Adaptronic MVSS noisy speed..... aka its bouncing all over
#1
MVSS noisy speed..... aka its bouncing all over
So i need some help trying to get my launch control to work.
My MVSS1 is not working properly and is all over the place. the wiring diagram does show we could use a signal from the speedo
I have a FC3S and i am using the oem speed sensor that comes from the speedo and goes into the cruise control its green with red stripe.
you can see link here FC3S Pro v2.0:  Tips 'N Tricks - Cruise Control Speed Sensor Wire
see log attached, any help here would be appreciated, maybe i am missing something.
Hybrid
My MVSS1 is not working properly and is all over the place. the wiring diagram does show we could use a signal from the speedo
I have a FC3S and i am using the oem speed sensor that comes from the speedo and goes into the cruise control its green with red stripe.
you can see link here FC3S Pro v2.0:  Tips 'N Tricks - Cruise Control Speed Sensor Wire
see log attached, any help here would be appreciated, maybe i am missing something.
Hybrid
#6
Lots of searching but no leads yet but I did get a lead from the adaptronic forum
MVSS1 noisy ..... aka speed is bouncing all over the place
aka solution buy a sensor which is pretty shitty there is not a straight forward explanition for this.
MVSS1 noisy ..... aka speed is bouncing all over the place
aka solution buy a sensor which is pretty shitty there is not a straight forward explanition for this.
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#10
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Hi guys,
I haven't work on an FC before, so I haven't encountered this speed signal fluctuation yet. But looking at the factory diagram, I see two possible things that may cause the noise. One is that the actual sensor is a reed switch. For those who are not familiar, you can check this link - https://en.wikipedia.org/wiki/Reed_switch
The problem with a reed switch is that the two contacts actually bounce a bit when they close - like when you drop something on the floor it doensn't usually go splat. That will cause some high frequency noise, and although we have some filtering available in the ECU, it still has to work with systems with normally high frequency inputs like ABS sensors so we couldn’t filter out enough for the reed switch contact bounce. Another thing that might cause the noise is that the reed switch uses the chassis ground (i.e. not a sensor ground) which we want to avoid because those grounds are usually noisy. So after talking to Andy, he suggests to put a 100nF capacitor between the VSS input and SGND (sensor ground) and see if that helps.
The FD should be different though i.e. doesn't use reed. For the FD guys who has this problem are you getting the speed signal from the factory location?
Thanks.
Mark
tech@adaptronic.com.au
I haven't work on an FC before, so I haven't encountered this speed signal fluctuation yet. But looking at the factory diagram, I see two possible things that may cause the noise. One is that the actual sensor is a reed switch. For those who are not familiar, you can check this link - https://en.wikipedia.org/wiki/Reed_switch
The problem with a reed switch is that the two contacts actually bounce a bit when they close - like when you drop something on the floor it doensn't usually go splat. That will cause some high frequency noise, and although we have some filtering available in the ECU, it still has to work with systems with normally high frequency inputs like ABS sensors so we couldn’t filter out enough for the reed switch contact bounce. Another thing that might cause the noise is that the reed switch uses the chassis ground (i.e. not a sensor ground) which we want to avoid because those grounds are usually noisy. So after talking to Andy, he suggests to put a 100nF capacitor between the VSS input and SGND (sensor ground) and see if that helps.
The FD should be different though i.e. doesn't use reed. For the FD guys who has this problem are you getting the speed signal from the factory location?
Thanks.
Mark
tech@adaptronic.com.au
#17
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Did you attempt the capacitor?
I'm nearly to the point on my s5 t2 where I actually will be worried about this and will attempt the suggested capacitor but it may be a while til I get around to it.
With the reed switch wiring as is stock my speed numbers are virtually random.
I'm nearly to the point on my s5 t2 where I actually will be worried about this and will attempt the suggested capacitor but it may be a while til I get around to it.
With the reed switch wiring as is stock my speed numbers are virtually random.
#20
Exhaust Manifold Leak
i measured also the signal from the reed switch.
1st is with no cap
2nd with 10n and 3rd with 100n
#22
Exhaust Manifold Leak
Okay, but I think at this time finding a mint FC cluster that hasn't even has a little noise in the contacter will be kind of a miracle for most of us.
If you look on the screenshots of the scope I posted, even without the cap the noise is really minimal and I feel the processing of the signal should not be rocket science to let it work.
I do not know how the signal processing is at this time, but if there would just be a comparator with a voltage threshold of 1.5v for example (depending on the pull up voltage). then it should work 100% fine even without adding a cap.
#23
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Okay, but I think at this time finding a mint FC cluster that hasn't even has a little noise in the contacter will be kind of a miracle for most of us.
If you look on the screenshots of the scope I posted, even without the cap the noise is really minimal and I feel the processing of the signal should not be rocket science to let it work.
I do not know how the signal processing is at this time, but if there would just be a comparator with a voltage threshold of 1.5v for example (depending on the pull up voltage). then it should work 100% fine even without adding a cap.
If you look on the screenshots of the scope I posted, even without the cap the noise is really minimal and I feel the processing of the signal should not be rocket science to let it work.
I do not know how the signal processing is at this time, but if there would just be a comparator with a voltage threshold of 1.5v for example (depending on the pull up voltage). then it should work 100% fine even without adding a cap.
Sure but I was referring to FDs. Sorry if it wasn't clear.
#25
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Interesting to hear about the cluster part, as I didn't have any problems with my speed reading fine on the adaptronic. But I recently changed my motor mounts and for some reason the odometer and trip part went out and now the speed on the adaptronic is erratic as hell.
Quick search this is what we are talking about. Post #51
https://www.rx7club.com/3rd-gen-arch...2/page4/?pp=15
It goes from the transmission to the same ECU opening in the firewall, and connects under the passenger side dash.
Off the top of my head I think it is a blue connector in the cabin.
Last edited by silentblu; 06-03-17 at 07:19 PM. Reason: Added info.
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