M84 Integration with Porsche 993 ABS Module

Discussion and support for MoTeC's previous generation of entry level ECUs

M84 Integration with Porsche 993 ABS Module

Postby Kowalski on Thu Apr 02, 2020 9:11 am

Hello,

I am finishing up a 1995 Porsche 993 track car with an M84 ECU, two PDM15s, Central Informer to run the gauges and the OEM Bosch ABS controller with ABD. Almost everything is wired, online and working except I do not have a TVS signal to send to the ABS module. I am wondering if someone is familiar with the OEM Porsche setup and could share with me if the TVS is straight analog voltage or a PWM signal? I have seen TVS referenced as a PWM signal but cannot find any specs for it. Also, if TVS is a PWM signal, can the M84 be programmed to output this?

It is the Throttle Valve Info Signal from Pin 52 on the Motronics DME to Pin 47 on the Bosch ABS ECU. I do not have access to a factory setup to test.

Thank you for any and all help!
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Re: M84 Integration with Porsche 993 ABS Module

Postby Kowalski on Fri Apr 03, 2020 1:23 pm

I figured this out, thank you all for reading my post. In case someone is curious, it is a PWM signal.

As measured on the bench with a 1995 993 Porsche DME ECU:

TPS TVS Values.JPG
TPS TVS Values.JPG (18.09 KiB) Viewed 6512 times

Values were measured at tip in and tip out before a code sets.
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Re: M84 Integration with Porsche 993 ABS Module

Postby rsscotty on Sat Apr 04, 2020 5:14 am

So how did you configure the ECU to mimic this signal.
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Re: M84 Integration with Porsche 993 ABS Module

Postby Kowalski on Sun Apr 05, 2020 6:56 am

I did not have any available Auxiliary Outputs in the M84 (all 8 are used and it may not even be able to do it correctly) so I put together a 0 to 10 VDC driver circuit controlled by an Arduino with a little code. The M84 TPS signal voltage provides the input to the Arduino.
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Re: M84 Integration with Porsche 993 ABS Module

Postby sardengineering on Fri Apr 24, 2020 1:52 am

Thanks very much for sharing your solution and your findings on this project, I'm sure it'll be of great value to the members here.

Cheers!
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Re: M84 Integration with Porsche 993 ABS Module

Postby Kein Ersatz on Sat May 29, 2021 12:47 am

Thanks for sharing, as serendipity would have it, I am also doing a MoTec M84 swap-out in my '97 Porsche 993 [MFI-DI DME M5.2 NA]. Doing a 4.0 ITB engine build for track duty, but the cabin interior is still in place (RS like) with all the Central Informer (CI) dashboard waring lights. Pulling the old DME ECU and going with an M84, I have "spliced" the Motec into the X 4/1 & X 4/2 harness plugs under the driver seat (LHD) to replicate some of the old DME ECU feeds to the remaining OEM systems. The 3 missing connections (so far) are Belt Sensor alarm light, IMMO alarm light, and ADB alarm (not the information light) light.

Fixing the Belt Sensor alarm light is a simple fused jumper in X 4/2 (pin 14 & 3).

Fixing the IMMO alarm light blinking is a topic of another day / thread.

Fixing the ADB brings me here to this thread.

Missing the TPS from the MoTec I was thinking only affected the ADB function, but not the ABS function. The ADB was not a concern till now (except for the dash light/CI), but now I am wondering if the ABS is also now not operating properly. Either way (ADB light or ADB and ABS fail), I would be interested in a solid fix.

I am familiar with Raspberry Pi boards, but have not worked with Arduino boards. Would you be willing to share more details on your DIY solution or would you be interested in producing and selling a duplicate?

Image

AUTOMATIC BRAKE DIFFERENTIAL (ADB)

Overview:

The 993 offers an exclusive Automatic Brake Differential (ABD) traction management system as an option on the Carrera and as standard equipment on the Carrera 4. ABD works as an extension of the ABS 5 brake system. When a rear wheel spins under acceleration, the control system automatically applies brake pressure only at that wheel. This diverts engine torque to the wheel with more traction, making it easier to start from a standstill under slippery conditions. Above 44 mph, the system becomes inactive. ABD activation is communicated to the driver by an indicator light on the dash. On the six-speed Carrera and Carrera 4, the limited slip differential includes Porsche's ABD traction system. For Tiptronic-equipped 911 Carreras, the ABD traction system without the conventional locking differential is available as an option.

ADB Benefits:

The ABD system serves primarily as a traction aid in starting on slippery surfaces. Porsche's ABD is different from conventional traction control systems as it does not reduce engine power. Driving with ABD is different from driving with a conventional differential. With more than enough engine torque available, the system will sense wheel spin and apply rear wheel brakes as needed to provide the maximum amount of traction, reducing the force at the tire contact patch to the limit of what the surface will sustain.
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