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Trail Tech Vapor Tach Problems

  • Thread starter Thread starter Guest
  • Start date Start date
mmattockx said:
It turned out I didn't have mine as sorted as I thought in post #4. I still had noise issues that I struggled to get sorted. The eventual answer was to solder a resistor into the tach line and connect to the negative side of the coil. The resistor was a 680K Ohm unit, but I don't think that was critical. It just cut the noise spikes and let the Vapor read the signal properly. When I put the resistor in line I was unable to get a signal at all from the positive side of the coil and I had pretty much given up on making it work. My supplier had mentioned that the negative side of the coil is noisier than the positive side, so I thought I would try it as a last shot and then give up if that didn't do it. Worked like a charm, with a solid, steady signal. It has been working perfectly for close to 2000km since. At this point I will say I have it truly sorted and will likely ditch my OEM instrument cluster over winter and use the Vapor exclusively from here on.

If I ever use a Vapor on another bike I will head straight to the resistor lead and the negative side of the coil instead of wasting a bunch of time with half measures.


Mark
Click to expand...

The input impedance of the Vapor-trail is probably pretty high as it is an input. Say 10-100K ohms. So when you put a resistor in series with that it has the effect of scaling the coil voltage by what is know as a voltage divider formed by the input impedance and the series resistor. If the input impedance is 100K ohms, then the voltages will be scaled by 100/(100+680)=100/780 or 0.12 . That is close to a reduction of 10:1 in the input voltage spikes.

I don't know why this is not included in to teh Vaportrail itself, unless they are trying to use a single input as either a high tension coil wire input of a primary wire input. The circuit I provided will limit the current and voltage to the range of -0.5<V<5.0 and should make the Vapor-trail happy as well.

Just a guess, since the vapor-trail has a sensitivity that requires this input conditioning, I would have a concern about damaging it with inductive spikes from the ignition. The circuit I provided would prevent overloading of the input signal which I suspect is the issue in the first place.
 
posplayr said:
I don't know why this is not included in to teh Vaportrail itself, unless they are trying to use a single input as either a high tension coil wire input of a primary wire input.
Click to expand...

I don't know what they are trying to do either, but they do offer tach leads with a resistor from the factory and I think that should be the standard lead, not an optional extra. I can say the thing works great now that I have the tach feed sorted but it was a first class PITA to get it working correctly. The instructions do say you can wrap the lead around a plug wire or use either side of the coil inputs.


Mark
 
Last edited:
mmattockx said:
I don't know what they are trying to do either, but they do offer tach leads with a resistor from the factory and I think that should be the standard lead, not an optional extra. I can say the thing works great now that I have the tach feed sorted but it was a first class PITA to get it working correctly. The instructions do say you can wrap the lead around a plug wire or use either side of the coil inputs.


Mark
Click to expand...

Well base on this additional data, I would say that the TACH input is expecting a low level signal (<1 volt) as you would get with wrapping a wire around a high tension coil wire. Since it is a low level signal noise would be an issue unless you put a whole lot of wrapps around the high tension wire.

Using the primary side without a resistor (0-12V signal with 50 V inductive spikes) is completely overwhelming the TACH input that expects the low level from the secondary.

I would think that the limiting circuit (I posted) would actually be better as it should clip the signal reducing most of the noise but it maybe the design works well enough with just a series resistor.
 
Well it seems connecting the tach lead to two diodes that connect to both coil negative terminals seemed to do the trick, although I haven't taken it out for a spin yet. The diodes prevent current from crossing over between negative terminals. I changed the PPR (pulses per revolution) setting to 2, which at 10,000 RPM will signal once every 3ms, so we'll see if there are any issues there.

For me I don't think the issue is the magnitude of the voltage spike. It seems that there is voltage feedback from the other coil when hooking it up to just one coil, and I really don't know how to eliminate that. Either it's inductance in the wire from either the coil or the plug wires, or there's some feedback from one primary through the other primary? I don't know.

I'll post back when I take it for a spin and get the RPMs up. My bike is loud, and it's 10pm...
 
Took it out for a spin today. RPMs are rock solid and steady up to at least 8k. Finally!

I still might play around with creating a tachometer using an Arduino this winter, maybe with the Adafruit Neopixel ring.
 
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