LC-1 with gauge

[RC4U12]

I tried the wiring like Matt suggested which was white from gauge to brown{which also goes to MS ecu} and red to power and black to ground{same as lc-1 ground} yellow to headlight i didnt hook up..
So with this the gauge reads higher than the mega tune or tuner studio screen..so i hook up the yellow wire from lc-1 to white on gauge and then it was oppistie..i found out that was programed for narrow band. i reprogramed to be same as brown wire and now both the gauge and megatune read in the 11's where i used to be 13's ...so i hook up logworks and it shows 13's....
what happened from trying this?? why do my gauge and megatune ortuner studio not read the same and why so far off of logworks?? Jeff

[oughtsix]

Hi Jeff,

I have the same exact problem. Which means that it could be only one thing, those darned 450slc's!

I have an Old 50's vintage westinghouse analogue 0-3v meter that is spot on with my Tektronix multimeter. Both of them read about a half volt high of what Logworks and megatune read. I assume it has something to do with the internal resistance of the meter vs. the internal resistance of the A/D chip in the MegaSquirt? Just a WAG though. I have one of the LC-1 analogue outputs setup for 0-5v and connected up to the MegaSquirt. I have the other setup for 0-2.8v connected up to my analogue meter. This puts the needle straight up at lambda = 1. The meter is just a visual reference anyway. I can see the notchiness of the lack of resolution in the LC-1 D/A converter as the meter always jumps a set distance when logworks reads just a bit high or low of lambda = 1 (stoic or however it is spelled).

I wonder what would happen if I put a 1 megaohm resister in parallel with my meter to simulate a lower internal resistance?

I seems like there needs to be a much better way of interfacing a wideband O2 with Megasquirt than the LC-1 (and ever other aftermarket wideband controller I am aware of) making analogue readings off the sensor, processing them digitally, supplying an analogue output to megasquirt which then converts it back to digital. This seems like a perfect problem for the CAN bus. It makes me wonder if some weird car has a wideband controller that outputs to the CAN bus which could be harvested and hacked? I am WAG'ing that most OEM computers have Wideband controllers on their ECU's?

[Matt Cramer]

I tried the wiring like Matt suggested which was white from gauge to brown{which also goes to MS ecu} and red to power and black to ground{same as lc-1 ground} yellow to headlight i didnt hook up..
So with this the gauge reads higher than the mega tune or tuner studio screen..so i hook up the yellow wire from lc-1 to white on gauge and then it was oppistie..i found out that was programed for narrow band. i reprogramed to be same as brown wire and now both the gauge and megatune read in the 11's where i used to be 13's ...so i hook up logworks and it shows 13's....
what happened from trying this?? why do my gauge and megatune ortuner studio not read the same and why so far off of logworks?? Jeff

My first thought is a ground offset. Where is the LC-1 grounded, and where is the MS grounded?

[RC4U12]

Matt I actually have the lci and gauge grounded same soldered end.and ms to the battery with cable going to the same bolt as the lc1 on the manifold.

[Matt Cramer]

I'm having trouble following that description. Could you sketch up a picture of your ground routing?

[RC4U12]

Sorry it took so long to get back but weve had two blizzards in a week and on top of that last week the Missouri river overflowed and flooded which hasnt happened since they installed garrison damn..
any wah will explain better as i dont know how to sketch and paste..
the ground wire from Lc-1 and the ground from the gauge are soldered to a round connector and bolted to the intake manifold{same place the old injector grounds were} the megasquirt ground wire is soldered to the battery terminal wire end{the big lead connector that goes to battery} and then a ground from the battery to the intake also..hope that helps...Jeff

[Matt Cramer]

That grounding is likely to give you a ground offset. You should either ground both directly to the battery or both directly to the engine block.