MySR71

For water temp, Ben provided some data and I fit a curve to it. Below about 120 degF, it gives an incorrect reading. The temp circuit seems to change around this temp.

If you prefer a function, it is this:

Temp (degF) = 0.0365477458944952*V^6 - 1.37691779802641*V^5 + 14.3256285124391*V^4 - 69.4597440685648*V^3 + 179.707756800085*V^2 - 287.449559849111*V + 414.418077041844

Where V it voltage and the output is the temperature in degF.

I'd give this a try.

Hi Volts Z06

That should be all I need. I actually used only two data points to calculate oil temp and other than reading 3 degrees F when temps are below 144, it seems to be pretty accurate.

Thank you!

mattastick

To me, the more useful thing to test with wheel speeds is brake pads, and how they interface with the ABS over bumps. Certain pads are known to have better or worse release characteristics than other pads, but for cars without EBD (pre-01 C5s), this is also useful in getting the brake balance sorted out.

I just got my RaceCapture Pro Mk3, and I think this will be a pretty good option for tapping into the factory sensors on a C5. Max sampling rates of each analog channel is 1kHz, and it's configurable for each channel.

My plans are to use the gyros in the RCP rather than the yaw gyro on the car, but I'm going to tap steering angle (and derive the channel for steering rate), throttle position, brake pressure, shock position (F55 sensors), and wheel speeds. This is primarily for autocross, where we're allowed to run 2 drivers in the same car, and I'm really curious to see what the difference is between drivers for brake pressure and steering input.

MySR71

Hi Volts Z06

Another question for those of you that are tapping into stock sensors. Are using a pull up resistor or allowing the PCM's pull up resistor to provide voltage? I'm running into some issues and think my problem is that I'm using a pull up resistor bridged between the MXG's 5v output and the return (or pins 1-4 for those of you who are familiar).

MySR71

I am not using a pull up resistor. I'm only splicing into the sensor's output wire and connecting that to the break out box in my data system. I am telling the software not to use a pull up resistor. Sometimes, I also splice into the sensor's ground wire and also connect that the break out box. I let the car supply the sensor's 5 volts as it did when stock.

I do, however, have to turn on the data system before turning the car's key. Otherwise, the car will set codes. Similarly, I turn off the car, then the data system. So the data system is first on, last off.

If you are still talking about the water temp, note that it will read a very wrong number until the temp gets over around 120 degF.

Hi Volts Z06

Thanks for the reply. What system are you using? I find my Aim MXG automatically reboots if I turn it on before starting. I also think my problem is that I'm trying to use the pull up resistor and I might have the polarity reversed. It was working correctly when the ignition was off and then when I started the car leading me to belive what you said is true....all I have to do is read the output voltage of the sensor.

MySR71

I have a Racepak G2X Pro. For power, it is hardwired in to a power source that does not turn off during engine start. Yup, just look at the output voltage of the sensor and use a calibration to convert it to relevant units.

PS It MIGHT work ok if you turn on the data system immediately after starting the car. Don't wait more than a second or two.

RX-Ben

Right, if you are using the OEM temp sensor(s) - the PCM provides a pull-up resistor so you can just tap into the wire - you do not want to introduce a 2nd pull-up.

Hi Volts Z06

Ben, when you picked up sensors on Mark's car, did you use the ground connection or simply tap only one wire since the logger already has a ground connection?

RX-Ben

one wire. The logger will use it's ground (which should go to a frame rail). Not ideal (theoretically), but plenty good for temp sensors.

Hi Volts Z06

Thanks Ben. I made this WAY too complicated!

Hi Volts Z06

This seems to be the right thread for my problem so here it goes:

Anyone every had a problem when tapping into the TPS sensor on a C5? I tapped into that with my MXG and everything was fine. After the second session on track, I lost my throttle pedal and the engine ran at idle until I disconnected the MXG from the sensor. Everything was fine after. While I didn't pull any codes (since the problem was fixed) I'm guessing that the slight bit of resistance from the MXG caused the TPS1 and TPS2 sensors (and possibly APP1 sensor) to have a slight imbalance triggering a code.

MySR71

The only time I've every had trouble on my 2002 was when I turned on the ignition prior to turning on the data system. Then fault codes are generated after a very short time (seconds) although I'm not sure if it is because the APP, steering wheel sensor, or brake pressure sensor. The APP channel that I'm recording is the one which goes from a low voltage at zero throttle and increases in voltage at WOT. I haven't tried the other one.

PS I've spliced into the sensor's wiring under the dash.

Hi Volts Z06

Throwing a code isn't what concerned me.....limp mode on the front straight of NJMP was the problem. Funny thing is I made about 4 laps before it happened.

GO_BLUE_VETTES

So did you determine a reliable fix? Did you use a larger pull-up resistor? Or switch to a different sensor (i.e. The APP instead of the TPS)?

I have an MXG as well and want to do the same thing.

Hi Volts Z06

No....I had an engine fire later that day due to a bad o-ring on my dry sump system so I'm still rebuilding the car. Was hoping to get some input here before trying again.

GO_BLUE_VETTES

How exactly did you connect the MXG? which connector to adapt to a AIM 719 connector did you use? what pullup sensor if any?

MySR71

I have not had mine go into limp mode either.

Hi Volts Z06

I purchased patch cords from Binder directly and just used a multimeter to figure out the pinouts. From there you only are hooking directly to the sensor output and reading the 0 to 5v signal. There is no pull-up resistor required. Again, I ended up in limp mode after tying into TPS2 so I'm trying to see how others have done it.