I made an OBD1 to serial datalogging cable with some instructions off of dsmtuners.com. This cablet hooks into the serial port on the back of my car PC's docking station and connects to the diag port of my car's ECU. The only difference I made to the cable was switch pins 2 and 3 as the design on the website is geared for a Palm Pilot
http://www.dsmtuners.com/forums/showthread.php?threadid=203316



Just need one 10K resistor and one 1N914 diode, plus the serial female RS232 connector


I actually had to hacksaw the back of the connector to find something to solder on to...I honestly thought this was too scetchy to work.






I ended up replacing the alligator clips with female connectors...just wanted the clips to test to make sure it worked.

The transmit wire comes off of serial pin 3 and connects to pin 1 on the ECU diag port. Pin 5 on the serial splits at the end and shorts pins 10 and 12 on the ECU diag, allowing for serial communication on pin 1.[/img]

I used the TMO datalogging software that is written for 91-93 Stealths/3000GTs. This is a Windows app and is mainly navigated by single left-clicks...perfect for the touchscreen.



Launch the app and press connect


The collect data, DRB2, and Review options work correctly, the Describe Car option does not work and the makers of this software folded awhile back so that's just for show


Clicking DRB2 data brings up a window with several important tabs. These tabs show you live stats on most of the sensors that feed into the ECU. Most tabs also let you switch back between voltage and value readings.


This is when the motor is off, but the power to the car is on...notice no air flow value and the battery reading around 12v


Here's where the fun begins, data gathering. This is accomplished by selecting "Collect Data" from the main menu


The data select allows you to choose one or multiple values and capture data based on those values.


This particular capture will monitor engine knock in relation to engine speed. Time is always the x-axis value in these graphs. This would be a great test to see if the engine is retarding timing because of too many knocks, thus robbing power.


You can barely see the knock count of 1 at around 30 seconds into the capture. This occured around 2150 RPM. Also, noisy valve lifters can trigger the knock sensor, thus inadvertedly cutting power.


One of the handiest features of the tests is that you can save the data in TMOs proprietary file format to be read by the TMO Datalogger, or export the data to a .csv file and work on it in Excel. This is an example of an Oxygen Feedback Trim and Oxygen sensor test I ran.


Finally, you can graph the data in Excel in various ways. Here's the Oxy Trim in relation to time. The oscillations hover around 100%, meaning it's reading a stoich value for the trim data. The oxy trim is used by the ECU to build the actual long-term fuel trim tables that the ECU uses when in a closed loop environment

So now I have a bunch of tests to run and document. This should be a great way of monitoring the health of my car!

I forgot to mention one very powerful tool in "Collect Data" mode. You can build custom triggers based on the variable values to accomplish logging tasks. Say for instance, you wanted to start logging when the Engine RPMS became greater than 4000.00. You could program a trigger to start graphing Engine Knock and Engine RPMS when the trigger value was met. There are tons of combinations available, all of which conform to a certain scenario.

Nice writeup Rob. Thanks for taking the time to put it up for everyone. I'm sure a few passer bys will find this info pretty helpful.

One final note, of a more dubious nature...having this cable hooked on to your ECU and having the ECU in diag mode kills signal to the speedometer and the odometer. So, if you want to keep the miles looking low you can just leave the cable conncted at all times.

— LicenzedToThrill

You can barely see the knock count of 1 at around 30 seconds into the capture. This occured around 2150 RPM. Also, noisy valve lifters can trigger the knock sensor, thus inadvertedly cutting power.

What we in the DSM community like to refer to as "Phantom Knock"

Now rob second step is to get that ECU socketed and get some sort of EMS, so when the tuning is off you can fix it!

None the less great job dude,
good to see someone is able to pull some info off tOOners!

I am heading the palm way my self until i can find an EPROM ECU. Fig that plus the SAFC i shouldnt have too many problems.

By the way on a side note, Fuel line & fittings are crazy expensive!?!

— BLCKOUT92

By the way on a side note, Fuel line & fittings are crazy expensive!?!

Are you in the process now of redoing fuel lines?

Well in the process of upgrading my turbo their were tons of other things that had to change too. One was to change out the stock fuel pressure reg to an adjustable reg. I want to use my stock fuel rail with 650cc injectors so i had to by new -6an end fittings. I spent close to 100 bucks on 2 -6an 90 swivels, 2 unions, 2 plugs, and two strait connectors and seals. The -6an braided steel hose was 40 for 6'!