 Direct Ignition Module (6E)
J3-C3 Direct Ignition Module (6D)
J3-C9 Direct Ignition Module (6C)
J3-C11 Direct Ignition Module (6B)

Any help here would be greatly appreciated.

[cammmy]

Hi All, hopefully some useful info here!

Apparently the DIS module is Lotus specific, but there is a compatible Isuzu part which I've managed to find a pinout for:

Airtex 6H1131

http://www.airtexve.com/custom_searches ... tno=6H1131

Looking at the above,

A Tach
B 1x output
C EST input MS3 DB37 - 36
D Bypass MS3/X DB37 - 33
E Ref. high MS3 DB37 - 24
F Ref. Low MS3 DB37 - 7

Does the above make sense? I've been using the jim stim kits to test and have set GM bypass on SpkB.

So C is used by the ECU to tell DIS how much advance to use, D is to tell DIS to bypass what the ECU is telling it during cranking, E is engine speed to the ECU and F is ground? Does I need anything else? Do I need to do anything with A or B?

Thanks
Cam

[cammmy]

I believe A just goes straight to the tacho, so nothing to do there.

Apparently B is a sync pulse. The DIS documentation doesn't mention doing anything with that? It just says to send the Reference high to pin 24 on the MS3. Will the MS get all the info it needs from Ref. high?

Thanks

[jsmcortina]

From the look of it, that pin B 'sync' output gives you the cam signal and could be used to run sequential.

James

[cammmy]

Hi James

I've jut had this response from a Lotus forum:

"The MS3 will only need the sync pulse if it's doing semi-sequential injector firing like the Esprit (it cannot do full sequential without no. 1 cylinder identification and this isn't supported by the stock Esprit system)."

I'll go back through the documentation tonight and see whether semi-sequential can be used with DIS.

Ta
Cam

[jsmcortina]

Without the cam-sync you are untimed batch fire only. With the sync pulse you can do semi sequential or full sequential.

James

[cammmy]

Brilliant, thanks. So does this make sense?:

DIS MS DB37
A Tach N/A
B 1x output MS3/X DB37 - 32
C EST input MS3 DB37 - 36
D Bypass MS3/X DB37 - 33
E Ref. high MS3 DB37 - 24
F Ref. Low MS3 DB37 - 7

A sync pulse would need to be 1x pulse every 720 degrees for full sequential right? If the sync pulse is every 360 degrees, this will still support semi-sequential?

Thanks again.
Cam

[racingmini_mtl]

A sync pulse would need to be 1x pulse every 720 degrees for full sequential right? If the sync pulse is every 360 degrees, this will still support semi-sequential?

Yes and yes.

Jean

[cammmy]

Great, thanks. Are you able to see anything obviously wrong with my pin mapping?

[cammmy]

Hi, hopefully the last question for this. With regards to the Ref and sync signals, When working with DIS, MS expects a distributor like signal; would this be once per revolution or once per ignition event?

if the Sync signal is once every 360 degrees and the Ref signal is once every 180, Would I connect these as follows?:

Ref. high MS3 DB37 - MS3/X - 32
1x output (Sync) - MS3 - 24

or

Ref. high MS3 DB37 - MS3 - 24
1x output (Sync) - MS3/X - 32

Thanks

[cammmy]

Hi, I've been doing some further reading. It seems semi-sequential isn't an option with basic trigger.

I've been reading/searching but I'm still a wee bit mystified by the options. Would someone be able to point me in the right direction? I'm thinking I would be connecting the Ref. high output to pin 24 on the MS3? Any advice on which injection settings to use (batch/sequenced batch? Number of injections per cycle?).

Will the 1x output now be redundant?

Ta
Cam