Wiring lc-1 into megasquirt.

[Scottinva]

How did you guys wire your LC-1 into your megasquirt. I went with the approach of putting the ms2 into the internal prongs of the factory ECU. The LC-1 itself doesn't look long enough? How did you guns run it to get it into the glovebox? Also did you share the grounds and use the stock ecu, so ms2 and lc-1 are grounded together? I know that one of the ms2 inputs has to be the lc-1 (obviously).

[Brad D.]

Just lengthen the analog output wire to reach where you need it to go. It doesn't need to be soldered to the pins of the Motronic box, just wire it right into the DB37 connector on MS. And yes, the LC-1 needs to be grounded to the same spot as MS-2 which should be tied into the grounds through the Motronic box and terminate on the engine(valve cover).

[Scottinva]

Okay so, did you run the wires down the drivers frame rail and go through the firewall and go across? Did you have to lengthen your wires? I have the idlebox and megasquirt all wired up to the ecu, all I need to do now is solder 2 wires on for the reference sensor and stick it in the glovebox and plug it in, once I do that I have to solder the lc-1 to the MS2 in the glovebox to the ms2 box correct? Also solder the wires on for the GM sensor

[M. Holtmeier]

I mounted mine on the left rail and ran it up and across the firewall. No wires were lengthened. Also, make sure to seperate the heater ground from the sensor ground. I tied my sensor ground with the ms ground and made a second ground bus available in the glove box for the heater ground.

[Brad D.]

Oh, also make sure you use shielded wire for your VR sensor wiring that you are adding. Take Mikes advice on mounting as I am using an LM-1, however wiring it into MS is the same.

[Scottinva]

Oh, also make sure you use shielded wire for your VR sensor wiring that you are adding. Take Mikes advice on mounting as I am using an LM-1, however wiring it into MS is the same.

Where can I buy shielded wire? What kind of length should I get?

[altus22]

Oh, also make sure you use shielded wire for your VR sensor wiring that you are adding. Take Mikes advice on mounting as I am using an LM-1, however wiring it into MS is the same.

Where can I buy shielded wire? What kind of length should I get?

I think this is the stuff I used. Allelectronics.com is a great place if you need other miscellaneous surplus electronic stuff. Check Cain Electronics at E Princess Anne and Ingleside too. Otherwise, I know Home Depot and Lowes have shielded wire by the foot.

Solder the shield lead (uninsulated wire) to ground and only strip back the shielding (aluminum foil) as much as needed.

[Scottinva]

Oh, also make sure you use shielded wire for your VR sensor wiring that you are adding. Take Mikes advice on mounting as I am using an LM-1, however wiring it into MS is the same.

Where can I buy shielded wire? What kind of length should I get?

I think this is the stuff I used. Allelectronics.com is a great place if you need other miscellaneous surplus electronic stuff. Check Cain Electronics at E Princess Anne and Ingleside too. Otherwise, I know Home Depot and Lowes have shielded wire by the foot.

Solder the shield lead (uninsulated wire) to ground and only strip back the shielding (aluminum foil) as much as needed.

Ya i'll head over and grab a few feet.

[russc]

Also,
Only ground the shield wire at one end of the cable. Perferably at the ECU end. That can help prevent ground loops.

RussC

Oh, also make sure you use shielded wire for your VR sensor wiring that you are adding. Take Mikes advice on mounting as I am using an LM-1, however wiring it into MS is the same.

Where can I buy shielded wire? What kind of length should I get?

I think this is the stuff I used. Allelectronics.com is a great place if you need other miscellaneous surplus electronic stuff. Check Cain Electronics at E Princess Anne and Ingleside too. Otherwise, I know Home Depot and Lowes have shielded wire by the foot.

Solder the shield lead (uninsulated wire) to ground and only strip back the shielding (aluminum foil) as much as needed.

[Scottinva]

Where were you guys mounting your lc-1 body, i'm thinking about just using double sided tape and tape it to the side of the left rail, and run the wires up across the firewall and go through the stock grommet.

[Patrick McHugh]

That's what I did, the grommet is a pain to deal with!

[Scottinva]

Alright I have all that settled, all the wires are in the glovebox, MS2 is wired to ECU, I have a shielded o2 wire from my MS2 for LC-1 o2 analog input, the other input from LC-1 is going to my AIR/FUEL gauge, but what about the grounds? Brad was trying to explain it to me but I didn't understand 100%. There are 5 grounds coming from MS2, and they all tie together to 1 wire about an inch after they leave MS2, that 1 wire is grounded to the ECU on prong 5. Do I need to ground the lc1 and my air/fuel gauge to the ecu unit as well to link all the ecu grounds? I don't totally understand. There are the 12v switched powers for both the LC-1 and Gauge also, is there a 12v switch source close in the glovebox I can tie into, it seems crazy to have now 4 12v switched on 1 prong in my ecu. The 4 being Gauge, lc1, idleboard, and MS2

[George]

Alright I have all that settled, all the wires are in the glovebox, MS2 is wired to ECU, I have a shielded o2 wire from my MS2 for LC-1 o2 analog input, the other input from LC-1 is going to my AIR/FUEL gauge, but what about the grounds? Brad was trying to explain it to me but I didn't understand 100%. There are 5 grounds coming from MS2, and they all tie together to 1 wire about an inch after they leave MS2, that 1 wire is grounded to the ECU on prong 5. Do I need to ground the lc1 and my air/fuel gauge to the ecu unit as well to link all the ecu grounds? I don't totally understand. There are the 12v switched powers for both the LC-1 and Gauge also, is there a 12v switch source close in the glovebox I can tie into, it seems crazy to have now 4 12v switched on 1 prong in my ecu. The 4 being Gauge, lc1, idleboard, and MS2

Ideally you would use a set of relay switches that runs off the ignition to power the components. That's what relays are good for. That will take care of the power source. Also, its a good idea to actually have all the components grounded at the same source, just as Brad suggested. If the wideband and MS are grounded at different points, there is the possibility of creating a voltage drop between the two units and this will alter the reading.

[Scottinva]

Alright I have all that settled, all the wires are in the glovebox, MS2 is wired to ECU, I have a shielded o2 wire from my MS2 for LC-1 o2 analog input, the other input from LC-1 is going to my AIR/FUEL gauge, but what about the grounds? Brad was trying to explain it to me but I didn't understand 100%. There are 5 grounds coming from MS2, and they all tie together to 1 wire about an inch after they leave MS2, that 1 wire is grounded to the ECU on prong 5. Do I need to ground the lc1 and my air/fuel gauge to the ecu unit as well to link all the ecu grounds? I don't totally understand. There are the 12v switched powers for both the LC-1 and Gauge also, is there a 12v switch source close in the glovebox I can tie into, it seems crazy to have now 4 12v switched on 1 prong in my ecu. The 4 being Gauge, lc1, idleboard, and MS2

Ideally you would use a set of relay switches that runs off the ignition to power the components. That's what relays are good for. That will take care of the power source. Also, its a good idea to actually have all the components grounded at the same source, just as Brad suggested. If the wideband and MS are grounded at different points, there is the possibility of creating a voltage drop between the two units and this will alter the reading.

Alright i'll ground everything to my ecu then, how exactly do I go about using a relay for my 12v switched. I'm extremely new at this stuff and almost need a step by step.

[Scottinva]

Can I put the IAT sensor on the intake manifold without heatsoak? I am running N/A for now so I don't have charge pipes or an intercooler to put it on.

[Brad D.]

I am not aware of anyone who has successfully put one in the intake. I think everyone ends up putting it in the charge piping. I thought you were going to put it in your AFM delete pipe.

[George]

Mine was originally mounted on the bottom of the manifold and then I moved to the charge pipe.

[M. Holtmeier]

Can I put the IAT sensor on the intake manifold without heatsoak? I am running N/A for now so I don't have charge pipes or an intercooler to put it on.

Yes, you will have heat soak and lean hot starts. I know of a function in MS I that allows for compensation, but I am still trying to get that just right on mine. For the most part it is corrected, but there are a few occasions where the engine stumbles slightly for ~5 seconds with an afr reading of 16 or so until fresh air reaches the sensor. I personally want to know my intake temp after the intercooler, so I will put up with it. I think some have installed two seperate sensors and made it possible to switch between the them, as you won't need to datalog temp after cooler all the time.

As far as wiring the relays, the easiest way to get switched power to several loads is to first get properly fused and sized 12v unswitched wiring to where your relays will mount. Then control each of them with an ignition (switched) source. For example, one relay would have a 16 or 18 ga. ign wire at pin 85 and a ground to chassis at pin 86, fused with something small like 5A. Your load would be placed on pin 87 and the unswitched source at pin 30, with something like a 20A fuse near the battery. Just make sure the load is properly fused and the appropriate sized wiring is used.

[Scottinva]

There was an inline fused cable that goes near the battery, I can just route it into the glovebox and use that for my gauge and lc1, and all the grounds for both go into my ecu box. I then have to make a delete pipe for the afm (somehow) and make a bung for my IAT sensor, how do I hack the afm wires to use the IAT on it, I couldn't find a wiring chart for the stupid thing. Also can't I wire MS2 to ECU for the crank sensor, and just use the stock flywheel sensor wires and somehow connect those to the crank sensor. I'm truely awful at this stuff, so understanding it is giving me a headache, I just learned how to solder yesterday let alone how to do this kind of wiring.

[Brad D.]

There was an inline fused cable that goes near the battery, I can just route it into the glovebox and use that for my gauge and lc1, and all the grounds for both go into my ecu box. I then have to make a delete pipe for the afm (somehow) and make a bung for my IAT sensor, how do I hack the afm wires to use the IAT on it, I couldn't find a wiring chart for the stupid thing. Also can't I wire MS2 to ECU for the crank sensor, and just use the stock flywheel sensor wires and somehow connect those to the crank sensor. I'm truely awful at this stuff, so understanding it is giving me a headache, I just learned how to solder yesterday let alone how to do this kind of wiring.

Dude, regarding the crank sensor, that's exactly what I told you last night. Use the stock flywheel wiring for one of the sensors. Splice the crank mounted VR sensor wiring into the original flywheel wiring and you are good to go. I would cut the plug off of one of the original reference sensors and splice that onto the new crank VR sensor that way it can be unplugged and replaced. As for the AFM wires, you can go by wire color, I specified them in the chart for that reason. The ETM will give you specific pin locations if that is what you want.

[Patrick McHugh]

Can I put the IAT sensor on the intake manifold without heatsoak? I am running N/A for now so I don't have charge pipes or an intercooler to put it on.

Yes, you will have heat soak and lean hot starts. I know of a function in MS I that allows for compensation, but I am still trying to get that just right on mine. For the most part it is corrected, but there are a few occasions where the engine stumbles slightly for ~5 seconds with an afr reading of 16 or so until fresh air reaches the sensor. I personally want to know my intake temp after the intercooler, so I will put up with it. I think some have installed two seperate sensors and made it possible to switch between the them, as you won't need to datalog temp after cooler all the time.

As far as wiring the relays, the easiest way to get switched power to several loads is to first get properly fused and sized 12v unswitched wiring to where your relays will mount. Then control each of them with an ignition (switched) source. For example, one relay would have a 16 or 18 ga. ign wire at pin 85 and a ground to chassis at pin 86, fused with something small like 5A. Your load would be placed on pin 87 and the unswitched source at pin 30, with something like a 20A fuse near the battery. Just make sure the load is properly fused and the appropriate sized wiring is used.

Why not put it in the shade below the car somewhere or in the bumper?

[Brad D.]

Can I put the IAT sensor on the intake manifold without heatsoak? I am running N/A for now so I don't have charge pipes or an intercooler to put it on.

Yes, you will have heat soak and lean hot starts. I know of a function in MS I that allows for compensation, but I am still trying to get that just right on mine. For the most part it is corrected, but there are a few occasions where the engine stumbles slightly for ~5 seconds with an afr reading of 16 or so until fresh air reaches the sensor. I personally want to know my intake temp after the intercooler, so I will put up with it. I think some have installed two seperate sensors and made it possible to switch between the them, as you won't need to datalog temp after cooler all the time.

As far as wiring the relays, the easiest way to get switched power to several loads is to first get properly fused and sized 12v unswitched wiring to where your relays will mount. Then control each of them with an ignition (switched) source. For example, one relay would have a 16 or 18 ga. ign wire at pin 85 and a ground to chassis at pin 86, fused with something small like 5A. Your load would be placed on pin 87 and the unswitched source at pin 30, with something like a 20A fuse near the battery. Just make sure the load is properly fused and the appropriate sized wiring is used.

Why not put it in the shade below the car somewhere or in the bumper?

He is referring to the intake air temp sensor that must be added for MS to calculate air density. It has to be in the intake stream, and on a turbo car, after the intercooler. The problem with placing it in the metal intake mani is that it suffers from heat soak as the hot metal intake bleeds heat into the sensor body sending false info to MS creating a lean condition. It is much less susceptible to heat soak if it is in a charge pipe.

[M. Holtmeier]

Buy a Bentley manual if you don't already have one. You can also download an e28 etm to get the wiring diagrams. Think of this though; if you are eliminating the afm, every one of those wires, as long as the harness is in good condition, is a fine candidate to use for your iat circuit. All you need to do really is measure the resistance from the afm conn and ecu conn to make sure you have 2 wires you like(not a ground) and connect the MS db37 iat to the ECU pins you choose. Double check that the two wires you choose for the circuit show no resistance to ground.

It's been awhile since I wired mine, it's pretty hacked up too as I tried to use a piggy back before I went with MS. I do remember that most all the power and grounds are stock. The fuel pump and O2 is controlled bt MS where it cycles on initial key on then only turns on when MS sees an rpm signal. If you mount the wideband as part of the car, you don't want the sensor heater powered with the engine not running.

Regarding the inline fused wires: You may want something a little more robust for running the w/b and ms. IIRC, those wires are maybe 14ga?


EDIT: Damn I must type slow! Brad's beat me to the punch!

[Scottinva]

Well that wire will work for now. Any idea where I can find the 3" intake pipe on the cheap at a store? Also why does the o2 sensor wire have to be shielded when coming from lc-1 its just normal wire. So since there are 2 strands of shielded wire going to the flywheel sensors. Each having 2 wires, I will need 1 of those for ms-2 to ecu, and the other will splice into the crank sensor that is already on the car is that correct?

[Brad D.]

Just buy some 3" exhaust pipe and weld up a tube to delete the AFM. The o2 signal wire really doesn't have to be shielded, only the crank trigger wires.

[Scottinva]

There are two plugs going to the flywheel sensor, since there are 2 sensors. Which plug or both do I need to splice into for the crank sensor. I tried finding the afm and that wiring diagram, but I can't find them in the bentley unless i'm doing something wrong....

[Brad D.]

For clarification, go by wire color on the AFM, however the GY/VI wire is pin 1, the GY/BU wire is pin 4, those are the ones you need to use for your GM IAT sensor. You only need one sensor. The pins that I have denoted for the VR sensor, Motronic pins 25 and 26 are for the reference sensor, the grey plug. These are some small additions I will make to the wiring guide in the FAQ for future reference.