Dan Wendling

Is the AIM MXL Pista compatible with the C5 ECU CAN interface. The web site lists only the C6 ECUs, but I think I have seen AIMs used in C5's just wondering if they are fully functional?

wallyman424

No, you have to connect the sensors individually in the c5. In the c6, since its canbus, you can connect to the obd port and get all the ECU data.

GO_BLUE_VETTES

When you say "the sensors" do you mean you can connect various C5 sensors through an input block? Or do you mean buy new sensors and connect them?

gkmccready

What Wally said. AiM MXl Pista to C6 is a breeze through the OBD-II port. I have one in my car and it's absolutely perfect. Been thinking of a C5 lately and it'd required doing all sorts of wiring rather than just connections to the CAN bus...

RX-Ben

realistically, you only need to log rpm, tps, brake pressure and steering angle. Similar amount of work for either a C5 or C6.

wallyman424

Typically you have to buy new sensors, because tapping into the existing sensors can cause issues with the ECU.

RX-Ben: its NOT a similar amount of work. W/ the c6, all you do is plug the AIM into the OBD port, and you get ALL of that stuff. W/ the c5 you either have to find your own inputs.

GO_BLUE_VETTES

So at risk of thread hijacking (we've already answered the first question). - We have established that AiM doesn't plug into C5s.

What is a popular option for plug and play data in a C5z?

I want to integrate data (wheel speed, RPM, brake, throttle, steering, etc) with GPS and Video. I was taking a look at AiM, but also others with Traqmate, Video Vbox, etc.

KBlanke

It will not read the C5 ECU, you add what sensors you want. We run this setup in our C5, using oil, and brake pressure, temps (oil, water, trans, and diff) . It does read the RPM from the lead going to the factory tach, it has own sensors for G's, we have the GPS module for speed and lap times.

gkmccready

C5s, and 2005 C6s, don't offer a high-speed data bus capable of moving enough data out of the ECU to the data logger to make a plug'n'play option useful. You could do it but you'd be sampling the data so slowly you'd probably miss interesting stuff. While we keep saying OBD-II port the AiM boxes actually just connect to two wires... the high-speed CAN bus...

RX-Ben

Sorry about that -didn't realize that CAN supported steering angle and brake pressure. Don't you need to know the hex codes to pull the CAN info? Need to add that to install time as well.

gkmccready

It's missing brake pressure, but has almost everything else. And AiM has gone through the trouble of digesting all the GM codes... all you do is connect two wires and say "GM C6 Corvette ECU" in the software...

RX-Ben

Awesome post, thanks. I will be wiring up a DL-1 in a similar fashion.

So you leave the Racepak on when you crank the starter?

OBD-II doesn't offer much add'l - you will easily get rpm, oil press and water/oil temp, volts and other stuff that is not useful for driving (O2 sensors, etc.).
It would be really nice to get readings from each wheel speed sensor via OBD II. Most dataloggers need a pulsed output, not the A/C output that the sensors give (why couldn't they have used hall effect??!!). I don't think you'll gain anything with the OBD II setup (the oil pressure sensor is easy to add, given what you have already done).

A question about the steering angle sensor - does your formula essential sum the voltage inputs? Or rely on one sensor up to a certain angle, then rely on the other? Is there a way to reduce this to a single output wire?

Kudos to AiM for getting that part right. I do with I had a CAN car.

MySR71

Sorry guys. I accidentally deleted my post. This is basically what it said:

I use a Racepak G2X on my 2002 C5 Z06 along with a couple of their Universal Sensor Modules (USM's). Using USM's, I currently log:

1) Accelerator Pedal Position
2) Brakes on-off
3) Brake pressure at the ABS unit (no real way to calibrate it so I just record voltage)
4) Steering wheel position channel A
5) Steering wheel position channel B
6) Oil temperature (measured using the wire going to the dash)

Ok, so on my 2002 C5 Z06, here's what I've discovered. Many of the sensors are powered. That means the sensors have 5 volts going to them, a ground, and then a separate line as the sensor's output. This output line often varies 0-5 volts and can be directly connected a USM's signal input. I have been told that you likely can't have non-powered sensors operate properly for both the car and be used for the data system.

Accelerator Pedal Position: if you look up in the manual (page 6-623 in my 2002 service manual), you'll see the wiring layout for the accelerator pedal position sensor's connector. I spliced into the APP Sensor 1 Signal wire. Connect this to the USM's input signal. Calibration in the Datalink software is easy. Leave the accelerator in it's non-depressed condition and that's 0% throttle. Floor the throttle and set the corresponding voltage to 100%.

For brakes on/off, tap into the line under the dash for the switch on the brake pedal. I THINK, but don't remember exactly if it is the Stop Lamp Switch C2 on page 8-237. You probably don't want this on-off measurement though. Why? Because you can get relative brake pressure instead (see next paragraph)!

Now, if you want to know how hard the driver is pressing on the brake pedal, that can be done too (and is really better than a simple brakes on/off). It turns out that there is a brake fluid pressure sensor on the ABS unit in front of the engine. See page 5-117. I spliced into the sensor signal there. Now I don't know how to convert the output voltage to PSI, but I can show how hard I was pressing on the brake pedal and how the pressure varied in a braking zone. That is, you can just graph the raw voltage trace.

Steering wheel position is a little harder. Check out Steering Wheel Position Sensor pin out on page 2-166. This connector is also under the dash. I record the output from both signal A and signal B. I then have a math formula, "IF('Steering Angl 1'>2.5,36*'Steering Angl 2',-36*'Steering Angl 2')" that converts the two signals into a steering wheel angle. The above formula works on my car for steering angles of plus or minus 180 degrees.

So the above is how I get accelerator pedal position, brake pressure (in volts), and steering wheel position using four USM channels. I also log oil temperature using one of the wires going to the dash (page 8-501, wire A10). To calibrate this line, I correlated the voltage going to the USM with the oil temp shown on the DIC. Engine RPM is in that same bundle if you don't already have that connected.

I haven't done it yet, but the oil pressure sensor also looks to be a powered sensor that we can splice into. I REALLY want to get that one but the wiring is a little more difficult to get to and I haven't poked around enough with it yet.

So all the above works on my car (your car may be different) on using the car's already existing sensors to operate the car and be logged by the data system. There is one downside that I have found to doing this. I have to have my G2X turned on whenever I start the car. Otherwise I get codes set for the active handling system. I don't understand all the details of this but it has something to do with splicing into the steering wheel position sensor and/or the throttle position sensor and how the Universal Sensor Module works. If the USM doesn't have power, it screws up the output from the sensors and the car sets codes. So I turn on my G2X before I start the car and leave it on whenever the car is running. It is not a big deal in my mind but something you should be aware of. When done running the car, I turn off the car and then shut off the data system.

Also, the oil temperature read on the DIC is wrong if the data system isn't powered up.

I'm not really what parameters are available through the OBD II port but Racepak says they will have their OBD II module available by the end of the month. You can check out their web site and their forum for some details.

MySR71

One more interesting thing to note: The brake pressure sensor seems to be downstream of the ABS pump (I may have my terminology wrong here). As a result, you can see if active handling is kicking in (for those that use it) by checking to see if the there is brake pressure but the brake pedal is not depressed.

There are some neat books out there about interpreting data. While it is fun to acquire data, interpreting is also required.

MySR71

Yes, the data system is on when the starter is cranking. So I typically turn on the data system, then start the car. When shutting the car down, I turn off the ignition and then turn off the data system. So the data system is first on and last off.

I'm not really sure what parameters will be available through the OBD II port but logging temperatures sound like a good job for the slow OBD II port. They shouldn't be changing quickly so low sample rates should be fine. I see this more of use to monitor car health.

The wheel speed sensors aren't powered on the C5's, at least not on mine. I've read where people have spliced into them and messed up the car's ability to work properly. I agree that logging the rear wheel speeds would be interesting to see how the differential is working.

Each channel of the steering angle sensor's output is a sinusoidal curve. The difference between the two channels is the curves are out of phase with each other. Based on the phasing, you could splice into channel 2 and you'll get steering angles from 0 to +/- 180 degrees but you won't know if they are + or -. The formula that I use then checks channel 1 to determine if it is + or -. Do you need that? Not really as you should be able to tell whether it is a right hand or left hand turn based on where you are on track. I believe you can just record channel 1 then then get +/- 90 degrees and you will know the + and the -. Hopefully all this makes sense. If not, I can try and explain it differently.