LC-1 gauge doesn't match Megatune gauge

[bmcewen]

Something with the two analog outputs is not meshing well I have one going to the gauge that comes with the lc-1 and the other going to the relay board megat tune will read around 14.7 +/- and the Lc-1 gauge reads around 14.2 +/- any suggestions on how to fix this?

[Matt Cramer]

Where are the MS and the LC-1 grounded? This sounds like a ground offset issue.

[EWflyer]

Where are the MS and the LC-1 grounded? This sounds like a ground offset issue.

Okay Matt, now I'm interested...

If the MS and the LC-1 are grounded to different places and because of this are "seeing" slightly different A/F ratios, which of the two is likely to be more accurate?

I ask because I've noticed that my Kawasaki EX-250 project bike has the same, very small, discrepancy between the Innovative Motorsports Stand-Alone gauge on my instrument panel and the Microsquirt. The Microsquirt reading is always slightly higher than the Stand-Alone gauge.

I honestly can't remember how/where I wired the ground lead for the Innovative O2 sensor controller and to complicate matters further I think the gauge has a ground wire of it's own, so there's really three grounds involved (gauge, controller, and microsquirt). I'd be willing to bet I wired the O2 controller ground to the sensor-ground line of the Microsquirt (along with the TPS, MAP, etc.) but I can't recall what I did with the Stand-Alone gauge ground line. It's funny to think back and realize that I gave the location of the gauge ground line no consideration at all, probably just hooked it up to whatever ground line was handy there at the instrument panel of the bike. Maybe I'll chase the wires to figure it out.

Although, if I hadn't installed the Stand-Alone gauge I would simply assume that the Microsquirt was getting a good signal from the (hopefully correctly installed and calibrated) Innovative O2 controller. If I didn't have the two readouts to compare I'd never be asking this question.

[Matt Cramer]

Where are the MS and the LC-1 grounded? This sounds like a ground offset issue.

Okay Matt, now I'm interested...

If the MS and the LC-1 are grounded to different places and because of this are "seeing" slightly different A/F ratios, which of the two is likely to be more accurate?

The LC-1's digital output, as seen by an XD-16 or laptop running LogWorks. An analog gauge is just as vulnerable to ground offsets as the MS.

[bmcewen]

Well it would be nice to know which is more accurate the ms or the gauge, so after i compare the readings to logworks I'll change the grounds around I'm pretty sure that the controller and the gauge are grounded to the same point under the dash (possibly the same ground point as the radio which im fairly certain was a bad idea) and the ms shares a common ground with the engine block on the fire wall

[trakkies]

I reckon the best place to ground the MS is the engine block. And all sensor grounds must be brought back to the same point on the DB 37 connector. This can be difficult due to space inside in, so I ran a short wire to just outside the shell and made all the sensor connections to that.

[Matt Cramer]

Well it would be nice to know which is more accurate the ms or the gauge, so after i compare the readings to logworks I'll change the grounds around I'm pretty sure that the controller and the gauge are grounded to the same point under the dash (possibly the same ground point as the radio which im fairly certain was a bad idea) and the ms shares a common ground with the engine block on the fire wall

In that case, the gauge *should* have less of a ground offset problem than the MS, but I don't recommend anything about your grounding layout. I would recommend grounding MS, gauge, and LC-1 to the engine block itself, not chassis sheet metal.

[bmcewen]

Well that sucks now i have to move all my ground wires to the other side of the grounding strap ...thats like 3 inches

[trakkies]

Well that sucks now i have to move all my ground wires to the other side of the grounding strap ...thats like 3 inches

But what about the sensor grounds? I dunno the LC-1 - my Tech Edge has separate power and output grounds. Ideally, you keep those things which take power separate from the low level signal grounds. And the sensor heater takes power.

[bmcewen]

"Connect the gauge’s BLACK ground wire at the LC-1’s White ground point. This ground point should ideally be an engine block ground."

This white wire would be the sytem ground the heater ground is a blue wire although Innovative reccomends placing all grounds to one location...

1. The BEST grounding scheme is all grounds (i.e., ECU, Gauges, LC1 heater, LC1
system, etc.) SOLDERED into a single lug and bolted to the engine block.

2. The next best is all grounds attached to the same source, as close as possible, but on
separate lugs. This is because even the corrosion between lugs can create ground
offset and noise. Incidentally, this is why many ECUs have separate ground wires for
injectors vs. ECU system ground- separating high voltages and low voltages reduces
noise.

3. Grounding to the engine block is usually better than grounding to the frame.

4. Grounding a gauge to the radio is usually bad- ground offset can vary with volume.

5. Grounding to an ECU housing is generally not optimal- housings are strapped to the
frame for shielding, but not necessarily grounded.

6. One of the WORST things to do is to ground most of your electronics to one place (i.e.
the engine block), but ground one device somewhere else (i.e., the frame). Not only can
this result in ground offsets, it can also create a “path of least resistance” for high
currents THROUGH a low-current device. This can result in melted wires and vaporized
diodes, when, for example, starter currents flow through gauges.

[bmcewen]

Well I rerouted all grounds to the engine block( well the back if the head) but that changed nothing the two guages are still different, both outputs are programed the same in lm programmer

[bmcewen]

My lc-1guage reads the same as logworks but Ms is still reading leaner by about 1, eg. 13.8 vs 14.8

[bmcewen]

so i started retuning according to the lc-1 instead of ms gauge... huge difference( in a good way)
but ego is turned off and i imagine i couldn't use auto tune or ve analyzer...any more ideas how to fix this?

[trakkies]

You could check the voltage output of the LC-1 and make sure it agrees with what MS expects to see. And do the same with a Stim. That should show up where the error is occurring. Has the LC-1 got a test or emulator mode where it will output a constant voltage?

[bmcewen]

There deffinetly is a way to change the output voltage so that both outputs read the same constant voltage say 2.5 volts then i could figure out the ground offset difference between the two guages by what they were reading and offset one output to that they read the same, However i feel this is a bandaid not a fix. How do i go about fixing the ground offset issue?

[trakkies]

Can you get at your MS with the engine running? If so measure the voltage between the ground point on the block and the MS ground. If it is a grounding problem, such a large error should show up easily. Looking at the same thing with a scope grounded to the battery terminal would be good thing too - to check for any interference.

[bmcewen]

Ok Trakkies now this seems like a helpfull course of action but I'm confused on what you mean by Ms ground point...the only ground point I'm aware of is the wire going from the relay board to the engine block.

[bmcewen]

As far as the sillyscope goes I only have access to winscope but not really sure what to attach the wires to since I've never really used it before

[trakkies]

Ok Trakkies now this seems like a helpfull course of action but I'm confused on what you mean by Ms ground point...the only ground point I'm aware of is the wire going from the relay board to the engine block.

I'd try soldering a wire to the pin 1 tail of the connector inside MS, or any other suitable ground point inside MS. To be absolutely sure there is nothing going on between the relay board and MS. But it is clutching at straws.

[bmcewen]

found the cause i think, the voltage coming out of the two analog wires is not the same in open air one is 5v one is 4v both around programmed for 0-5v.....now have to figure out how to fix it