Motec M800 Loss of connection to laptop via CAN

[garychios]

Motec M800 Loss of connection to laptop via CAN.

Car: Mitsu 4g63
16 Volt System (No Alternator)
4 Cylinders
COP (Sequential)
8 Injectors (Staged)
Methanol
Lamda Control on ECU
Boost Control via ECU.


I have a M800, A AIM Pista and a M&W Pro Drag 4 in the car. I started to get loss of connections to the ECU on the can bus. This happens at anytime, idle, reving etc.

I was told to move the m&W away from the ECU. I did. I put in the engine bay (but now need to clean up the slack). The location in the engine bay is in front of the driver.
I also ran longer trigger wires for the 4 channels from the ECU to the M&W keeping the waires away from any voltages.
I ran power and ground straight from the Battery to the M&W to try and clean up the signals.

ECU is grounded with the rest of the wiring in the car for fans, relays etc.

I basically loose connection to the laptop from the ECU. Only fix is to unplug the USB cable on the laptop and plug it back in and I reestablish connection. The display never looses the connection and the car runs flawlesly. We are only able to tune in approx 5 minute intervals which is the amount of time before I get disconnected etc..

I installed two 1/4 watts 100 ohm resistors on the CAN bus. WIth the UTC, the Resistance is 30 Ohms.
I also removed the Dash board and still get the disconnects.
I purchase a new UTC and still have problems. (But forgot to check the firmware on it). The original was flashed to 1.13.

The only thing I can say is that the disconnects are a lot less frequent since I moved the M&W and ran power and ground to the battery. The M&W though is close to the display now on the opposite side of the firewall.



Please, any suggestions?

[Holmz]

It is most likely either an issue with either noise on the signal or a ground loop.
If you tune an AM radio between stations and crank up the volume you can get an idea as to whether there is a great deal of highfrequency noise that it might be generating...

Really you need to get a scope on the power and on the CAN bus.
We know it is not noise from your alternator.

You will want the CAN bus wires run as a twisted pair.
But all other wires that run anywhere near it should also be twisted unless they are carrying only DC.
Relays, pumps, etc, all are DC, untill you look at switching with a scope... So all the wire should be twisted except for the starter motor and regular (non-HID) lights.
So the power and ground to the units - those should be twisted as well.
Do NOT run power and then just run a ground to the nearest part of the chassis - keep them together and twisted.
Or you can get (high frequency AC) power into the box from the +/- which can be as bad as through the CAN bus itself.
If you have one of those big capacitors that are used for Audio amp or even a small capacitor, you might see of attaching that near the unit's power inputs and ground helps.
Usually you would do this after putting a scope on and filter the power as a last resort.

[garychios]

Thanks for the reply, and I apologize on my grammar. It was late last night.

A couple of more things since I forgot to mention them.

It is a drag racing car. So the car has only what is needed to run.
No Head lights, No alternator or much of any wiring.

I do ground right away to the chasis as you mentioned. I have always done this.

The CAN wires are near nothing. The wires to the CAN are from Motec ECU straight to the UTC with the Motec provided short wire with the round plug for the UTC. It's approx 2 inches. I then piggy back off of that for the AIM CAN signals which are also twisted.

I will twist the power and ground wires at this point and see what happens.

Thanks for the info.

[Martin]

Hi,


1. What ECU firmware are you running?
2. How long is your USB cable to the UTC?
3. Have you tried another laptop?

[Holmz]

OK I originally read that t was a lap top issue in the title, but then sounded like it wasn't.
But now I understand.

I would agree with martin, you should try another computer.
I had issues with one only getting some data, and switched computers are everything was ok after that,
USB-RS232 converters are the worst.
I have 4 and only 1 works without conflicting with snomething else.

[garychios]

Hi again.

3.51 Firmware/Software

UTC is 1.13

USB Cable is 6 foot

I tried two diff laptops of the same make and model. Dell D420 and D430 which has a slight revision.

I dont use converters. It is straight USB.

[DarrenR]

Communications are fairly susceptible to noise, and seeing as you had an improvement when you moved some ignition components it is fairly clear this is the problem.

It sounds more like a USB problem than CAN. I would try a shorter or better shielded USB cable. Or better still run an extension on the CAN bus and move the UTC and laptop right away from the car to see if it helps. You only need the two CAN wires to the UTC.

What other CAN devices are on the bus? You might like to set the baud rate to 500kbits (Tools|Options) for a test as a slower CAN speed can be more reliable.

[Martin]

Darren,

Dont you need the 0v to go to the UTC aswell?





I think a shorter USB cable might help.

[garychios]

Hey guys. Some closure to this thread.


Details.

I had random disconnects to the ecu from the laptop. I did not loose connection to the UTC because windows did
not make the USB disconnect sound as it normally would. I just basically got an error in the software saying the ECU is not connected. This happend randomly without any one particular situation I.E reving, idle etc.

I had the ECU and the M&W together in the passenger seat. I moved the M&W to the engine bay and ran power and ground to the M&W from the battery in the back of the car.


Still had random disconnects, but a lot less of it.

I then bought another UTC, and at the same time, picked up a high quality 1.5 foot shielded USB cable. With that said, I had a 4 hour session and no disconnects.

I believe the USB cable I bought fixed the problem. since I tried both UTC's and both are not disconnecting now.

Thanks everyone for the suggestions.








I moved the M&W Prod Drag 4 into the engine bay.

[timlothian]

Thanks for the help on this one. Sounds like the roots of my problem, posted only a few threads down the list.

Having thought about it, I have a 3 metre usb cable, unsure of the shielding status, and both the usb and the UTC hang down directly over the CDI (dyno setup wiring board). Now that I think of it, I am just asking for noise!

I am yet to see if moving them makes a difference, but I am hopeful from what I read above. Will post my results too.

Thanks agin!