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Stock cluster VSS signal parameters

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  • citizen_insane
    replied
    Originally posted by Jaxx_ View Post
    Only the cam and PT4 inputs are "high speed." If you have a high speed signal like an abs tone ring, I believe you can use a VR conditioner into a regular input to prevent the drop out issue. I don't know what frequency is the hardware's limit... I'm sure you could figure it out with tire size knowing 200kph is the limit on 9 teeth.

    I also recall other inputs able to take 12v or nitrous taking ground. It's essentially just a trigger circuit pre built for 12v–similar to how you can modify JS10 to take 12v or ground. Maybe I'm making this up. Refer to the manual of course.
    It probably just depends on whether or not the input has a pull-up resistor installed in the normal configuration or not.

    In order to get more clarification, I've also posted this question on msextra and I will report back what I learn.

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  • Jaxx_
    replied
    Only the cam and PT4 inputs are "high speed." If you have a high speed signal like an abs tone ring, I believe you can use a VR conditioner into a regular input to prevent the drop out issue. I don't know what frequency is the hardware's limit... I'm sure you could figure it out with tire size knowing 200kph is the limit on 9 teeth.

    I also recall other inputs able to take 12v or nitrous taking ground. It's essentially just a trigger circuit pre built for 12v–similar to how you can modify JS10 to take 12v or ground. Maybe I'm making this up. Refer to the manual of course.

    Leave a comment:


  • nando
    replied
    It does, but you have to read all the links below, notes, etc.

    But I would be willing to fix problems you've had with it to make it more clear. I just haven't looked at or touched it in almost 10 years because I haven't had to. Honestly I don't even remember how I built half of that stuff, lol.

    Actually I'm kind of amazed anyone even used that chart, I mostly just made it for my own reference while I was building everything..

    Leave a comment:


  • pazi88
    replied
    Originally posted by nando View Post
    That's mine. I also have additional circuits to handle the other stuff, for example the circuit that activates the main relay. It definitely works - my car has run the same MS3 setup since 2010. I've never had an issue with the PWM idle.
    Probably yes in that case. But the sheet doesn't clearly say that extra circuity is needed or even what kind, so that leads people wiring up everything directly to ms3 pins and then wonder why it doesn't work. I would advice to add more info there. I don't want to be rude but it's annoying have to deal same problems caused by that diagram many times.

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  • nando
    replied
    That's mine. I also have additional circuits to handle the other stuff in the proto area, for example the circuit that activates the main relay is the reason for using that pin (you could use any free pin, I just chose that one). If you read the links at the bottom it makes sense:
    http://www.megasquirt.325ix.com/MS_t...t_Circuit.html. My stock tach works just fine. *shrug*

    It definitely works - my car has run the same MS3 setup since 2010, I was probably the first E30 or M20 to run it. I've never had an issue with the PWM idle, and I daily drove it until recently. I got bored of it though, I haven't touched the firmware or tune since 2012.
    Last edited by nando; 01-10-2019, 03:05 PM.

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  • pazi88
    replied
    Originally posted by nando View Post
    I used the N2O input on the MS3X:
    http://megasquirt.325ix.com/MS_to_Mo...c%203.3.1.html

    But there's a difference here - Pazi might be using MS2, which has a slower CPU - the N2O input on my MS3X was plenty fast enough as far as I can tell, as the MS3 uses a newer, faster CPU. Also according to my own notes (which I don't remember typing, lol), you can also use any of the extra ADC inputs for VSS.
    No. Ms3x too and n2o input too. I did read about that same vss input sampling problem on many places and solution was to use pt4 input. I noticed the same problem on the other e30 also with ms3x. The ms3x is of course faster than ms2, but only few inputs have fast sampling rate. As far as I know only pt4 is something that can be used for this purpose. Could be others, but i didn't find documentation about sampling rate of each ms3x input.

    OT: that connection diagram available on that link. Who made that. I have worked many hours trying to solve strange megasquirt problems, and it has all come to people using that diagram. Like why the +12v from ignition switch goes to iac2? Js11 can't drive tach out without extra circuitry, so why it's connected directly to tach line? Icv pin to fidle. Way to failure because fidle ouput can't handle the current required by idle valve for long periods of time. It would need 2wire pwm mod. Also that easily leads to power loops that cause megasquirt to not turn off..
    Last edited by pazi88; 01-10-2019, 02:55 PM.

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  • citizen_insane
    replied
    Originally posted by nando View Post
    I used the N2O input on the MS3X:
    http://megasquirt.325ix.com/MS_to_Mo...c%203.3.1.html

    But there's a difference here - Pazi might be using MS2, which has a slower CPU - the N2O input on my MS3X was plenty fast enough as far as I can tell, as the MS3 uses a newer, faster CPU. Also according to my own notes (which I don't remember typing, lol), you can also use any of the extra ADC inputs for VSS.
    Thanks for the confirmation. I know how the "trusting your own notes" thing goes. I'm trying to stay organized with the build but the documentation definitely leaves something to be desired.

    Leave a comment:


  • nando
    replied
    I used the N2O input on the MS3X:
    http://megasquirt.325ix.com/MS_to_Mo...c%203.3.1.html

    But there's a difference here - Pazi might be using MS2, which has a slower CPU - the N2O input on my MS3X was plenty fast enough as far as I can tell, as the MS3 uses a newer, faster CPU. Also according to my own notes (which I don't remember typing, lol), you can also use any of the extra ADC inputs for VSS.
    Last edited by nando; 01-10-2019, 12:24 PM.

    Leave a comment:


  • citizen_insane
    replied
    Originally posted by nando View Post
    if you have MS3x you should have plenty of inputs for VSS. I'm sure I have done over 120mph while logging (on a track) and I never saw a dropout, but I don't recall which input I used.
    The issue is that as far as I can tell, Nitrous In is the only one that takes 12V signals. I'd prefer not to have to add extra circuitry to reduce the voltage, even though it's easy enough to do.

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  • nando
    replied
    if you have MS3x you should have plenty of inputs for VSS. I'm sure I have done over 120mph while logging (on a track) and I never saw a dropout, but I don't recall which input I used.

    Leave a comment:


  • citizen_insane
    replied
    Pazi, thanks for the info. That sounds like an issue, the car will definitely be driven on track above 200km/h. I'll see what the rest of the MS3X community think and report back, but I'm thinking the best option would be to use the PT4 input with a voltage divider to reduce the signal to 5V max.

    Leave a comment:


  • nando
    replied
    That's good info. I can't say I ever went 200km/h with my MS2 though. I think MS3 has a faster CPU and more I/O, so this probably wouldn't be an issue.

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  • pazi88
    replied
    Originally posted by citizen_insane View Post
    Awesome, thanks for the confirmation!


    100% I plan to use the cluster to process the signal since I'm still running it (my secondary tablet dash will be mounted to the dashboard center console).

    Based on this statement, I think the "Nitrous In" input is the correct one to use since it'll be providing voltage to the pins on the MS3X.

    Jaxx, you're right on the money with the VSS/RPM gear calculations. My plan is to run a blend table for boost by gear to maximize traction.
    That's right. You can use nitrous-in directly for vvs input from cluster. It's 0-12v square wave. And the cluster between the reed switch sensor and megasquirt is mandatory for debounce purposes.

    But all this has catch. The speed how fast the megasquirt inputs can accept signal is quite limited. Even with that 9 pukses per rotation, the nitrous in input will saturate at about 200km/h speeds and the speed will go to zero. Making the boost lower. Like happened me on this 1/4 mile pull:


    Only fast enough input is pt4, but it's 0-5v logic input. Which would need converter between. I have now second vss from front wheel abs sensor using max9926 vr-conditioner which signal goes to pt4 input. That works great on higher speeds also. And I csn use the tracktion control on ms3x too. But still because of the slow nitrous-in I have to switch of TC before 200km/h.

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  • nando
    replied
    It also adjusts the output rate (k factor). If I find it, I'll post it.

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  • bmwman91
    replied
    Originally posted by nando View Post
    It goes through a processor that's specifically designed for VSS signals. I have the datasheet somewhere, if I could remember what it was called.. lol.

    I assume it is to de-bounce the signal from the switch and isolate any possible EMI / ESD issues? If you find a PN or datasheet I'd be interested to see it.

    Leave a comment:

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