Air-21

I currently run a RacePak IQ3 dash in my 996 GT3 racecar for data collection and a consolidated easy to read display. One bit on information that I have been missing out on is the brake and gas pedal input pressure, due to the complicity of setting up the capture mechanisms. RacePak just announced they will have a universal OBDII module that will plug directly into the IQ3 dash for data collection but it is not cheap. So my question is, whether or not it is even possible to capture brake and gas pedal pressure from the GT3 OBDII port?

LVDell

You cannot as far as I know. To capture throttle position sensor you will need to access the DME on the rear shelf. For brake, most just use a tap into the brake light and have it report as an on or off function not pressure. For that, you might need to install a brake pedal potentiometer.

Hopefully others that have done this will chime in.

ninerguru

Just for kicks I googled CDR (crash data recorders) Plenty of info from SAE, Bosch, etc. Most of them record % of throttle, but only if brakes are active or not at time of impact. Looks like they have readers to extract data by plugging into the OBD2 (dlc connector) for field investigations... http://www.cdr-system.com/ http://www.nhtsa.gov/DOT/NHTSA/NRD/M...rch/810935.pdf

wapita

Did you ever find the answer for this? From what I've read you can get these from the OBDII port:

ECU_1 P911_RPM RPM
ECU_2 P911_SPEED1 VEHICLE SPEED
ECU_3 P911_PPS THROTTLE PEDAL POSITION
ECU_4 P911_ENGINEMOMENT TORQUE VALUE
ECU_5 P911_WATERTEMP WATER TEMPERATURE
ECU_6 P911_AIRTEMP INTAKE AIR POSITION
ECU_7 P911_BRAKE BRAKE SENSOR ON/OFF

FTS

Is the ODBII bridge now available from RacePak? I thought it wasn't ready still, waiting on part to assemble. But I believe your list above is accurate, but we'll only know when we actually get it on our hands I believe.

wapita

Seems like it might be although they don't have it on their price list:

http://www.racepak.com/Components/OBDII_signup.php

gvtesse

I've been searching around on how to hook up a LED to the dash to go on when I depress the brake pedal. Were can I tap into the brake light?

Thanks.

LVDell

Back in the rear tail lamp assembly.

ninerguru

I think it will be easier to tap directly from the brake switch... That is the way you hook up a brake controller for a trailer...

gvtesse

Do you happen to have a diagram/picture of where that is?

Serge944

You can't capture brake pressure through OBD2. You have to have a stand alone accelerometer to capture deceleration rates. If you hook into the brake pedal switch, you only have "on/off" information.

OBD2 does output throttle position by the voltage from the potentiometer at the gas pedal. Interestingly enough, my car only does "99.7%" throttle with the pedal to the floor.

gvtesse

At the moment I am only looking for on/off to trigger a light on the dash.

ninerguru

Looking at the schematics from a 2000 996, looks like terminal 1 on the brake switch, black wire, has 12+ always. Terminal 2, black/orange wire gets powered at brake application. You can pierce the wire using a needle and use a volt meter to check for voltage on brake application... Hope this helps...

gvtesse

Is the brake switch #18 in this pic?

ninerguru

Yep, that looks like it. 17 is most likely the clutch interlock for starting. It should be located right in line with the pedal and should click as the pedal is depressed closing the switch an sending power to the tail lights...