Changing '95 993 Motor to OBD2 brain? Doable? Options

[SirAndy]

My '95 993 Motor is a pre-varioram OBD1 Motor and i have been toying with the idea of updating it to OBD2.

There was, for a short time, a OBD2 brain available for the (still aircooled) 993 starting in '96 with the varioram version of the motor.

It is my understanding that besides the tubes inside the intake, the two motors are pretty much identical.

I wonder if i could get a later brain and harness and make it work with my engine.
Is there anyone out there who has tried this?
(IMG:style_emoticons/default/idea.gif) Andy

[Cap'n Krusty]

From what OBD2 stuff I deal with, I have a couple of thoughts. If the system you're controlling is missing components, you may have insurmountable issues. If you're expecting full OBD2 performance out of a 1996 unit, you're NOT gonna get it. It was only slightly more sophisticated than the OBD1 unit it replaced, and lacks a LOT of functions. If you were to change the entire induction/exhaust system to go with the ECU, and you had all the other monitoring components in your car, you might have SOME of the functions you seek, but they might also be pretty basic. Later OBD2, which is pretty well developed after 12-13 years, has hundreds, probably even thousands, of functions, and would be ideal for your use. Remember, however, that there's no such thing as a free puppy, and this puppy could end up costing you a TON.

The Cap'n

[ghuff]

From what OBD2 stuff I deal with, I have a couple of thoughts. If the system you're controlling is missing components, you may have insurmountable issues. If you're expecting full OBD2 performance out of a 1996 unit, you're NOT gonna get it. It was only slightly more sophisticated than the OBD1 unit it replaced, and lacks a LOT of functions. If you were to change the entire induction/exhaust system to go with the ECU, and you had all the other monitoring components in your car, you might have SOME of the functions you seek, but they might also be pretty basic. Later OBD2, which is pretty well developed after 12-13 years, has hundreds, probably even thousands, of functions, and would be ideal for your use. Remember, however, that there's no such thing as a free puppy, and this puppy could end up costing you a TON.

The Cap'n

Yes.

Most OBDII units that allow you to monitor what is going on do not support anything that the OP mentioned.

you might be able to see O2, coolant temp, throttle position, generic OBDII stuff. Like one of the scan tools that you can plug in and monitor your mileage etc.


I had explored the most that a Snap-ON Modis unit would do with plain jane OBDII and was left very unimpressed.

What you are looking for, you need standalone. Forget error codes, take control of the car and know what it is all doing 100% of the time.

[SirAndy]

What you are looking for, you need standalone. Forget error codes, take control of the car and know what it is all doing 100% of the time.

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Are we reading the same posts?
(IMG:style_emoticons/default/huh.gif) Andy

[ghuff]

What you are looking for, you need standalone. Forget error codes, take control of the car and know what it is all doing 100% of the time.

(IMG:style_emoticons/default/confused24.gif)

Are we reading the same posts?
(IMG:style_emoticons/default/huh.gif) Andy

Yes.

Again you want to know what is going on 100% you will need standalone. OBDII generic data is just not enough. You may or may not get what you want, it really depends on how Porsche adhered to OBD2.

http://www.greddy.com/featured/104touch060909.pdf

Look at the supported functions, and breakdown of that device. The most you will get is really dependant on the Porsche OBDII and how it adheres to the standard.

There are a plethora of these devices available that all do the same thing.

If you want to test it, find a shop with a Snap-ON modis and go into standard OBD2 mode and see exactly what you can see on an OBD2 car of someone you know.

The modis is one of the best.

The standard OBD2 values I could monitor on my CANBUS 2001 GTi with drive by wire was sorely lacking. Coolant temp, o2 value (worthless unless you have a factory wideband) etc.

I imagine a 1996 OBDII being much worse or equal.

100% not worth the effort. Now the internal functions and KWP(K wire protocol requiring a VAG-COM or a vag 50,000$ tool) accesible values I could monitor were worthwhile. Per cylinder knock, per cylinder trims for timing. etc.



OBD2 is not just OBD2.....

OBD-II Diagnostic connector
Connector

The OBD-II specification provides for a standardized hardware interface—the female 16-pin (2x8) J1962 connector. Unlike the OBD-I connector, which was sometimes found under the hood of the vehicle, the OBD-II connector is nearly always located on the driver's side of the passenger compartment near the center console. SAE J1962 defines the pinout of the connector as:

1. -
2. Bus positive Line of SAE-J1850 PWM and SAE-1850 VPW
3. Ford DCL(+) Argentina, Brazil (pre OBD-II) 1997-2000, Usa, Europe, etc.
4. Chassis ground
5. Signal ground
6. CAN high (ISO 15765-4 and SAE-J2284)
7. K line of ISO 9141-2 and ISO 14230-4
8. -
9. -
10. Bus negative Line of SAE-J1850 PWM only (not SAE-1850 VPW)
11. Ford DCL(-) Argentina, Brazil (pre OBD-II) 1997-2000, Usa, Europe, etc.
12. -
13. -
14. CAN low (ISO 15765-4 and SAE-J2284)
15. L line of ISO 9141-2 and ISO 14230-4
16. Battery voltage

The assignment of unspecified pins is left to the vehicle manufacturer's discretion.

[edit] Signal protocols

There are five signalling protocols currently in use with the OBD-II interface. Any given vehicle will likely only implement one of the protocols. Often it is possible to make an educated guess about the protocol in use based on which pins are present on the J1962 connector:

* SAE J1850 PWM (pulse-width modulation - 41.6 kbaud, standard of the Ford Motor Company)
o pin 2: Bus+
o pin 10: Bus–
o High voltage is +5 V
o Message length is restricted to 12 bytes, including CRC
o Employs a multi-master arbitration scheme called 'Carrier Sense Multiple Access with Non-Destructive Arbitration' (CSMA/NDA)
* SAE J1850 VPW (variable pulse width - 10.4/41.6 kbaud, standard of General Motors)
o pin 2: Bus+
o Bus idles low
o High voltage is +7 V
o Decision point is +3.5 V
o Message length is restricted to 12 bytes, including CRC
o Employs CSMA/NDA
* ISO 9141-2. This protocol has a data rate of 10.4 kbaud, and is similar to RS-232. ISO 9141-2 is primarily used in Chrysler, European, and Asian vehicles.
o pin 7: K-line
o pin 15: L-line (optional)
o UART signaling (though not RS-232 voltage levels)
o K-line idles high
o High voltage is Vbatt
o Message length is restricted to 12 bytes, including CRC
* ISO 14230 KWP2000 (Keyword Protocol 2000)
o pin 7: K-line
o pin 15: L-line (optional)
o Physical layer identical to ISO 9141-2
o Data rate 1.2 to 10.4 kbaud
o Message may contain up to 255 bytes in the data field
* ISO 15765 CAN (250 kbit/s or 500 kbit/s). The CAN protocol is a popular standard outside of the US automotive industry and is making significant in-roads into the OBD-II market share. By 2008, all vehicles sold in the US will be required to implement CAN, thus eliminating the ambiguity of the existing five signalling protocols.
o pin 6: CAN High
o pin 14: CAN Low

Note that pins 4 (battery ground) and 16 (battery positive) are present in all configurations. Also, ISO 9141 and ISO 14230 use the same pinout, thus the connector shape does not distinguish between the two.

Perhaps I can clarify it more for you if need be?

(IMG:style_emoticons/default/confused24.gif)

(IMG:style_emoticons/default/shades.gif)

[SirAndy]

Perhaps I can clarify it more for you if need be?

Well, you did just clarify that you didn't get what i want at all. Which is why i asked if you had actually read my posts. So, thanks for clearing that up.

Like i stated above, i already have the data logger. It connects to OBD2. It can read Porsche specific data.

But the real interest lies in the fact that it can transmit data wireless in realtime and has build in GPS and can measure G-Force, acceleration and braking.

The actual data coming from the engine is just a added bonus. So no, i don't "want to know what is going on 100%" ...
(IMG:style_emoticons/default/driving.gif) Andy

PS: Nice copy & paste. Is that from Wikipedia?