DadJorts
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« on: April 19, 2020, 07:59:30 AM »
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Looking for some idea's from anyone who's got a couple more brain cells than i do. Last year i swapped my b3 passat with a 2.8 24v (dont ask me why).
My issue is self inflicted, prior to the swap i didn't have the foresight to harvest a sample of the tach signal which originally was supplied by the old ECM. To add to this, me7.1 uses CAN for VS for tach display which is obviously not supported by the stock b3 cluster. ABS module was included in the swap, and is supplied with k-line, can, wheel speed etc.
My original idea was to attempt to convert the can "signal" into an analog output the cluster could use (if thats even possible), or attempt to generate a tach signal off coil signals with an arduino etc, but im seeking some advice on possible easier ways to do this.
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dal
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« Reply #1 on: April 19, 2020, 12:40:05 PM »
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I dont know in your car, but on my A3 (8L) and GTI MK4, the signal generated in the tranny VSS is a square wave. The speed the cluster shows is proportional to the frequency of this square wave.
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DadJorts
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« Reply #2 on: April 19, 2020, 01:12:25 PM »
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I appreciate the input, but i'm talking about tachomter, not vehicle speed.
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dal
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« Reply #3 on: April 19, 2020, 02:21:15 PM »
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Sorry, I'm facing an similar problem on my car but related to VS. So I'm with this stuck in my head.
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BlackT
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« Reply #4 on: April 19, 2020, 02:26:48 PM »
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Passat B3 schould have VSS 12V output from tacho( it use it for GRA)
And you can reprogram ECU to use 12V VSS.
If understand correctly your problem?
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DadJorts
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« Reply #5 on: April 20, 2020, 06:55:29 PM »
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Sorry, I'm facing an similar problem on my car but related to VS. So I'm with this stuck in my head.
No worries! |
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DadJorts
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« Reply #6 on: April 20, 2020, 07:00:57 PM »
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Passat B3 schould have VSS 12V output from tacho( it use it for GRA)
And you can reprogram ECU to use 12V VSS.
If understand correctly your problem?
Yes, VSS is provided via 12v VSS on trans. What im after is the TACHOMETER signal that is generated via the b3 ECM (which i am not using) and sent to cluster. The swapped drivetrain doesn't utilize a physical signal for tachometer control, its done via CAN. What im asking is if anyones aware of software based option to remedy this (hypothetical example, modifying the "consumption" signal provided via the ECM for MFA. |
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BlackT
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« Reply #7 on: April 21, 2020, 12:56:15 AM »
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No I don't think is going like that. I never own B3 but I have a lot of audis and I worked on some MK2, MK3. They work all on same principle G22 is VSS sensor om transmition, it is reed relay that closed ciruit to ground when gear pinion is rotating on transmition. That signal goes to cluster, then cluster outputs 12V VSS for GRA and ECM. Look at this pinout https://i36.photobucket.com/albums/e15/Gregathon/MKIIIdashpanelpinout.jpgPin 22 is G22 sensor on trans, pin 7 is VSS output 12V That is how every VW/AUDI works from 1985 until 2000. And I am sure passat B3 have same principle |
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adam-
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« Reply #8 on: April 21, 2020, 01:27:33 AM »
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He's talking about the tach. RPM... |
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BlackT
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« Reply #9 on: April 21, 2020, 02:01:29 AM »
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Aa okay my bad didn't read well. Easy whey is to buy some CAN to analog interface, I see some of these on ebay or similar pages. Or you can build your own with arduino https://www.electronicshub.org/arduino-mcp2515-can-bus-tutorial/If you don't want to mess with CAN you can make as I did, arduino to read CKP sensor, than make output to tachometar. I can upload program and shematic |
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prj
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« Reply #10 on: April 21, 2020, 07:47:11 AM »
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On ME7 it is configurable whether the signal is CAN or normal one, and there is a dedicated pin on most ME7 that has an analog pin with the PWM signal.
IIRC it's even adjustable in the cal.
So you need to modify the cal and also find which pin has the signal. Maybe a good idea would be to find a car with an analog tach signal with a similar ECU. It is likely it will be in the same place.
For example, pre-facelift 2.7TT has analog signal output. You can try to look at the wiring diagram for that.
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DadJorts
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« Reply #11 on: April 21, 2020, 12:51:35 PM »
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On ME7 it is configurable whether the signal is CAN or normal one, and there is a dedicated pin on most ME7 that has an analog pin with the PWM signal.
IIRC it's even adjustable in the cal.
So you need to modify the cal and also find which pin has the signal. Maybe a good idea would be to find a car with an analog tach signal with a similar ECU. It is likely it will be in the same place.
For example, pre-facelift 2.7TT has analog signal output. You can try to look at the wiring diagram for that.
That's stellar info sir, thank you! Definitely gonna do some digging on that |
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« Last Edit: April 21, 2020, 12:54:27 PM by DadJorts »
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DadJorts
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« Reply #12 on: April 21, 2020, 12:53:54 PM »
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Aa okay my bad didn't read well. Easy whey is to buy some CAN to analog interface, I see some of these on ebay or similar pages. Or you can build your own with arduino https://www.electronicshub.org/arduino-mcp2515-can-bus-tutorial/If you don't want to mess with CAN you can make as I did, arduino to read CKP sensor, than make output to tachometar. I can upload program and shematic Those were two other options i was looking into as well, and yeah if you wouldn't mind uploading that or sending it my way that would be much appreciated, i can definitely learn from your design! |
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